Half-metallic electronic structure of Co2MnSi electrodes in fully epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions investigated by tunneling spectroscopy (invited)

Abstract

We used tunneling spectroscopy to examine the spin-dependent electronic structure of Co2MnSi (CMS) electrodes facing a MgO barrier and the key tunneling mechanism in fully epitaxial CMS/MgO/CMS magnetic tunnel junctions (MTJs) that showed high tunnel magnetoresistance ratios up to 182% at room temperature and 705% at 4.2 K. Consequently, we developed a model of the spin-dependent electronic structure for CMS electrodes and a tunneling model that can consistently explain the observed tunneling spectra. Here, we show that lower (upper) CMS electrodes possess a half-metal gap of 0.40 eV (0.32 eV) with the Fermi level (EF) near the middle of the half-metal gap for both lower and upper CMS electrodes. Furthermore, we found strong evidence for the existence of interface states in the interfacial region of CMS electrodes facing a MgO barrier, as well as evidence of residual states in the bulk region of upper CMS electrodes, in both cases for minority spins around EF, and we show that interface states play a critical role for spin-dependent tunneling in these half-metallic CMS-based MTJs.