Tailoring magnetic properties by tuning the interface in a Pt/Co/Pt/IrMn system with perpendicular and double-exchange biases

Abstract

We prepared Pt/Co/Pt(tPt)/IrMn heterostructures with perpendicular exchange bias by inserting a Pt spacer between Co and IrMn. X-ray diffraction (XRD) demonstrates that the IrMn and Pt layers exhibit a (111) texture promoting perpendicular exchange bias. Here, the samples for various Pt spacer thicknesses exhibit double-shifted hysteresis loops with the coexistence of positive and negative exchange biases. Magnetic force microscopy (MFM) measurement indicates that this behavior in the as-grown state results from the formation of an antiferromagnetic bidomain state with opposite signs. Also, the magnetic loop behaviors can be tailored by tuning the exchange bias, coercive and switching fields which are sensitive to sub-nanometer changes in the spacer layer (Pt) thickness. It is found that the optimum thickness of the Pt layer is 0.8 nm by considering a well-defined single remanence state, where HEB is about seven times as large as the coercivity. Our results indicate that large exchange bias and rather small coercivity necessary for the single-remanence state in the double-shifted Pt/Co/Pt/IrMn systems can be achieved by tuning the interface at atomic level. Moreover, magnetic properties were analyzed in detail depending on Pt space spacer layer thickness between Co and IrMn layers. These results may be useful for potential applications in future multilevel memory devices.