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Antiferromagnetism in YBa/sub 2/Cu/sub 3/O/sub 6+x/

Conference ·
OSTI ID:7192573
A number of models for high temperature superconductivity in the layered cuprate perovskites require strong antiferromagnetic superexchange interactions between Cu atoms. The existence of such interactions in La/sub 2/CuO/sub 4-y/ has previously been demonstrated. In this paper a review is given of recent neutron scattering work performed at Brookhaven studying antiferromagnetism in RBa/sub 2/Cu/sub 3/O/sub 6+x/ with R = Y, Nd. Measurements on ceramic samples with a range of oxygen concentrations have shown that 3D antiferromagnetic ordering of the Cu spins occurs throughout the nonsuperconducting tetragonal phase, corresponding to O less than or equal to x /approx lt/ 0.4. Near x /approximately/ O the Cu/sup 2 +/ atoms in the CuO/sub 2/ layers form a simple Neel lattice, and there is no ordering of the nonmagnetic Cu/sup 1 +/ atoms in the ''chain'' sites. With increasing oxygen content some of the Cu/sup 1 +/ atoms are converted to Cu/sup 2 +/, which leads to frustration of the interplanar coupling and eventually to a second type of ordering. Very recently, large single crystals of YBa/sub 2/Cu/sub 3/O/sub 6+x/ have been grown, making possible inelastic scattering studies of magnetic excitations. Spin waves within the CuO/sub 2/ planes are observed to have a velocity /approx gt/ 0.5 eV /angstrom/. 26 refs., 6 figs.
Research Organization:
Brookhaven National Lab., Upton, NY (USA)
DOE Contract Number:
AC02-76CH00016
OSTI ID:
7192573
Report Number(s):
BNL-41521; CONF-880703-6; ON: DE88015854
Country of Publication:
United States
Language:
English