Magnetic tunnel junctions are fabricated by laser molecular-beam epitaxy employing a room temperature ferromagnetic semiconductor Ti1-x Cox O2-δ and a ferromagnetic metal Fe0.1 Co0.9 as electrodes and an AlOx tunnel barrier. The thickness of the AlOx barrier is systematically varied on a substrate during the growth by stencil mask. The junction resistance increases with the barrier thickness exponentially. The differential conductance and the tunneling magnetoresistance are significantly asymmetric with respect to bias voltage at low temperature, possibly due to the asymmetric junction structure and/or the degraded interface of AlOx Fe0.1 Co0.9.
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