Interface-induced enhancement of sensitivity in NiFe/Pt/IrMn-based planar hall sensors with nanoTesla resolution

Abstract

The planar Hall sensitivity of obliquely deposited NiFe(10)/Pt(t(pt)) /IrMn(8)/Pt(3) (nm) trilayer structures has been investigated by introducing interfacial modification and altering sensor geometry. The peak-to-peak PHE voltage and AMR ratio of the sensors exhibit an oscillatory increase as a function of Pt thickness up to 1 nm. This behaviour has been attributed to the strong electron spin-orbit scattering at the NiFe/Pt interface of the trilayers. The magnetic field resolution of 380 nT has been observed for the sensor with a spacer layer of 9 angstrom. The temperature-dependent PHE measurements indicate that the sensors continue to operate at 390 K with a sensitivity of 5.1 mu V/(Oe.mA). In order to further increase the sensitivity, the PHE sensors have been fabricated for a fixed Pt thickness of 8 angstrom by using the sensor architectures of a cross, tilted-cross, 1-ring, and 5-ring junctions. A sensitivity of 3.8 mu V(Oe.mA) has been obtained for the cross junction, while it considerably increased to 299 mu V/(Oe.mA) for 5-ring sensor geometry. The real-time voltage profile of the PHE sensors demonstrates that the sensor states are very stable under various magnetic fields and sensor output voltages turn back to their initial offset values. This provides a great potential for the NiFe/Pt/IrMn-based planar Hall sensors in many sensing applications. (C) 2019 Elsevier B.V. All rights reserved.