Thickness dependence of planar Hall resistance and field sensitivity in NiO(30 nm)/NiFe( t) bilayers

Abstract

We measured the planar Hall resistance (PHR) profiles in NiO (30 nm)/NiFe( t) bilayers for t=5, 10, 20 and 30 nm and analyzed its field sensitivity in terms of exchange-coupling field and anisotropy constant. The measured PHR shows linear field dependence at near H=0 as well as small hysteresis. The linear field range Δ H and resistance change, Δ R= R ∥− R ⊥, decrease with the NiFe thickness, where Δ H is calculated to be proportional to the anisotropy constant K u and exchange-coupling field H ex. However, the field sensitivity Δ R/Δ H shows a maximum value at t=20 nm; where K u is the minimum. The PHR has the advantage of a linear response at the operating field range and can be used for a recording read-out head and related applications.