Spin-charge conversion in NiMnSb Heusler alloy films

TL;DR

This study demonstrates spin-charge conversion in NiMnSb Heusler alloy films via spin pumping from Y3Fe5O12, revealing temperature-dependent signals and interface-bulk contributions, advancing spintronic device engineering.

Contribution

It reports the first observation of spin-charge conversion in NiMnSb Heusler alloys, highlighting interface and bulk effects and their manipulation.

Findings

Unusual sign change of charge signal at low temperature

Two contributions to spin-charge conversion: interface and bulk

Manipulation of conversion via film thickness and structure

Abstract

Half-metallic Heusler alloys are attracting considerable attention because of their unique half-metallic band structures which exhibit high spin polarization and yield huge magnetoresistance ratios. Besides serving as ferromagnetic electrodes, Heusler alloys also have the potential to host spin-charge conversion which has been recently demonstrated in other ferromagnetic metals. Here, we report on the spin-charge conversion effect in the prototypical Heusler alloy NiMnSb. Spin currents were injected from Y3Fe5O12 into NiMnSb films by spin pumping, and then the spin currents were converted to charge currents via spin-orbit interactions. Interestingly, an unusual charge signal was observed with a sign change at low temperature, which can be manipulated by film thickness and ordering structure. It is found that the spin-charge conversion has two contributions. First, the interfacial contribution causes a negative voltage signal, which is almost constant versus temperature. The second contribution is temperature dependent because it is dominated by minority states due to thermally excited magnons in the bulk part of the film. This work provides a pathway for the manipulation of spin-charge conversion in ferromagnetic metals by interface-bulk engineering for spintronic devices.