Role of spin-glass-like interfaces in exchange-biased MnN/Fe thin films grown on W buffer layers

Abstract

This study reports the growth and investigation of (001)-oriented MnN/Fe thin films on the W buffer layer, focusing on detailed exchange bias (EB) studies, including thermal evolution (300–10 K) and the training effect. At room temperature, the magnetically annealed α-W/MnN/Fe/Ta stack exhibits an EB field (HEB) of 118 Oe. With decreasing temperature, particularly below 100 K, both HEB and coercive field (HC) show substantial increases, with HEB displaying a more pronounced enhancement. Analysis of the temperature-dependent HEB and HC data reveals an exponential trend, indicative of a spin-glass-like interface in the MnN/Fe system. At 10 K, the pronounced EB is accompanied by an asymmetric “kinked” magnetization reversal, suggesting a transition from uniaxial to biaxial anisotropy below 50 K due to spin-glass-like magnetic frustration at the interdiffused MnN/Fe interface. Training effect measurements further support the spin-glass-like MnN/Fe interface, with two distinct training mechanisms observed at 10 K: “athermal” and “thermal.” Finally, the spin-glass model demonstrates an excellent fit for the training effect data, validating the presence of spin-glass-like disorder at the MnN/Fe interface.