Inverse magnetoresistance in chromium-dioxide-based magnetic tunnel junctions

Magnetic tunnel junctions have been fabricated using half-metallic chromium-dioxide (CrO2) epitaxial film with a Co counterelectrode. The native insulating layer formed on the surface of CrO2 after air exposure is used as the tunneling barrier. These junctions exhibit nonlinear current-voltage characteristics, and the changes in junction resistance with applied field correspond to the coercivities of the two magnetic layers. The maximum observed magnetoresistance (MR) is about 8% at 4.2 K and has a negative sign, i.e., the resistance of the junction with parallel alignment of the electrodes is higher than with antiparallel alignment. This is opposite of what is normally observed with transition-metal electrodes and an Al2O3 barrier. Possible reasons for the inverse MR are discussed based on previous results on manganite/Co junctions. © 2001 American Institute of Physics.