Effect of Ta underlayer on magnetic properties of FeMn/NiFe films

Abstract Effect of Ta underlayer on the magnetic properties of sputter-prepared NiFe(5 nm)/FeMn(20 nm) bilayer films have been studied. The magnetic properties of studied films are optimized by modification of working Ar pressure deposition of Ta (P Ta ) in the range of 2–12 mTorr and thickness of Ta (t Ta ) in the range of 0–25 nm. X-ray diffraction results show that the crystallinity of the FeMn(111) strongly depends on the P Ta and t Ta . All studied films exhibit smooth and flat surface with root-mean-square roughness below 1 nm due to deposition at RT. Large EB field (H eb ) of 65–123 Oe with small coercivity (H c ) of 5–16 Oe is obtained. Besides, the change of H eb with various P Ta and t Ta are related to the crystallinity of FeMn(111) layer, interfacial roughness, and also strain/stress. Correlation between magnetic properties and microstructure is also discussed. This study suggests that proper Ta underlayer is crucial in the exchange bias for NiFe/FeMn bilayer system.