Ta/NiFe/FeMn thin films with enhanced exchange bias prepared at room temperature by rotational deposition

Ta(20 nm)/NiFe(5 nm)/FeMn(20 nm) films were deposited on glass substrates by rotational deposition at room temperature. A significant enhancement in the exchange bias field (Heb) associated with very low coercivity (Hc) was achieved for the samples prepared at rotational speed (Rrpm) of 1 rpm. The Heb and Hc of the samples with Rrpm = 1 rpm were approximately double and smaller than half of those deposited by conventional continuous sputtering, respectively. Structural studies reveal that the rotational deposition not only improves the crystallization of FeMn but also facilitates the development of (111) texture through a preferred Ta(200) orientation. The sputtering powers of the constituent layers: WTa, WNiFe and WFeMn significantly affected the magnetic properties. Remarkable exchange bias properties, such as Heb of 26.67 kA/m and Hc of 1.99 kA/m were achieved at Rrpm = 1 rpm, WTa = 40 W, WNiFe = 70 W and WFeMn = 140 W. The Heb value obtained with the Ta/NiFe/FeMn films is comparable to that with the commercialized NiFe/IrMn system with a similar layered structure and it is more than 3 times larger than that of the sample deposited with fixed substrate in this study. The intensity of the FeMn(111) peak and the Scherrer coherent length are proportional to the Heb, indicating that the exchange bias behavior of the sample was dominated by the stability of the antiferromagnetic spin structure. The rotational deposition method proposed in this study favors practical applications in terms of both production cost and performance of spintronic devices.