Tailoring magnetic anisotropy in Tb-Fe-Co thin films by rapid thermal annealing

In this work, we explore the possibility of tailoring of magnetic anisotropy in Tb-Fe-Co thin films by rapid thermal annealing (RTA) of as-deposited films for various time intervals. Rapid thermal annealing of 200 nm thick Tb21Fe62Co17 was carried out at 550 °C under vacuum for different annealing times viz., 2, 5, 10, 15, 20 and 30 min. Transmission electron microscopy (TEM) studies indicated that the as-deposited films had an amorphous structure with fine nano-sized columnar morphology. Upon RTA nucleation of Fe-Co nano-crystals embedded in amorphous Tb-Fe-Co matrix could be evidenced. It was found that while the as-deposited films exhibited a strong perpendicular magnetic anisotropy, increasing annealing time resulted in an increasing in-plane magnetic anisotropy component and a decreasing perpendicular anisotropy component resulting in different tilted angle magnetic anisotropies. The decrease in PMA with increasing annealing time was also evidenced from the decrease in out-of-plane (OOP) coercivity and squareness ratio. With increasing annealing time, the PMA was found to decrease due to the nucleation of Fe-Co nano-crystalline phase which induces an in-plane magnetic anisotropy. The results of present study indicate that magnetic anisotropy either along the in-plane or OOP or tilted at the desired angle can be realized in a single magnetic layer by tuning the annealing time during RTA.