Quasireversible magnetoresistance in exchange-spring tunnel junctions

We report a large, quasireversible tunnel magnetoresistance in exchange-biased ferromagnetic semiconductor tunnel junctions wherein a soft ferromagnetic semiconductor (Ga1-xMnxAs) is exchange coupled to a hard ferromagnetic metal (MnAs). Our observations are consistent with the formation of a region of inhomogeneous magnetization (an "exchange spring") within the biased Ga1-xMnxAs layer. The distinctive tunneling anisotropic magnetoresistance of Ga1-xMnxAs produces a pronounced sensitivity of the magnetoresistance to the state of the exchange spring.