Rotating-field magnetoresistance of exchange-biased spin valves

Abstract

We investigate the magnetoresistance (MR) of spin valves by (i) varying the strength of the field applied in a fixed direction and (ii) rotating the field with fixed strength. The latter data reflect in general a mixture of giant and anisotropic magnetoresistance (GMR and AMR). We present an experimental procedure to suppress the AMR contributions of all ferromagnetic layers in the spin valve without disturbing the GMR response. The resulting angular MR curves are fitted with a single-domain model to determine with high precision the exchange bias field, the uniaxial anisotropies, the GMR ratio, and the interlayer coupling field. The application of the method to differently prepared Ta͑5.0 nm͒ / NiFe͑3.0 nm͒ / FeMn͑15.5 nm͒ / NiFe͑3.0 nm͒ /Co͑2.0 nm͒ / Cu͑3.5 nm͒ /Co͑2.0 nm͒ / NiFe͑7.0 nm͒ spin valves with GMR ratios of 1.8% and 4% demonstrates the sensitivity and reveals differences of the order of a few percents of the exchange bias field for the uniaxial anisotropy fields of the free and pinned layer as well as for the interlayer coupling field.

Perpendicular Exchange-Biased Magnetotransport at the Vertical Heterointerfaces in La0.7Sr0.3MnO3:NiO Nanocomposites

“…The bias fields measured from R­(H) tests are determined by the average pinning field of the entire FM-AFM interfaces, while the values from M­(H) curves are dominated by the weakest site for the occurrence of nucleation during the magnetization reversal. , Hence the M­(H) technique measures the lowest limit of the actual H EB associated with the weakest pinned region, and thus gives much smaller values than those from R­(H) tests. In the material systems with uniform exchange coupling at the interface, the H EB values measured from M­(H) and R­(H) tests agree with each other, as observed in FeMn/NiFe exchange biased spin valves and high-quality CoO/Co and CoO/Fe bilayers . On the other hand, the discrepancy of H EB becomes significant in the presence of irreversible AFM domain formation and rearranged spin coupling, which strongly relates to the interface structure and geometry.…”

Misaligned anisotropies in spin-valve films studied through magnetoresistance and magnetization measurements

“…The angular variation of magnetoresistance at fixed magnetic fields of exchanged-bias SVs has been studied by many authors [31,32]. This technique is very useful for testing models and allows investigating magnetic anisotropies in SVs.…”

Electrochemical Preparation of Fe-Mn Alloy Film in Organic Bath.

“…FeMn is often used as the AFM layer in spin valves. FeMn requires an face centred cubic (FCC) seed layer, such as NiFe, Co or Cu, in order to crystallize the antiferromagnetic γ-FCC phase responsible for exchange bias [3][4][5][6][7].Fe-Mn alloys can undergo all of the three major types of martensitic transformations of Fe-based alloys, i.e. .…”