Diffuson contribution to anomalous Hall effect in disordered Co2FeSi thin films

TL;DR

This study investigates how disorder affects the anomalous Hall effect in Co2FeSi thin films, revealing a dominant side-jump mechanism and a novel diffuson contribution, especially in amorphous films, with implications for understanding electron scattering processes.

Contribution

It uncovers a new diffuson-related contribution to anomalous Hall resistivity and longitudinal resistivity in disordered Co2FeSi films, highlighting the role of electron-diffuson scattering.

Findings

Side-jump mechanism dominates AHR regardless of disorder.

Diffuson scattering causes logarithmic temperature dependence in amorphous films.

AHR and resistivity minima arise from different scattering mechanisms.

Abstract

A wide variation in the disorder strength, as inferred from an order of magnitude variation in the longitudinal resistivity of Co2FeSi (CFS) Huesler alloy thin films of fixed (50 nm) thickness, has been achieved by growing these films on Si(111) substrates at substrate temperatures ranging from room temperature (RT) to 600 C. An in-depth study of the influence of disorder on anomalous Hall resistivity,longitudinal resistivity(LR) and magnetoresistance, enabled by this approach, reveals the following. The side-jump mechanism gives a dominant contribution to anomalous Hall resistivity (AHR) in the CFS thin films, regardless of the degree of disorder present. A new and novel contribution to both LR and AHR characterized by the logarithmic temperature dependence at temperatures below the minimum, exclusive to the amorphous CFS films, originates from the scattering of conduction electrons from the diffusive hydrodynamic modes associated with the longitudinal component of magnetization, called diffusons. In these amorphous CFS films, the electron-diffuson, e d, scattering and weak localization (WL) mechanisms compete with that arising from the inelastic electron magnon, e m, scattering to produce the minimum in longitudinal resistivity, whereas the minimum in AHR is caused by the competing contributions from the e d and e m scattering, as WL does not make any contribution to AHR. In sharp contrast, in crystalline films, enhanced electron electron Coulomb interaction (EEI), which is basically responsible for the resistivity minimum, makes no contribution to AHR with the result that AHR does not exhibit a minimum.