Sharp Angular Dependence of Free Layer Coercivity in Spin Valves with Ferromagnetic Interlayer Coupling

Abstract

The dependence of free layer coercivity on the angle between easy axis and applied magnetic field was studied on [Ta, (Ni80Fe20)60Cr40]/ Ni80Fe20/Co90Fe10/Cu/Co90Fe10/Mn75Ir25/Ta spin valves with various interlayer coupling. Sharp decrease on the angle was observed for ferromagnetically coupled spin valves. The coercivity was reduced down to tenth of Oersted without any decrease of GMR-effect by forming nearly parallel anisotropy configuration. The angles at which the transition from hysteretic to anhysteretic magnetic reversal takes place are detected by analyses of the angle dependence of coercivity. Interpretation of experimental data is based on Stoner-Wohlfarth coherent rotation approach.

Uniaxial anisotropy variations and the reduction of free layer coercivity in MnIr-based top spin valves

“…This has been revealed for macro-patterned spin valves with parallel anisotropy configuration, i.e., PDkEA [5,6]. Practical applications, however, need the micron-sized spin valves with the crossed magnetic anisotropy configuration.…”

“…In the case of the spin valves with parallel anisotropy configuration (PDkEA), the free layer coercivity decreases if an applied field deviates from PD, so that H c becomes equal to zero at angle H 0 [5,6]. To estimate H 0 for the annealed at 300 C sample (sample1) and unannealed one The GMR effect (empty circles), free layer coercivity (solid squares), and interlayer coupling field (empty squares) versus the annealing temperature (sample 2) with crossed anisotropy configuration, the magnetoresistance was measured at some fixed angles between the field and PD, H being changed from À2 to ?2 kOe.…”

“…4, 5) was interpreted in the framework of Stoner-Wohlfarth approach in [5,6] and [16]. Now let us consider the relationship between H 0 and H J =H A in the PD?EA configuration.…”

“…The formation of the crossed magnetic anisotropy configuration, when the angle between PD and EA is close to 90 , is the well-known way to decrease the free layer coercivity [4]. In [5,6], we have reported the reduction in the free layer coercivity by the deviation of applied magnetic field from PDkEA. Let H be an angle between a magnetic field H and PD and denote H 0 as the angle at which the magnetic reversal becomes anhysteretic.…”

“…Let H be an angle between a magnetic field H and PD and denote H 0 as the angle at which the magnetic reversal becomes anhysteretic. It has been shown in [5,6] that H 0 depends on the H J =H A ratio with H A being the free layer anisotropy field: the greater H J =H A , the less H 0 .…”