Switchable voltage offset in a Heusler alloy-based magnetic tunnel junction

We investigate the tunneling magnetoresistance (TMR) of the magnetic tunnel junction (MTJ) comprised of the Heusler alloy (Co2MnSi) and the pinned CoFe to probe the spin polarization of Co2MnSi. From the TMR value thus obtained, we estimate 40% polarization of Co2MnSi, much less than 100% expected for the suspected half metal. Remarkably, upon applying the weak switching magnetic field to the MTJ in the parallel state, our system exhibits a finite open-circuit voltage on the order of several 10μV in the anti-parallel state. We have demonstrated that the reversal of magnetic dipolar field induced by the Heusler alloy as a free layer can generate an electromotive force of the same order and can clearly explain the observed polarity and sample size dependence of the voltage offset at zero bias current.