Evidence of Fermi level control in a half-metallic Heusler compound ${\text{Co}}_{2}\text{MnSi}$ by Al-doping: Comparison of measurements with first-principles calculations

Evidence of Fermi level control in a half-metallic Heusler compound ${Co}_{2} MnSi$ by Al-doping: Comparison of measurements with first-principles calculations

Y. Sakuraba, K. Takanashi, Y. Kota, T. Kubota, M. Oogane, A. Sakuma, and Y. Ando

Phys. Rev. B 81, 144422 – Published 22 April 2010

Abstract

The Fermi level $(E_{F})$ control of half-metallic Heusler alloy ${Co}_{2} MnSi$ by Al-doping was challenged in magnetic tunnel junctions with a ${Co}_{2} {MnAl}_{x} {Si}_{1 - x}$ (CMAS) electrode. The observed bias voltage dependence on tunneling conductance ( $G − V$ curves) clearly shows a shift in $E_{F}$ toward the center of the half-metallic gap with $x$ , which showed excellent agreement with our first-principles calculations. However, the ratio of tunnel magnetoresistance (TMR) at 10 K to that at room temperature does not exhibit a remarkable change with $x$ . The weak exchange energy at the CMAS interface may be the origin for the large temperature dependence of the TMR ratio.