Magnetism and exchange in the layered antiferromagnet $NiPS_3$

Chandrasekharan, Nirmala and Vasudevan, Sukumaran (1994) Magnetism and exchange in the layered antiferromagnet $NiPS_3$. In: Journal of Physics: Condensed Matter, 6 (24). pp. 4569-4579.

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Abstract

The anisotropic susceptibility of the layered antifemomagnet $NiPS_3(T_N = 155 K)$ has been measured between 45 K and 650 K. The system may be described by the effective spin Hamiltonian $H = DS^2_{iz}-\sum_{ij} J_{ij}S_i . S_j$, with the quadratic single-ion anisotropy terms introducing anisotropy in an otherwise isotropic situation. The exchange I and single-ion anisotropy parameter D were determined from an analysis of the anistropic susceptibility data for two different models: (i) the Oguchi model, in which a pair of spins chosen at random is treated exactly while its interactions with the rest of the crystal are approximated by a mean field and (ii) the correlated effective field (CEF) approximation developed by Lines, which reduces the many-body problem to a single-particle, non-interacting ensemble form, by the introduction of static temperature-dependent correlation parameter, which are evduated by forcing consistency with the fluctuation-dissipation theorem. It is found that the CEF approximation is superior to the Ognchi model in describing the susceptibility of $NIPS_3$. The exchange and crystal field parameters for the CEF approximation are J / k = -58.0 K; D / k = 16.1 K; $g_l_l$ = 2.05 and $g_\perp =2.13$.

Item Type: Journal Article Copyright of this article belongs to Institute of Physics. Division of Chemical Sciences > Inorganic & Physical Chemistry 17 Oct 2006 19 Sep 2010 04:31 http://eprints.iisc.ernet.in/id/eprint/8260