Optimization of planar Hall effect sensor for magnetic bead detection using spin-valve NiFe/Cu/NiFe/IrMn structures

Abstract

Present paper deals with the planar Hall effect (PHE) of Ta(5 nm)/NiFe(tf)/Cu(1.2 nm)/NiFe(tp )/IrMn(15 nm)/Ta(5 nm) spin-valve structures. Experimental investigations are performed for 50 ?? 50 ?m2 junctions with various thicknesses of free and pinned layer tf 4, 8, 10, 15, 20 nm and tp 2, 3, 6, 8, 9, 12 nm. The results show that the thicker free layers, the higher PHE signal is obtained. In addition, the thicker pinned layers, the lower PHE signal. The highest PHE sensitivity S of 15.6 m??/Oe is obtained in the spinvalve configuration with tf 20 nm and tp 2 nm. This optimum structure is rather promising for micro magnetic bead detections. ?? 2009 IOP Publishing Ltd.