Exchange biased CoFeB-MgO tunnel junctions at the onset of perpendicular anisotropy with in-plane/out-of-plane sensing capabilities

We investigate the transport properties of exchange biased CoFeB-MgO tunnel junctions at the onset of perpendicular anisotropy of the CoFeB free layer. Angular dependent measurements of the tunnel conductance (varying the applied magnetic field from the in-plane to the out-of-plane direction) show linear and hysteresis-free switching under low applied magnetic fields, demonstrating a new concept for a reversible in-plane/out-of-plane magnetoresistive sensor. State-of-the-art sensitivities were achieved, and a value of 0.4% TMR/Oe is observed in the direction perpendicular to the tunnel junction plane. An analysis of the anisotropy energies at play is performed based on a Stoner--Wohlfarth like model.

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