Weak itinerant ferromagnetism in Heusler type Fe2VAl0.95

TL;DR

This study investigates how slight chemical substitution in Fe2VAl transforms it from a non-magnetic semi-metal into an itinerant ferromagnet with low carrier density, revealing detailed magnetic, thermal, and transport properties.

Contribution

It demonstrates that 5% substitution of Al with Fe and V induces itinerant ferromagnetism in Fe2VAl, providing new insights into tuning magnetic states in Heusler compounds.

Findings

Fe2VAl0.95 exhibits ferromagnetism with TC = 33 K.

Magnetism is of itinerant nature with a small ordered moment.

Pressure decreases the Curie temperature at a rate of 0.061 GPa^-1.

Abstract

We report measurements of the magnetic, transport and thermal properties of the Heusler type compound Fe2VAl0.95. We show that while stoichiometric Fe2VAl is a non-magnetic semi-metal a 5% substitution on the Al-site with the 3d elements Fe and V atoms leads to a ferromagnetic ground state with a Curie temperature TC = 33+-3 K and a small ordered moment ms = 0.12 mB/Fe in Fe2VAl0.95. The reduced value of the ratio ms/mp = 0.08, where mp = 1.4 mB/Fe is the effective Curie-Weiss moment, together with the analysis of the magnetization data M(H,T), show magnetism is of itinerant nature. The specific heat shows an unusual temperature variation at low temperatures with an enhanced Sommerfeld coefficient, g = 12 mJK-2mol-1. The resistivity, r(T), is metallic and follows a power law behavior r(T) = r0+AT^n with n = 1.5 below TC. With applying pressure, TC decreases with the rate of (1/TC)(dTC /dP) = -0.061 GPa-1. We conclude substitution on the Al-site with Fe and V atoms results in itinerant ferromagnetism with a low carrier density.