Electron Structure and Optical Properties of the Mn1.8Co1.2Al Alloy and Spin Gapless Semiconductor State

Abstract

This paper studies the optical properties of the Mn_1.8Co_1.2Al alloy, whose composition is close to that of spin gapless Mn₂CoAl semiconductor. Our investigation found the absence of intraband absorption contribution, which is an anomalous behavior of optical properties of the alloy. The presence of intense interband absorption in the IR range of spectrum indicates the existence of low-energy gap in the band spectrum of the alloy, which was found by electron structure calculations of the Mn_1.75Co_1.25Al alloy.