High tunnel magnetoresistance in fully epitaxial magnetic tunnel junctions with a full-Heusler alloy Co2Cr0.6Fe0.4Al thin film

Abstract

Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with a Co-based full-Heusler alloy Co2Cr0.6Fe0.4Al (CCFA) thin film, whose composition was close to the stoichiometric one, and a MgO tunnel barrier. Cross-sectional high-resolution transmission electron microscope observations indicated that all layers of the CCFA∕MgO∕Co50Fe50 MTJ layer structure were grown epitaxially and were single crystalline. The microfabricated CCFA∕MgO∕Co50Fe50 MTJs exhibited high tunnel magnetoresistance (TMR) ratios of 90% at room temperature and 240% at 4.2K. A high tunneling spin polarization of 0.79 at 4.2K was obtained for the epitaxial CCFA films from the TMR ratios.