Dependence of exchange coupling direction on cooling-field strength

Abstract

We studied the dependence of exchange coupling on cooling-field strength in an exchange-biased spin valve with a synthetic antiferromagnetic layer by experiment and theory. Our theory calculates magnetic anisotropy energies in each magnetic layer composing the spin valve during the field-cooling process, finds the minimum state of total energy, and explains how the magnetizations in the layers interact with one another during field-cooling under various cooling-field strengths. Calculations based on the theory well match results of the experimental measurements. Our observation shows that one has to carefully choose the cooling-field strength optimal for designing exchange-biased spin devices having a synthetic antiferromagnetic layer; otherwise the exchange coupling direction can significantly deviate from the cooling-field direction, which impairs performance.