Weak ferromagnetism and spin-glass-like behavior in the rare-earth cupratesR2CuO4

Raman and weak ferromagnetism in Eu2CuO4

“…The peaks at 413cm -1 for XX polarization and 398 cm-1 for XY polarization, which we label B*g and B'g, respectively [10,11], do not correspond to any mode allowed in the T' structure. We tentatively attribute them to local modes associated with oxygen displacements in the CuO2 planes [7,8]. The intensity of the B*g peak, relative to the Big mode, is greater for samples grown in Pt/PbO than for those grown in A1203/CuO.…”

“…It was argued that a lateral displacement of the oxygen ions O(1) away from their symmetric positions in the CuO2 planes gives rise to an antisymmetric Dzyaloshinsky-Moriya exchange interaction between the Cu moments [7,8]. This distortion may also be responsible for the extra Raman lines seen in Nd2-xGdxCuO4 [9] and Gd2CuO 4 [10,11].…”

Structural Properties and Oxygen Stoichiometry of (Pr1.5Ce0.5)Sr2Cu2TaO10−δand (R1.5−xPrxCe0.5)Sr2Cu2NbO10−δ,R=Nd, Sm, Eu: Correlations with Electronic and Magnetic Properties

“…Furthermore, in those compounds which are doped and expected to be superconducting, namely PrBa Cu O , (Pr Ce )SCNO, and (Pr Ce )SCTO, the anomalous Pr magnetism and 4f-electronic interactions have been linked to the mechanism responsible for the suppression of superconductivity. For both superexchange and f-electronic interactions, the overlaps of the Pr 4f and CuO planar O 2p electronic wave functions, and therefore the Pr-oxygen bond length, are expected to be critical parameters of these interactions (15-17, 22, 27, 38-40) (42)(43)(44). The WF behavior has been attributed to a canting of the ordered Cu moments away from strictly antiferromagnetic (AF) alignment under the influence of asymmetric exchange interactions as discussed by Dzyaloshinsky and Moriya (45).…”

“…The WF behavior has been attributed to a canting of the ordered Cu moments away from strictly antiferromagnetic (AF) alignment under the influence of asymmetric exchange interactions as discussed by Dzyaloshinsky and Moriya (45). Inherent in this proposed model for WF in these tetragonal compounds is an assumption that the Cu-O coordination is not square-planar due to local distortions of the crystal structure since in a strictly square-planar structure such asymmetric couplings should not exist (42)(43)(44)(45). In the RCO compounds there is to date no clear evidence of such local structural distortions.…”

Dispersion of quasi-particles in high T c cuprates

“…Two classes of materials have been in the center of studies : heavy fermion systems and high T c superconductors. It is observed that in La 2-x Sr x CuO 4 SC occurs for a fairly wide range of doping, 0.05 ≤ x ≤ 0.25 while in electron doped successor like Nd 2-x Ce x CuO 4 superconductivity is known to occur only in the narrow concentration range x = 0.15 [1,2]. Besides, SC has not been observed for Gd 2-x Ce x CuO 4 although T ′ structure forms for 0 < x < 0.15.…”