MAGNETIC-STRUCTURE IN FERH FROM CONSTRAINED TOTAL-ENERGY CALCULATIONS

The volume dependence of antiferromagnetic and ferromagnetic total-energy solutions derived from constrained total-energy band calculations is shown to explain the pressure and magnetic field effects on the antiferromagnetic to ferromagnetic transition in FeRh. We show that zero-point energy corrections are necessary to obtain reasonable agreement with experimental critical pressures and magnetic fields, and that the difference in electronic specific heats of the different magnetic states is small and does not play a role in the transition. Lattice constants of the magnetic states are inverted with respect to Invar, leading to enhanced rather than invariant thermal expansion near the transition, so that FeRh can be classified as an "anti-Invar" system.