Dzyaloshinsky-Moriya antisymmetric exchange coupling in cuprates: Oxygen effects

Journal Article · Fri Jun 15 04:00:00 EDT 2007 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S106377610706009X· OSTI ID:21072461

We reconsider the conventional Moriya approach to the Dzyaloshinsky-Moriya antisymmetric exchange coupling for a single Cu{sub 1}-O-Cu{sub 2} bond in cuprates using a perturbation scheme that provides an optimal way to account for intra-atomic electron correlations, low-symmetry crystal field, and local spin-orbital contributions with a focus on the oxygen term. The Dzyaloshinsky vector and the corresponding weak ferromagnetic moment are shown to be a superposition of comparable and, sometimes, competing local Cu and O contributions. We predict the effect of oxygen staggered spin polarization in the antiferromagnetic edge-shared CuO{sub 2} chains due to the uncompensated oxygen Dzyaloshinsky vectors. The polarization is perpendicular to both the main chain antiferromagnetic vector and the CuO{sub 2} chain normal. The intermediate {sup 17}O NMR is shown to be an effective tool to inspect the effects of Dzyaloshinsky-Moriya coupling in an external magnetic field. In particular, we argue that the puzzling planar {sup 17}O Knight shift anomalies observed in the paramagnetic phase of the generic Dzyaloshinsky-Moriya antiferromagnetic cuprate La{sub 2}CuO{sub 4} can be assigned to the effect of the field-induced staggered magnetization. Finally, we revisit the effects of symmetric spin anisotropy, in particular, those directly induced by the Dzyaloshinsky-Moriya coupling. The perturbation scheme generalizes the well-known Moriya approach and presents a basis for reliable quantitative estimates for the symmetric partner of the Dzyaloshinsky-Moriya coupling. In contrast to the conventional standpoint, the parameters of the effective two-ion spin anisotropy are shown to incorporate the contributions of a single-ion anisotropy for two-hole configurations at both Cu and O sites.

• OSTI ID: 21072461
• Journal Information: Journal of Experimental and Theoretical Physics, Journal Name: Journal of Experimental and Theoretical Physics Journal Issue: 6 Vol. 104; ISSN JTPHES; ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANISOTROPY
ANTIFERROMAGNETISM
COPPER OXIDES
CRYSTAL FIELD
CUPRATES
ELECTRON CORRELATION
HOLES
KNIGHT SHIFT
LANTHANUM COMPOUNDS
MAGNETIC FIELDS
MAGNETIZATION
NUCLEAR MAGNETIC RESONANCE
OXYGEN 17
PARAMAGNETISM
PERTURBATION THEORY
POLARIZATION
SPIN
SPIN ORIENTATION
SYMMETRY