Understanding the extraordinary magnetoelastic behavior in GdNi

Measurements as a function of both magnetic field and temperature along with first principles spin polarized calculations explain the remarkable magnetoelastic properties exhibited by GdNi below its Curie temperature. The lattice constants $a$ and $b$ elongate continuously by 0.35% and 0.49%, respectively, while the $c$ axis contracts by 0.78%, all without phase volume change. Calculations and experiment confirm a relatively shallow magnetization-dependent energy landscape modified by the increased spin splitting of the conduction band as the $4f$ moments order.