Tailoring-compensated ferrimagnetic state and anomalous Hall effect in quaternary Mn–Ru–V–Ga Heusler compounds

Abstract

Cubic Mn2Ru x Ga Heusler compound is a typical example of compensated ferrimagnet with attractive potential for high-density, ultrafast, and low-power spintronic applications. In the form of epitaxial thin films, Mn2Ru x Ga was shown to exhibit high spin polarization and high tunability of compensation temperature by freely varying the Ru content x over a broad range (0.3 < x < 1.0). Here, we systematically studied Mn-Ru-Ga-based polycrystalline bulk buttons prepared by arc melting and found that, in equilibrium bulk form, the cubic structure is unstable when x < 0.75. To overcome this limitation, we alloyed Mn-Ru-Ga with a fourth element V. By adjusting the content of V in the Mn2Ru0.75V y Ga and Mn2.25-y Ru0.75V y Ga quaternary systems, the magnetic compensation temperature was regulated. Compensation was achieved near 300 K which was confirmed by both the magnetic and anomalous Hall effect measurements. Analyses of the anomalous Hall effect scaling in quaternary Mn-Ru-V-Ga alloys revealed the dominant role of skew scattering, notably that contributed by the thermally excited phonons, in contrast to many other 3d ferromagnets and Heusler compounds. We further showed that the Ga antisites and V content can simultaneously control the residual resistivity ratio (RRR) as well as the relative phonon and defect contribution to the anomalous Hall effect a’’/a’ in Mn-Ru-V-Ga, leading to a scaling relation a’’/a’ ∝ RRR1.8.