Thermal stability of magnetic characteristics in Tb40(FeCoV)60 films

Films with a composition of Tb40(FeCoV)60 were fabricated by dc magnetron cosputtering from a multiple target arrangement at different substrate temperatures. The samples before and after annealing have been investigated by magnetic force microscope, vibrating sample magnetometer and other testing means for their structure and performance. With the increase of substrate temperature (Ts), out-of-plane coercivity decreases to a minimal value at Ts = 150 °C and then increases rapidly while saturation magnetization reaches their highest value at a moderate substrate temperature of 150 °C. A homogenous high-contract stripe domain and a low-contrast island domain are obtained for the samples prepared at 150 °C and at 250 °C, respectively. High substrate temperature stabilizes the films against subsequent annealing which tends to eliminate the anisotropy. The coercivity decreases with increasing annealing temperature (TA), but which shows hardly relaxation until the TA reaches the original Ts. The easy direction of magnetization can be turned from perpendicular to in-plane direction at high annealing temperatures which increase with substrate temperature.

► A minimum μ0Hc (⊥) and a maximum Ms are obtained at Ts = 150 °C before annealing. ► Stripe and island domain are obtained at Ts < 250 °C and at Ts = 250 °C respectively. ► Annealing can relax anisotropy and can turn easy direction of magnetization. ► Films show hardly relaxation of μ0Hc until TA reaches the original Ts.