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Strong spin-lattice coupling in multiferroic HoMnO3: Thermal expansion anomalies and pressure effect

C. dela Cruz, F. Yen, B. Lorenz, Y. Q. Wang, Y. Y. Sun, M. M. Gospodinov, C. W. Chu

cond-mat.str-elarXiv:cond-mat/0501615

Abstract

Evidence for a strong spin-lattice coupling in multiferroic HoMnO3 is derived from thermal expansion measurements along a- and c-axis. The magnetoelastic effect results in sizable anomalies of the thermal expansivities at the antiferromagnetic (TN) and the spin rotation (TSR) transition temperatures as well as in a negative c-axis expansivity below room temperature. The coupling between magnetic orders and dielectric properties below TN is explained by the lattice strain induced by the magnetoelastic effect. At TSR various physical quantities show discontinuities that are thermodynamically consistent with a first order phase transition.

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