{"id":10,"date":"2015-02-19T10:23:44","date_gmt":"2015-02-19T08:23:44","guid":{"rendered":"http:\/\/phsites.technion.ac.il\/magnetic\/?page_id=10"},"modified":"2023-03-21T10:40:40","modified_gmt":"2023-03-21T08:40:40","slug":"superconductivity","status":"publish","type":"page","link":"https:\/\/phsites.technion.ac.il\/magnetic\/research-activity\/superconductivity\/","title":{"rendered":"High Tc Superconductivity"},"content":{"rendered":"\n<div class=\"wp-block-group\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<h2 class=\"wp-block-heading\"> Common energy scale for magnetism and superconductivity in the cuprates <\/h2>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-media-text alignfull\"><figure class=\"wp-block-media-text__media\"><img loading=\"lazy\" decoding=\"async\" width=\"334\" height=\"417\" src=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/H_T_2.gif\" alt=\"\" class=\"wp-image-15 size-full\"\/><\/figure><div class=\"wp-block-media-text__content\">\n<p class=\"has-normal-font-size\"> One of the most challenging tasks of solid-state physics today is to understand the mechanism for superconductivity in cuprates. These materials, which have a relatively high critical temperature T<sub>c<\/sub>, are based on doped CuO<sub>2<\/sub> planes. Since at zero doping they are antiferromagnets, several theories ascribe their superconductivity to holes interacting via a magnetic medium. Yet the phenomenon of superconductivity begins at doping levels in which magnetism almost disappears, and therefore there is no clear evidence relating the two. Fortunately, there is a narrow doping range in which superconductivity and magnetism, in the form of randomly oriented static spins, co-exist below a critical temperature T<sub>g<\/sub>&lt;T<sub>c<\/sub>. We thus focus on this doping range and examine T<sub>g<\/sub> and T<sub>c<\/sub> in numerous superconducting families. We find that in all cases a common energy scale controls both critical temperatures. This is demonstrated in the figure where we plot both T<sub>c<\/sub>\/T<sub>c<\/sub><sup>max<\/sup> and T<sub>g<\/sub>\/T<sub>c<\/sub><sup>max<\/sup> as a function of holes in the system. In this normalized plot all data points of T<sub>c<\/sub> and T<sub>g<\/sub>, for various materials, collapse into a single curve. This clearly indicates that superconductivity and magnetism in the cuprates share a common energy scale. <\/p>\n<\/div><\/div>\n\n\n\n<h3 class=\"wp-block-heading\">We have published the following papers on the subject: <\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li> D.S.Ellis, Yao-Bo Huang, P.Olalde-Velasco, M.Dantz, J.Pelliciari, G Drachuck, R.Ofer, G. Bazalitsky, J. Berger, T.Schmitt, and A.Keren, <a href=\"http:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/PhysRevB.92.104507-1.pdf\">Correlation of the superconducting critical temperature with spin and orbital excitations in (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> as measured by resonant inelastic x-ray scattering<\/a>, Phys. Rev. B 92, (2015) 104507. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>Electronic spin and orbital (dd) excitation spectra of (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> samples aremeasured by resonant inelastic x-ray scattering (RIXS). In this compound, Tc of samples with identical hole dopings is strongly affected by the Ca\/Ba substitution x due to subtle variations in the lattice constants, while crystal symmetry and disorder as measured by linewidths are x independent. We examine two extreme values of x and two extreme values of hole-doping content y corresponding to antiferromagnetic and superconducting states. The x dependence of the spin-mode energies is approximately the same for both the antiferromagnetic and superconducting samples. This clearly demonstrates that RIXS is sensitive to the superexchange J even in doped samples. A positive correlation between J and the maximum of T<sub>c<\/sub> at optimal doping (T<sub>c<\/sub><sup>max<\/sup>) is observed. We also measured the x dependence of the d<sub>xy<\/sub> \u2192 d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub> and d<sub>xz\/yz<\/sub> \u2192 d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub> orbital splittings. We infer that the effect of the unresolved d<sub>3z<sup>2<\/sup>-r<sup>2<\/sup><\/sub> \u2192 d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub> excitation on T<sub>c<\/sub><sup>max<\/sup> is much smaller than the effect of J . There appears to be dispersion in the d<sub>xy<\/sub> \u2192 d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub> peak of up to 0.05 eV. Our fitting furthermore indicates an asymmetric dispersion for the d<sub>xz\/yz<\/sub> \u2192 d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub> excitation. A peak at ~ 0.8 eV is also observed and attributed to a dd excitation in the chain layer. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> D.Wulferding, M.Shay G.Drachuck, R.Ofer, G.Bazalitsky, Z.Salman, P.Lemmens, and A.Keren, <a href=\"http:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Relation-between-cuprate-superconductivity-and-magnetism.pdf\">Relation between cuprate superconductivity and magnetism: A Raman study of (CaLa)<sub>1<\/sub>(BaLa)<sub>2<\/sub>Cu<sub>3<\/sub>O<sub>y<\/sub><\/a>, Phys. Rev. B 90, (2014) 104511. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We present an investigation of charge-compensated antiferromagnetic (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> single crystals using Raman scattering as well as muon spin rotation. In this system the parameter x controls the Cu-O-Cu superexchange interaction via bond distances and buckling angles. The oxygen content y controls the charge doping. In the absence of doping the two-magnon peak position is directly proportional to the superexchange strength J. We find that both x and y affect the peak position considerably. The N\u00e9el temperature determined from muon spin rotation on the same samples independently confirms the strong dependence of the magnetic interaction on x and y. We find a considerable increase in the maximum superconducting transition temperature T<sub>c<\/sub><sup>max<\/sup> with J. This is strong evidence of the importance of orbital overlap to superconductivity in this family of cuprates. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> T.Cvitani\u0107, D.Pelc, M.Po\u017eek, E.Amit, and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/17O-NMR-Knight-shift-study-of-the-interplay-between-superconductivity-and-pseudogap.pdf\"><sup>17<\/sup>O-NMR Knight shift study of the interplay between superconductivity and pseudogap in&nbsp; (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub><\/a>, Phys. Rev. B 90, (2014) 054508 . <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We report systematic 17O-NMR measurements on the high-Tc cuprate (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub>,  for four different families (different x). Using Knight shift data, we  show that the pseudogap opening temperature T* is much higher than T<sub>c<\/sub>  near optimal doping, unlike structurally similar YBCO. In addition, at  constant doping the pseudogap temperature does not vary with x, in  contrast to T<sub>c<\/sub>. This puts constraints on the nature of the  pseudogap and position of the quantum critical point inside the  superconducting dome. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> G.Drachuck, E.Razzoli, R.Ofer, G.Bazalitsky, R.S.Dhaka, A.Kanigel, M.Shi, and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Linking-dynamic-and-thermodynamic-properties-of-cuprates.pdf\">Linking dynamic and thermodynamic properties of cuprates: An angle-resolved photoemission study of (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> (x = 0.1 and 0.4)<\/a>, Phys. Rev. B 89, (2014) 121119(R). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We report angle-resolved photoemission spectroscopy on two families of high-temperature superconductors (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> with x = 0.1 (T<sub>c<\/sub><sup>max<\/sup> = 56 K) and x = 0.4 (T<sub>c<\/sub><sup>max<\/sup>  = 82 K). The Fermi surface (FS) is found to be independent of x or y,  and its size indicates extreme sample-surface overdoping. This universal  FS allows the comparison of dynamical properties between  superconductors of similar structure and identical doping, but different  Tcmax. We find that the high-energy (|E| &gt; 50 meV) nodal velocity in  the x = 0.4 family is higher than in the x = 0.1 family. The implied  correlation between Tcmax and the hopping rate t supports the notion of  kinetic energy driven superconductivity in the cuprates. We also find  that the antinodal gap is higher for the x = 0.4 family. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> G.Drachuck, E.Razzoli, G.Bazalitski, A.Kanigel, C.Niedermayer, M.Shi, and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Comprehensive-study-of-the-spin-charge-interplay-in-antiferromagnetic-La2-xSrxCuO4.pdf\">Comprehensive study of the spin-charge interplay in antiferromagnetic La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub><\/a>, Nature Communications 5, Article number: 3390, February (2014). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>The origin of the pseudogap and its relationship with  superconductivity in the cuprates remains vague. In particular, the  interplay between the pseudogap and magnetism is mysterious. Here we  investigate the newly discovered nodal gap in hole-doped cuprates using a  combination of three experimental techniques applied to one, custom  made, single crystal. The crystal is an antiferromagnetic La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub>  with x = 1.92%. We perform angleresolved photoemission spectroscopy  measurements as a function of temperature and find: quasi-particle  peaks, Fermi surface, anti-nodal gap and below 45 K a nodal gap. Muon  spin rotation measurements ensure that the sample is indeed  antiferromagnetic and that the doping is close, but below, the  spin-glass phase boundary. We also perform elastic neutron scattering  measurements and determine the thermal evolution of the commensurate and  incommensurate magnetic order, where we find that a nodal gap opens  well below the commensurate ordering at 140 K, and close to the  incommensurate spin density wave ordering temperature of 30 K. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> S.Asban, M.Shay, M.Naamneh, T.Kirzhner, and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Strong-versus-weak-coupling-paradigms-for-cuprate-superconductivity.pdf\">Strong- versus weak-coupling paradigms for cuprate superconductivity<\/a>, Phys. Rev. B 88, (2013) 060502 (R). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>Absolute resistivity measurements as a function of temperature from optimally doped YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub>7-\u03b4<\/sub> , La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub>, Bi<sub>2<\/sub>Sr<sub>2<\/sub>Ca<sub>1<\/sub>Cu<sub>2<\/sub>O<sub>8-x<\/sub>, and (Ca<sub>0.1<\/sub>La<sub>0.9<\/sub>)(Ba<sub>1.65<\/sub>La<sub>0.35<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> thin films are reported. Special attention is given to the measurement geometrical factors and the resistivity slope between T<sub>c<\/sub> and T*. The results are compared with a strong-coupling theory for the resistivity derivative near T<sub>c<\/sub>,  which is based on hard core bosons, and with several weak-coupling  theories, which are BCS based. Surprisingly, our results agree with both  paradigms. The implications of these findings and the missing  calculations needed to distinguish between the two paradigms are  discussed. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> E.Razzoli, G.Drachuck, A.Keren, M.Radovic, N.C.Plumb, J.Chang, J.Mesot, M.Shi, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Evolution-from-a-nodeless-gap-to-dx2-y2-wave-in-underdoped-La2-xSrxCuO4.pdf\">Evolution from a nodeless gap to d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub> \u2013 wave in underdoped La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub><\/a>, Phys. Rev. Lett., 110,&nbsp; (2013) 047004. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>Using angle-resolved photoemission spectroscopy (ARPES), it  is revealed that the low-energy electronic excitation spectra of highly  underdoped superconducting and nonsuperconducting La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub> cuprates are gapped along the entire underlying Fermi surface at low temperatures. We show how the gap function evolves to a d<sub>x<sup>2<\/sup>-y<sup>2<\/sup><\/sub>  form with increasing temperature or doping, consistent with the vast  majority of ARPES studies of cuprates. Our results provide essential  information for uncovering the symmetry of the order parameter(s) in  strongly underdoped cuprates, which is a prerequisite for understanding  the pairing mechanism and how superconductivity emerges from a Mott  insulator. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> G.Drachuck, M.Shay, G.Bazalitsky, Z.Salman, A.Amato, C.Niedermayer, D.Wulferding, P.Lemmens, and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/New-Perspectives-for-Cuprate-Research.pdf\">New Perspectives for Cuprate Research: A (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub><\/a> Single Crystal, J. Supercond. Nov. Magn., June (2012). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We report the successful growth of a large (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> (CLBLCO) single crystal. In this material, x controls the maximum of T<sub>c<\/sub> (T<sub>c<\/sub><sup>max<\/sup>), with minimal structural changes. Therefore, it allows a search for correlations between material properties and T<sub>c<\/sub><sup>max<\/sup>.  We demonstrate that the crystals are good enough for neutron scattering  and cleave well enough for Raman scattering. These results open new  possibilities for cuprate research. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> G. Drachuck, M. Shay, G. Bazalitsky, J. Berger, and A. Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Parallel-and-perpendicular-susceptibility-above-Tc-in-La2-xSrxCuO4-single-crystals.pdf\">Parallel and perpendicular susceptibility above Tc in La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub> single crystals<\/a>,Phys. Rev. B, 85, (2012) 184518. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We report direction-dependent susceptibility and resistivity measurements on La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub>  single crystals. These crystals have rectangular needle-like shapeswith  the crystallographic \u201cc\u201d direction parallel or perpendicular to the  needle axis, which, in turn, is in the applied field direction. At  optimal doping we find finite diamagnetic susceptibility above Tc,  namely fluctuating superconductivity (FSC), only when the field is  perpendicular to the planes. In underdoped samples we find FSC in both  field directions. We provide a phase diagram showing the FSC region,  although it is sample dependent in the underdoped cases. The variations  in the susceptibility data suggest a different origin for the FSC  between underdoping (below 10%) and optimal doping. Finally, our data  indicate that the spontaneous vortex diffusion constant above T<sub>c<\/sub> is anomalously high. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> E.Amit, A.Keren, J.S.Lord, and P.King, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/A-Precise-Measurement-of-the-Oxygen-Isotope-Effect-on-the-Neel-Temperature-in-Cuprates.pdf\">A Precise Measurement of the Oxygen Isotope Effect on the Neel Temperature in Cuprates<\/a>, Advances in Cond Matter Phys, (2011) 178190. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>A limiting factor in the ability to interpret isotope  effect measurements in cuprates is the absence of sufficiently accurate  data for the whole phase diagram; there is precise data for Tc , but not  for the antiferromagnetic transition temperature TN. Extreme  sensitivity of TN to small changes in the amount of oxygen in the sample  is the major problem. This problem is solved here by using the novel  compound (Ca<sub>0.1<\/sub>La<sub>0.9<\/sub>)(Ba<sub>1.65<\/sub>La<sub>0.35<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub>  for which there is a region where TN is independent of oxygen doping.  Meticulous measurements of TN for samples with 16O and 18O find the  absence of an oxygen isotope effect on TN with unprecedented accuracy. A  possible interpretation of our finding and existing data is that  isotope substitution affects the normal state charge carrier density. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> E.Razzoli1, Y.Sassa, G.Drachuck, M.Mansson, A.Keren, M.Shay,  M.H.Berntsen, O.Tjernberg, M.Radovic, J.Chang, S.Pailhes, N.Momono,  M.Oda, M.Ido, O.J.Lipscombe, S.M.Hayden, L.Patthey, J.Mesot and M.Shi, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/The-Fermi-surface-and-band-folding-in-La2-xSrxCuO4-probed-by-angle-resolved-photoemission.pdf\">The Fermi surface and band folding in La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub>, probed by angle-resolved photoemission<\/a>, New J. Phys., 12, (2010) 125003. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>A systematic angle-resolved photoemission study of the electronic structure of La<sub>2-x<\/sub>Sr<sub>x<\/sub>CuO<sub>4<\/sub>  in a wide doping range is presented in this paper. In addition to the  main energy band, we observed a weaker additional band, the (\u03c0, \u03c0)  folded band, which shows unusual doping dependence. The appearance of  the folded band suggests that a Fermi surface reconstruction is doping  dependent and could already occur at zero magnetic field. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> E.Amit and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Critical-doping-universality-for-cuprate-superconductors-Oxygen-nuclear-magnetic-resonance-investigation-of-CaxLa1-xBa1.75-xLa0.25xCu3Oy.pdf\">Critical-doping universality for cuprate superconductors: Oxygen nuclear-magnetic-resonance investigation of (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub><\/a>, Phys. Rev. B., 82, (2010) 172509. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>The critical doping levels in cuprates, where the ground  state changes its nature (from an antiferromagnet to a spin glass to  superconductor to metal), are not universal. We investigate the origin  of these critical doping variations by measuring the in-plane oxygen p\u03c3  hole density in the CuO2 layers as a function of the oxygen density y in  (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub>. This is done using the oxygen 17 nuclear quadrupole resonance parameter \u03bd<sub>Q<\/sub>.  We compare compounds with x=0.1 and 0.4 which have significant critical  y variations and find that these variations can be explained by a  change in the efficiency of hole injection into the <em>p<\/em><sub>\u03c3<\/sub>  orbital. This allows us to generate a unified phase diagram for the  CLBLCO system across the entire doping range, with no adjustable  parameters. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Evidence-of-magnetic-mechanism-for-cuprate-superconductivity.pdf\">Evidence of magnetic mechanism for cuprate superconductivity<\/a>, New J. Phys., 11, (2009) 065006. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>A proper understanding of the mechanism for cuprate  superconductivity can emerge only by comparing materials in which  physical parameters vary one at a time. Here, we present a variety of  bulk, resonance and scattering measurements on the (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub>  high temperature superconductors, in which this can be done. We  determine the superconducting, N\u00e9el, glass and pseudopage critical  temperatures. In addition, we clarify which physical parameter varies,  and, equally important, which does not, with each chemical modification.  This allows us to demonstrate that a single energy scale, set by the  superexchange interaction <em>J<\/em> , controls all the critical temperatures of the system. <em>J<\/em> , in turn, is determined by the in plane Cu-O-Cu buckling angle. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> R.Ofer and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Nutation-versus-angular-dependent-NQR-spectroscopy-and-impact-of-underdoping-on-charge-inhomogeneities-in-YBa2Cu3Oy.pdf\">Nutation versus angular-dependent NQR spectroscopy and impact of underdoping on charge inhomogeneities in YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub>y<\/sub><\/a>, Phys. Rev. B. 80, (2009) 224512. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We describe two different nuclear quadrupole resonance  (NQR) based techniques, designed to measure the local asymmetry of the  internal electric field gradient \u03b7 and the tilt angle \u03b1 of the main NQR  principal axis z^ from the crystallographic axis c^. These techniques  use the dependence of the NQR signal on the duration of the radio  frequency (rf) pulse and on the direction of the rf field H<sub>1<\/sub> with respect to the crystal axis. The techniques are applied to oriented powder of YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub>y<\/sub> fully enriched with <sup>63<\/sup>Cu.  Measurements were performed at different frequencies, corresponding to  different in-plane copper sites with respect to the dopant. Combining  the results from both techniques, we conclude that oxygen deficiency in  the chain layer lead to a rotation of the NQR main principal axis at the  nearby Cu on the CuO<sub>2<\/sub> planes by <em>\u03b1<\/em> \u2242 20\u00b0 \u2213 5\u00b0. This occurs with no change to <em>\u03b7<\/em>. The axis rotation associated with oxygen deficiency means that there must be electric field inhomogeneities in the CuO<sub>2<\/sub> planes only in the vicinity of the missing oxygen. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> M. Shai, A. Keren, G. Koren, A. Kanigel, O. Shafir, L. Marcipar, G.  Nieuwenhuys, E. Morenzoni, A. Suter, Th. Prokscha, M. Dubman, and D.  Podolsky, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Interaction-between-the-magnetic-and-superconducting-order-parameters-in-a-La1.94Sr0.06Cu4-wire-studied-via-muon-spin-rotation.pdf\">Interaction between the magnetic and superconducting order parameters in a La<sub>1.94<\/sub>Sr<sub>0.06<\/sub>Cu<sub>4<\/sub> wire studied via muon spin rotation<\/a>, Phys. Rev. B. 80, (2009) 144511. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We investigate the coupling between the magnetic and  superconducting order parameters in an 8-m-long meander line (\u201cwire\u201d)  made of a La<sub>1.94<\/sub>Sr<sub>0.06<\/sub>Cu<sub>4<\/sub> film with a cross section of 0.5 \u2715 100 \u03bcm<sup>2<\/sup>.  The magnetic order parameter is determined using the low-energy muon  spin relaxation technique. The superconducting order parameter is  characterized by transport measurements and modified by high current  density. We find that when the superconducting order parameter is  suppressed by the current, the magnetic transition temperature, T<sub>m<\/sub>,  increases. The extracted sign and magnitude of the Ginzburg-Landau  coupling constant indicate that the two orders are repulsive, and that  our system is located close to the border between first- and  second-order phase transition. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> R.Ofer, A.Keren, O.Chmaissem, and A.Amato, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Universal-doping-dependence-of-the-ground-state-staggered-magnetization-of-cuprate-superconductors.pdf\">Universal doping dependence of the ground-state staggered magnetization of cuprate superconductors<\/a>, Phys. Rev. B. 78, (2008) 140508(R). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>Using muon spin rotation we determine the zero-temperature staggered antiferromagnetic order parameter <em>M<\/em><sub>0<\/sub> versus hole doping measured from optimum \u0394<em>p<sub>m<\/sub><\/em>, in the (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> system. In this system the maximum T<sub>c<\/sub> and the superexchange <em>J<\/em> vary by 30% between families (<em>x<\/em>). <em>M<sub>0<\/sub><\/em>(<em>x,\u0394p<sub>m<\/sub><\/em>) is found to be x independent. Using neutron diffraction we also determine the lattice parameters variations for all <em>x<\/em> and doping. The oxygen buckling angle is found to change with <em>x<\/em>, implying a change in the holes kinetic energy. We discuss the surprising insensitivity of <em>M<sub>0<\/sub><\/em>(<em>x,\u0394p<sub>m<\/sub><\/em>) to the kinetic-energy variations in the framework of the <em>t-J<\/em> model. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> Y.Lubashevsky and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Experimental-investigation-of-the-origin-of-the-crossover-temperature-in-cuprate-superconductors-via-dc-magnetic-susceptibility.pdf\">Experimental investigation of the origin of the crossover temperature in cuprate superconductors via dc magnetic susceptibility<\/a>, Phys. Rev. B. 78, (2008) 020505(R). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We investigate the crossover temperature T* as a function of doping in (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub>, where the maximum T* (T<sub>c<\/sub><sup>max<\/sup>) varies continuously by 30% between families (<em>x<\/em>)  with minimal structural changes. T* is determined by dc-susceptibility  measurements. We find that T* scales with the maximum N\u00e9el temperature T<sub>N<\/sub><sup>max<\/sup>  of each family. This result strongly supports a magnetic origin of T*  and indicates that three dimensional interactions play a role in its  magnitude. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> R.Ofer, G.Bazalitsky, A.Kanigel, A.Keren, A.Auerbach, J.S.Lord, and A.Amato, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Magnetic-analog-of-the-isotope-effect-in-cuprates.pdf\">Magnetic analog of the isotope effect in cuprates<\/a>, Phys. Rev. B. 74, 220508(R) (2006). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We present extensive magnetic measurements of the (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> system with its four different families (<em>x<\/em>) having a T<sub>c<\/sub><sup>max<\/sup>(<em>x<\/em>)  variation of 28% and minimal structural changes. For each family, we  measured the N\u00e9el temperature, the anisotropies of the magnetic  interactions, and the spin-glass temperature. Our results exhibit a  universal relation T<sub>c<\/sub>=<em>cJn<sub>s<\/sub><\/em> for all families, where <em>c<\/em> ~ 1,<em> J<\/em> is the in-plane Heisenberg exchange, and <em>n<sub>s<\/sub><\/em>  is the superconducting carrier density. This relates cuprate  superconductivity to magnetism in the same sense that phonon-mediated  superconductivity is related to atomic mass. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A.Keren, A.Kanigel, and G.Bazalitsky, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Evidence-for-two-fluids-in-cuprate-superconductors-from-a-nuclear-resonance-study-of-CaxLa1-xBa1.75-xLa0.25xCu3Oy.pdf\">Evidence for two fluids in cuprate superconductors from a nuclear resonance study of (CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy<\/a>, Phys. Rev. B., 74,&nbsp; (2006) 172506. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We report charge density measurements, using NMR, in the superconducting compound (Ca<em><sub>x<\/sub><\/em>La<sub>1-<em>x<\/em><\/sub>)(Ba<sub>1.75-<em>x<\/em><\/sub>La<sub>0.25+<em>x<\/em><\/sub>)Cu<sub>3<\/sub>O<em><sub>y<\/sub><\/em>, which has two independent variables, <em>x<\/em> (family) and <em>y<\/em>  (oxygen). For underdoped samples we find the rate at which holes are  introduced into the plane upon oxygenation to be family independent. In  contrast, not all carriers contribute to either antiferromagnetic or  superconducting order parameters. This result is consistent with a  two-fluid phenomenology or intrinsic mesoscopic inhomogeneities in the  bulk. We also discuss the impact of weak chemical disorder on T<sub>c<\/sub>. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A.Kanigel and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/In-plane-hole-density-in-Ca0.1La0.9Ba1.65La0.35Cu3Oy-Nuclear-resonance-study-over-the-full-doping-range.pdf\">In-plane hole density in(Ca<sub>0.1<\/sub>La<sub>0.9<\/sub>)(Ba<sub>1.65<\/sub>La<sub>0.35<\/sub>)Cu<sub>3<\/sub>O<em><sub>y<\/sub><\/em>: Nuclear resonance study over the full doping range<\/a>, Phys. Rev. B. 74, (2006) 012505. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We report in-plane <sup>63<\/sup>Cu nuclear magnetic resonance measurements for a series of fully enriched (Ca<sub>0.1<\/sub>La<sub>0.9<\/sub>)(Ba<sub>1.65<\/sub>La<sub>0.35<\/sub>)Cu<sub>3<\/sub>O<em><sub>y<\/sub><\/em> powder samples, which belong to the YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub><em>y<\/em><\/sub>  (YBCO) family, but the doping could vary from very underdoped to  extremely overdoped. From these measurements, we determine the average  nuclear quadrupole resonance frequency <em>\u03bd<sub>Q<\/sub><\/em> and its second moment \u0394<em>\u03bd<sub>Q<\/sub><\/em>, both set by the in-plane hole density <em>n<\/em>, as a function of oxygen level <em>y<\/em>. We find that in the overdoped side <em>n<\/em> is saturated, but \u0394<em>\u03bd<sub>Q<\/sub><\/em> rapidly increases with increasing <em>y<\/em>. The relevance of these results to the increasing penetration depth in overdoped cuprates is discussed. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> R.Ofer, S.Levy, A.Kanigel and A.Keren, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Charge-inhomogeneity-doping-relations-in-YBa2Cu3Oy-detected-by-angle-dependent-nuclear-quadrupole-resonance.pdf\">Charge-inhomogeneity doping relations in YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub><em>y<\/em><\/sub> detected by angle-dependent nuclear quadrupole resonance<\/a>, Phys. Rev. B. 73, (2006) 012503. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>The origin of charge inhomogeneity in YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub><em>y<\/em><\/sub>  is investigated using an experimental method designed to determine the  nuclear quadrupole resonance (NQR) asymmetry parameter \u03b7 for very wide  NQR lines at different positions on the line. The method is based on the  measurement of the echo intensity as a function of the angle between  the radio frequency field H<sub>1<\/sub> and the principal axis of the electric field gradient. Static charge inhomogeneity deduced from <em>\u03b7<\/em>&gt;0  is found in this compound, but only in conjunction with oxygen  deficiency. This limits considerably the possible forms of charge  inhomogeneity in bulk YBa<sub>2<\/sub>Cu<sub>3<\/sub>O<sub><em>y<\/em><\/sub>. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A. Kanigel, A. Keren, A. Knizhnik, and O. Shafir, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Universal-linear-relations-between-susceptibility-and-Tc-in-cuprates.pdf\">Universal linear relations between susceptibility and T<sub>c<\/sub> in cuprates<\/a>, Phys. Rev. B. 71, (2005) 224511. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We develop an experimental method for measuring the intrinsic susceptibility <em>\u03c7<\/em>  of the powder of cuprate superconductors in the zero-field limit using a  dc magnetometer. The method is tested with lead spheres. Using this  method, we determine <em>\u03c7<\/em> for a number of cuprate families as a function of doping. A universal linear \u03c7 and not proportionality <em>\u03c7<\/em> relation between T<sub>c<\/sub> and <em>\u03c7<\/em> is found. We suggest possible explanations for this phenomenon. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> P. Carretta, A. Keren, J. S. Lord, I. Zucca, S. M. Kazakov, and J. Karpinski, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Anomaly-in-YBa2Cu4O8-charge-distribution-below-Tc-A-zero-field-muon-spin-relaxation-study.pdf\">Anomaly in YBa<sub>2<\/sub>Cu<sub>4<\/sub>O<sub>8<\/sub> charge distribution below T<sub>c:<\/sub> A zero-field muon spin relaxation study<\/a>, Phys. Rev. B. 71, (2005) 052507. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>Zero-field muon spin-relaxation (\u00b5SR) measurements in <sup>63<\/sup>Cu isotope enriched and natural YBa<sub>2<\/sub>Cu<sub>4<\/sub>O<sub>8<\/sub> powders are presented. The \u00b5<sup>+<\/sup>  relaxation rate is characterized by a sizeable enhancement as the  temperature is lowered below the superconducting transition temperature T<sub>c<\/sub>. The comparison of the asymmetry decay in the two samples reveals that the \u00b5<sup>+<\/sup>  relaxation is driven by nuclear dipole interaction from 300 K down to  4.2 K. It is argued that the increase in the relaxation rate below T<sub>c<\/sub> originates from a change either of the \u00b5<sup>+<\/sup>  site or of the orientation of the electric-field gradient at the Cu  nuclei, due to a modification in the charge distribution within CuO  chains. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A.Kanigel, A.Keren, L.Patlagan, K.B.Chashka and P.King,&nbsp;<a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Kanigal_PRL_92_04.pdf\">Muon Spin Relaxation Measurements of Na<sub>x<\/sub> CoO<sub>2<\/sub>* y H<sub>2<\/sub>O<\/a>, Phys. Rev. Lett. 92, (2004) 257007.&nbsp; <\/li>\n<\/ul>\n\n\n\n<div class=\"wp-block-media-text alignwide\"><figure class=\"wp-block-media-text__media\"><img loading=\"lazy\" decoding=\"async\" width=\"310\" height=\"320\" src=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/PRL_92_25_04.gif\" alt=\"\" class=\"wp-image-17 size-full\"\/><\/figure><div class=\"wp-block-media-text__content\">\n<p> Abstract:<\/p>\n\n\n\n<p>Using\n the transverse field muon spin relaxation technique,we measure the \ntemperature dependence of the magnetic field penetration depth ,i n the \nNa<sub>x<\/sub> CoO<sub>2<\/sub> y H<sub>2<\/sub> O system.We find that \n,which is determined by the superfluid density n s and the effective \nmass m ,is very small and on the edge of the TF-mSR \nsensitivity.Nevertheless,the results indicate that this system obeys the\n Uemura relation.By comparing with the normal state electron density,we \nconclude that m of the superconductivity carrier is 70 times larger than\n the mass of bare electrons.Finally,the order parameter in this system \ncannot be described by a complete gap over the entire Fermi surface.\n\n<\/p>\n<\/div><\/div>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A. Keren and A. Kanigel, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Keren_PRB_68_03.pdf\">Common energy scale for magnetism and superconductivity in cuprates<\/a>, Phys. Rev. B 68, 12507 (2003). <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>Many compounds based on CuO<sub>2<\/sub> planes (cuprates) superconduct below a critical temperature T<sub>c<\/sub>.&nbsp;Some of them show a second phase where a spontaneous static magnetic field appears below a critical temperature T<sub>g<\/sub>, which is lower than T<sub>c<\/sub>.&nbsp;By comparing T<sub>c<\/sub> and T<sub>g<\/sub> in numerous superconducting families,each with its own maximum T<sub>c<\/sub>,we  find that the same energy scale determines both critical  temperatures.&nbsp;This clearly indicates that the origin of  superconductivity in the cuprates is magnetic. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> Amit Keren, Amit Kanigel, James S. Lord, and Alex Amato, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Keren_SSC_03.pdf\">Universal superconducting and magnetic properties of the (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> system: a mSR investigation<\/a>, Solid State Commun. 126, (2003) 39. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>The (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub>  &nbsp;system is ideal for testing theories of high temperature  superconductivity, since nearly the full range of doping is controlled  by y, and T<sub>c<\/sub><sup>max<\/sup> is continuously controlled by x,  with minimal structural changes. We investigate this system with both  transverse and longitudinal field&nbsp;mSR. This allows us to re-examine the  Uemura relation, the nature of the spontaneous magnetic fields below Tc,  and the relation between their appearance temperature T<sub>g<\/sub> and T<sub>c<\/sub><sup>max<\/sup>. Our major findings are: (1) the Uemura relation is respected by this system more adequately than by other cuprates, (2) T<sub>g<\/sub> and T<sub>c<\/sub>  are controlled by the same energy scale, (3) the phase separation  between hole poor and hole rich regions is a microscopic one, and (4)  spontaneous magnetic fields appear gradually with no moment size  evolution.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A. Kanigel, A. Keren, Y. Eckstein, A. Knizhnik, J. S. Lord, and A. Amato, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Kanigel_PRL_02.pdf\">Common energy scale for magnetism and superconductivity in underdoped cuprates: a m SR investigation of (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub><\/a>, Phys. Rev. Lett. 88,&nbsp; (2002) 137003.&nbsp; <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We characterize the spontaneous magnetic field, and determine the associated temperature T<sub>g<\/sub>, in the superconducting state of (Ca<sub>x<\/sub>La<sub>1-x<\/sub>)(Ba<sub>1.75-x<\/sub>La<sub>0.25+x<\/sub>)Cu<sub>3<\/sub>O<sub>y<\/sub> using zero and longitudinal field&nbsp;mSR measurements for various values of x and y. Our major findings are: (I) T<sub>g<\/sub> and T<sub>c<\/sub>  are controlled by the same energy scale, (II) the phase separation  between hole poor and hole rich regions is a microscopic one, and (III)  spontaneous magnetic fields appear gradually with no moment size  evolution. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A. Keren, H. Alloul, P. Mendels, Y. Yoshinari, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Keren_PRL_97.pdf\">NMR study of <sup>17<\/sup>O transverse relaxation in YBa<sub>2<\/sub>Cu<sub>3<\/sub>(<sup>16<\/sup>O<sub>1-c<\/sub><sup>17<\/sup>O<sub>c<\/sub>)<sub>7<\/sub><\/a>, Phys.Rev. Lett. 78, (1997) 3547-3550. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>NMR transverse relaxation (TR) measurements of <sup>17<\/sup>O in the O(2,3) sites of YBa<sub>2<\/sub>Cu<sub>3<\/sub>(<sup>16<\/sup>O<sub>1-c<\/sub><sup>17<\/sup>O<sub>c<\/sub>)<sub>7<\/sub>  are presented. A Gaussian-like relaxation is found. The origin of this  relaxation is investigated by varying the isotopic concentration of the  oxygen, the temperature, the external field, and by comparing it with  the O(4) site. Our results are consistent with a model in which this  relaxation is caused by the dynamical fluctuation of copper nuclei,  including both spin lattice and flip-flop processes. With this model we  can explain consistently the TR of <sup>89<\/sup>Y and <sup>63,65<\/sup>Cu(1) as well. We use our results to re-analyze previous NMR <sup>63,65<\/sup>Cu(2) TR data. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A. Keren, L. P. Le, G. L. Luke, B. J. Sternlieb, W. D. Wu, Y. J. Uemura, S. Tajima, and S. Uchida, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Keren_PRB_93.pdf\">Muon Spin Rotation Measurements in Infinite Layer and Infinite Chain Cuprate Antiferromagnets: Ca<sub>0.86<\/sub>Sr<sub>0.14<\/sub>CuO<sub>2<\/sub> and Sr<sub>2<\/sub>CuO<sub>3<\/sub><\/a>, Phys. Rev. B 48, (1993) 12926-12935. <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We have performed zero-field muon spin rotation (mSR) measurements of the \u201cinfinite layer\u201d cuprate compound Ca<sub>0.86<\/sub>Sr<sub>0.14<\/sub>CuO<sub>2<\/sub>and the \u201cinfinite chain\u201d system Sr<sub>2<\/sub>CuO<sub>3<\/sub>. A spontaneous magnetic field from the ordered Cu moments is observed below T<sub>N<\/sub>=540(5)K in Ca<sub>0.86<\/sub>Sr<sub>0.14<\/sub>CuO<sub>2<\/sub>:  below T=360 K, we observe muon spin precession with a frequency&nbsp;n  (T-&gt; 0)=16 MHz (corresponding to a local field of 1.2 kG). The  precession signal is replaced by a rapid depolarization above T=360~K  due to the onset of muon diffusion. The hopping rate followed an  Arrhenius law, with an activation energy of E<sub>a<\/sub>=0.39(1) eV. The sub-lattice magnetization M<sub>s<\/sub>, proportional to&nbsp;n(T), showed a slower decay with increasing temperature in Ca<sub>0.86<\/sub>Sr<sub>0.14<\/sub>CuO<sub>2<\/sub>, compared with that observed in La<sub>2<\/sub>CuO<sub>4<\/sub> and Sr<sub>2<\/sub>CuO<sub>2<\/sub>C<sub>l2<\/sub>, indicating that a wider CuO<sub>2<\/sub> layer separation results in more 2-dimensional magnetic behavior. In the \u201cinfinite chain\u201d system Sr<sub>2<\/sub>CuO<sub>3<\/sub>,  the onset of magnetic order was found at T~5 K with a local field of  ~30 G at the muon site at T-&gt;0. The exchange interaction, inferred  from susceptibility measurements is on the order of 10<sup>3<\/sup> K, implying a remarkable suppression of the ordering temperature with k<sub>B<\/sub>T<sub>N<\/sub>\/J&lt;=0.01 in Sr<sub>2<\/sub>CuO<sub>3. <\/sub>These results demonstrate clear signatures of low dimensional magnetic behavior in the CuO chains. <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li> A. Keren, K. Kojima, L. P. Le, G. L. Luke, W. D. Wu, Y. J. Uemura, S. Tajima and S. Uchida, <a href=\"https:\/\/phsites.technion.ac.il\/magnetic\/wp-content\/uploads\/sites\/26\/2015\/02\/Keren_JMMM_95b.pdf\">Muon-Spin-Rotation Measurements in the \u2018Infinite-Chain\u2019 Ca<sub>2<\/sub>CuO<sub>3<\/sub><\/a>, JMMM 140-144 (1995) 1641-1642.  <\/li>\n<\/ul>\n\n\n\n<p> Abstract:<br>We performed zero-field muon-spin-rotation measurements of the \u201cinfinite-chain\u201d compound Ca<sub>2<\/sub>CuO<sub>3<\/sub>.  A spontaneous magnetic field is observed below 13 K. The exchange  interaction inferred from susceptibility measurements and two-magnon  Raman scattering is approximately 10<sup>3<\/sup> K, which implies a remarkable suppression of the ordering temperature k<sub>B<\/sub>T<sub>N<\/sub>\/J<sub>1d<\/sub>~0.01. We discuss the relevance of these measurements to the problem of one dimensional spin-1\/2 antiferromagnets. <\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Common energy scale for magnetism and superconductivity in the cuprates One of the most challenging tasks of solid-state physics today is to understand the mechanism for superconductivity in cuprates. These materials, which have a relatively high critical temperature Tc, are based on doped CuO2 planes. Since at zero doping they are antiferromagnets, several theories ascribe [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":15,"parent":8,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"class_list":{"0":"post-10","1":"page","2":"type-page","3":"status-publish","4":"has-post-thumbnail","6":"entry"},"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>High Tc Superconductivity - Magnetism Group<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/phsites.technion.ac.il\/magnetic\/research-activity\/superconductivity\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"High Tc Superconductivity - Magnetism Group\" \/>\n<meta property=\"og:description\" content=\"Common energy scale for magnetism and superconductivity in the cuprates One of the most challenging tasks of solid-state physics today is to understand the mechanism for superconductivity in cuprates. These materials, which have a relatively high critical temperature Tc, are based on doped CuO2 planes. 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