Highly spin-polarized tunneling in fully epitaxial Co_2Cr_(0.6)Fe_(0.4)Al/MgO/Co_(50)Fe_(50) magnetic tunnel junctions with exchange biasing

摘要

Fully epitaxial magnetic tunnel junctions (MTJs) with exchange biasing were fabricated with a full-Heusler alloy CO_2Cr_(0.6)Fe_(0.4)Al (CCFA) thin film and a MgO tunnel barrier, where a Co_(50)Fe_(50) upper electrode was used in a synthetic ferrimagnetic Co_(50)Fe_(50)/Ru/Co_(90)Fe_(10) trilayer exchange-biased with an IrMn layer through the Co_(90)Fe_(10)/IrMn interface. The fabricated MTJs exhibited clear exchange-biased tunnel magnetoresistance (TMR) characteristics with high TMR ratios of 109% at room temperature and 317% at 4.2 K. A high tunneling spin polarization of 0.88 at 4.2 K was estimated for epitaxial CCFA films with the B2 structure.