Large Tunneling Magnetoresistance at Room Temperature Using a Heusler Alloy with the B2 Structure

A Co₂Cr_0.6Fe_0.4Al Heusler alloy film exhibited a B2 structure, which was deposited using a magnetron sputtering system on a thermally oxidized Si substrate at room temperature without any buffer layers. The film exhibited the magnetic moment of 2.04µ_B per formula unit, nearly the integer number of Bohr magnetons, suggesting a localized nature of ferromagnetism similar to that of many Heusler compounds, which is a necessary condition for half metallicity. A spin- valve-type tunneling junction with a Co₂(Cr, Fe)Al Heusler alloy film was fabricated using metal masks, which consists of Co₂Cr_0.6Fe_0.4Al(10 nm)/AlO_x (1.8 nm)/CoFe (3 nm)/NiFe (5 nm)/IrMn (15 nm)/Ta (5 nm), deposited on a thermally oxidized Si substrate without a buffer layer. The junction demonstrated large tunneling magnetoresistances of 16% at room temperature and 26.5% at 5 K.