Magnetic Properties of Ultrathin TbFeCo Magnetic Films With Perpendicular Magnetic Anisotropy

In this study, we report on the experimental results of ultrathin TbFeCo films fabrications. The effects of annealing conditions on the magnetic characteristics of ultrathin TbFeCo magnetic films with various under- and capping-layers were explored. The effects of using SiNx, Al and Ti as capping- and under-layers are also investigated. We found that in contrast to the flat surface of SiN, the rugged interfaces induced by Al and Ti layers are beneficial in enhancing the perpendicular magnetic anisotropy for ultrathin TbFeCo films with thickness down to 3 nm. The STEM line scan shows the strong diffusion of Al atoms into TbFeCo layers. Annealing treatment can be used for control of coercivity from 85 Oe to 1 kOe.

I. Introduction

Recently, amorphous rare-earth-transition metal (RE-TM) films have been studied for spintronic applications because of their perpendicular magnetic anisotropy (PMA) and tunable magnetic properties [1]–[3]. In some applications, such as spin-transfer switching [2] the thickness of the RE-TM layer should be thin enough in order to reduce the critical writing currents, while maintaining suitable anisotropy for thermal stability. In addition to composition variation, another way to modify the magnetic properties of RE-TM thin films is by the addition of under- and/or overlayers, such as W [4] Al [5]–[7] Ag [7] [8] TiN [9] and AlN [10] which can provide oxidation protection and coercivity enhancement. In this study, we present the magnetic properties of ultrathin perpendicular TbFeCo magnetic layers of thicknesses 3 nm and an analysis of mechanism which supports the perpendicular anisotropy. The coercivities of ultrathin TbFeCo films can be controlled by suitable annealing treatment from 85 Oe to 1 kOe. Fig. 1.

Hysteresis loops for TbFeCo (6 nm) with various capping and under layers.