Interfacial spin effects on Hex in metallic polycrystalline exchange biased systems

Abstract

In this work, we show how the magnitude of the annealing field affects the antiferromagnetic (AF) spin structure in an exchange biased trilayer with two ferromagnetic layers with different thicknesses pinned by a single AF layer. The value of Hex is moderated by the interfacial spin structure, while the mean blocking temperature remains constant. We find a 24% increase in Hex when the setting field (Hset) used in the field cooling procedure is increased from 0.25to20kOe, while all other setting conditions are kept constant. We show that the reversal of the order in the AF gives the same mean blocking temperature, 442±2K, while the maximum value of Hex increases with Hset from 220to286Oe. The superposition of the variation of Hex with the degree of order of the AF reveals the dependence of the blocking temperature TB on the bulk of the AF, while the magnitude of the exchange field is shown to be dependent not only on the order in the AF but also on the degree of alignment of the interfacial spins determined by Hset. A further confirmation that this is an interfacial effect comes from an observation that similar behavior occurs at both AF interfaces in our trilayer system.