Half-Metallic Ferromagnetism in the Heusler Compound Co${}_2$FeSi revealed by Resistivity, Magnetoresistance, and Anomalous Hall Effect measurements

Abstract

We present electrical transport data for single-crystalline Co${}_2$FeSi which provide clear-cut evidence that this Heusler compound is truly a half-metallic ferromagnet, i.e. it possesses perfect spin-polarization. More specifically, the temperature dependence of $\rho$ is governed by electron scattering off magnons which are thermally excited over a sizeable gap $\Delta \approx 100K$ ($\sim 9meV$) separating the electronic majority states at the Fermi level from the unoccupied minority states. As a consequence, electron-magnon scattering is only relevant at $T\gtrsim \Delta$ but freezes out at lower temperatures, i.e., the spin-polarization of the electrons at the Fermi level remains practically perfect for $T\lesssim \Delta$. The gapped magnon population has a decisive influence on the magnetoresistance and the anomalous Hall effect (AHE): i) The magnetoresistance changes its sign at $T\sim 100K$, ii) the anomalous Hall coefficient is strongly temperature dependent at $T\gtrsim 100K$ and compatible with Berry phase related and/or side-jump electronic deflection, whereas it is practically temperature-independent at lower temperatures.

References in corpus (1)

• Half-metallic ferromagnets: From band structure to many-body effects

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