Spin reorientation transition and its gas absorption effect on Ni/fct-Fe films at 110 K

Using the in-situ magneto-optical Kerr effect, we study the spin reorientation transitions (SRT) in Ni/fct-Fe films on Cu (001) at 110 K. Induced by the Ni capping, the out-of-plane easy axis of magnetization rotates to in plane because of the modification of the surface anisotropy with Ni atoms. We find that the Ni critical thickness, where the SRT happens, decreases linearly with increasing Fe film thickness. Similarly, the gas absorption also strongly affects the surface anisotropy and, thus, influences the Ni critical thickness. With further Ni capping, a second SRT happens, with the easy axis of magnetization rotating back to out of plane.