Massive Magnetic-Field-Induced Structural Transformation inGd5Ge4and the Nature of the Giant Magnetocaloric Effect

Abstract

A massive magnetic-field-induced structural transformation in ${\mathrm{G}\mathrm{d}}_5{\mathrm{G}\mathrm{e}}_4$, which occurs below 30 K, was imaged at the atomic level by uniquely coupling high-resolution x-ray powder diffraction with magnetic fields up to 35 kOe. In addition to uncovering the nature of the magnetic field induced structural transition, our data demonstrate that the giant magnetocaloric effect, observed in low magnetic fields, arises from the amplification of a conventional magnetic entropy-driven mechanism by the difference in the entropies of two phases, borne by the concomitant structural transformation.