  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.
