A Model of the Electronic Structure of a FeRh Alloy Undergoing an Antferromagnetic–Ferromagnetic Phase Transition

Abstract

A new approach to describing the magnetic properties of FeRh alloys is proposed. It is based on two assumptions about the properties of 3d and 4d electrons in these alloys. The first is the assumption that the 4d band is submerged under the Fermi level to a depth that ensures its complete filling at a temperature T = 0 K. The second is the assumption that there are two different spatial distributions of 3d and 4d electrons that are compatible with one atomic structure. The first assumption makes it possible to explain the absence of uncompensated spins of 4d electrons in the low-temperature antiferromagnetic (AFM) phase of FeRh. The second assumption is proposed to explain the strong changes in the spin structure of the FeRh alloy upon the AFM–FM transition, while its atomic structure is almost unchanged. Attempts have been made to predict the new properties of the FeRh alloy that follow from these assumptions. Our second assumption proved to be successful and enabled us to predict the existence of local magnetic moments of 3d electrons in the AFM phase, which are larger than the magnetic moments of Fe ions. Measurements of the magnetic susceptibility of the FeRh alloy in the AFM phase confirmed this prediction.