Fabrication of fully epitaxial magnetic tunnel junctions using L21-ordered Co2FeAl0.5Si0.5 electrodes and their tunneling magnetoresistance characteristics

Magnetic tunnel junctions (MTJs) using L21-ordered full-Heusler Co2FeAl0.5Si0.5 (CFAS) electrodes and an MgO tunnel barrier were prepared on MgO-buffered MgO (001) substrates by sputtering method. In situ and ex situ structural characterization confirms that the stacking structure of CFAS/MgO/CFAS is fully epitaxial, with smooth interfaces throughout. The microfabricated MTJs exhibited relatively high tunnel magnetoresistance ratios of 150% at room temperature and 312% at 7 K. We observed a symmetrical crossover point from the bias voltage dependence of differential conductance between parallel and antiparallel magnetization configurations, and also a flat behavior in the parallel conductance, which can be explained by considering the characteristic half-metallic band structure of L2(1)-ordered CFAS near the Fermi level. (C) 2008 American Institute of Physics.