Single-ion anisotropy, crystal-field effects, spin reorientation transitions, and spin waves in R{sub 2}CuO{sub 4} (R=Nd, Pr, and Sm)
- School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel)
- University of Maryland, College Park, Maryland 20742 (United States)
- Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396 (United States)
We report a detailed study of single-ion anisotropy and crystal-field effects in rare-earth cuprates R{sub 2}CuO{sub 4} (R=Nd, Pr, and Sm). It is found that most of the magnetic properties are mainly due to the coupling between the copper and rare-earth magnetic subsystem which exhibits a large single-ion anisotropy. This anisotropy prefers ordering of rare-earth moments along [100] for R=Pr and Nd and along [001] for R=Sm. Combined with a pseudodipolar interaction arising from the anisotropy of the R-Cu exchange, we can explain the magnetic structures of these materials. The spin reorientation transitions in Nd{sub 2}CuO{sub 4} can be explained in terms of a competition between various interplanar interactions which arises because of the rapid temperature dependence of the Nd moment below about 100 K. Finally we introduce a simple two-dimensional model for the Nd spin-wave spectrum. For zero wave vector, this model gives two optical modes involving Cu spins whose temperature-dependent energies agree with experimental results and an acoustic mode whose energy is predicted to be of order {radical}(2k{sub 4}{Delta}){approx}5{mu}eV, where k{sub 4} is the fourfold in-plane anisotropy constant and {Delta} is the Nd doublet splitting. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 531808
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 1 Vol. 56; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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