Large enhancement of sensitivity in NiFe/Pt/IrMn-based planar Hall sensors by modifying interface and sensor architecture

Abstract

The planar Hall sensitivity of obliquely deposited NiFe(10)/Pt(tPt) /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. This behaviour was attributed to the strong electron spin-orbit scattering at the NiFe/Pt interface of the trilayers. The temperature-dependent PHE signal profiles reveal that the Pt-inserted PHE sensors are stable even at 390 K with a high signal-to-noise ratio and an increased sensitivity due to reduction of exchange bias. In order to further increase the sensitivity, we have fabricated PHE sensors for a fixed Pt thickness of 8 {\AA} by using sensor architectures of a cross, tilted-cross, one-ring and five-ring junctions. We have obtained a sensitivity of 3.82 {\mu}V/Oe.mA for the cross junction, while it considerably increased to 298.5 {\mu}V/Oe.mA for five-ring sensor geometry. The real-time voltage profile of the PHE sensors demonstrate 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.