Interface and Surface Effects on Domain Wall Depinning Fields

We study the impacts of interfaces and thin film surfaces on magnetic domain wall depinning field, velocity as well as other magnetic properties by controlling the aluminum oxide thickness on the perpendicularly magnetized Pt/Co/AlO_x heterostructures. It is observed that the maximum values of coercivity and depinning field and minimum domain wall velocity for the 5 nm ALO_x thickness at room temperature. We adopted the low-temperature magneto-resistive transport measurement to investigate CoO_x content at the Co/AlO_x interface and atomic force microscopy images are used for the quantification surface roughness of all samples. The wide range of variation of the coercive field at the lowest possible temperature of 25 k is observed and the 5 nm aluminum oxide thickness sample’s coercivity lies very close to the mean value of all samples revealing the significant variation of CoO_x content at the interface. In addition, We found a very small dependence of RMS values of surface roughness with the AlO_x thickness which is also consistent with the depinning field variation trend at room temperature. Our work is helpful to design magnetic heterostructures by controlling the depinning field and other magnetic characteristics applicable in the field of low-power next-generation data storage devices.