Strong spin-lattice coupling in multiferroic HoMnO3:: Thermal expansion anomalies and pressure effect -: art. no. 060407

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