Hall effect measurement has been used to detect the perpendicular and in-plane magnetization components simultaneously in a [Co/Pd]n multilayer thin film with strong magnetic anisotropy along the direction perpendicular to the film plane. The angle between the driving current direction and the in-plane projection of the applied magnetic field was varied to investigate the contribution of in-plane magnetization component to the measured Hall voltage. Hall voltage under the canted magnetic field revealed that the output is the superposition of the anomalous Hall effect (AHE) due to the perpendicular component of magnetization and the planar Hall effect (PHE) due to the in-plane magnetization component. Odd symmetry characteristics of AHE and even symmetry characteristics of PHE with respect to applied field have been applied to extract the Hall voltage contributed by the two different magnetization components from their combined characteristic. Anomalous Hall voltage from the perpendicular magnetization component exhibited an irreversible hysteresis loop while that from the in-plane magnetization component was found almost reversible with respect to applied magnetic field. The method was effective to evaluate the in-plane component of magnetization in an ultrathin film under the canted magnetic field.

A new method for evaluating magnetic interaction among the particles in perpendicular magnetic recording layers under canted magnetic field has been proposed using anomalous Hall effect (AHE) measurement and vibrating sample magnetometer (VSM) measurement. Initial curves and magnetic hysteresis loops were measured to determine ΔM, an evaluation index to estimate interaction using the relation as ΔM=Minit−0.5×(Mup+Mdown). The degree of interaction ΔM can be determined as a vector by combining the results obtained by VSM and AHE measurements. Distribution of vertices (DOV) of ΔM can be regarded as a degree of interaction in a particular direction. The DOV of ΔM in Co–Cr–Ta thin film extended along the in-plane direction and showed gradual convergence as the applied field direction canted toward the film plane. This can be an indication that the magnetic particles in the Co–Cr–Ta thin film tend to incline to the applied field direction individually. On the other hand, the DOV of ΔM in Co/Pt multilayered thin film extended along the perpendicular direction and the shape of the trajectory of ΔM remained unchanged though the applied field direction deviated widely from the normal direction. This may be due to the strong perpendicular anisotropy in the Co/Pt multilayered thin film.

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A new method for evaluating magnetic interactions among particles in the recording layer (RL) with a soft magnetic underlayer (SUL) in a double-layered perpendicular magnetic recording media has been demonstrated. Since the RL and SUL reveal Hall effect responses with different symmetries regarding the applied magnetic field, it is possible to not only detect the anomalous Hall voltage from the RL and the planar Hall voltage from SUL simultaneously, but also to extract and evaluate their properties individually. In order to evaluate the magnetic interparticle interactions in the RL, an evaluation index of the ΔV-plot, which corresponds to the ΔM-plot, estimated using a simple relation among the initial magnetization curve, the upper and lower branch of the major hysteresis loop, was introduced. The initial magnetization curve of Co–Cr–Ta RL in a Co–Cr–Ta(100 nm)/Ni–Fe(50 nm) double-layered thin film, can be evaluated from the Hall voltage in positive and negative range of applied magnetic field using the point symmetry of the anomalous Hall voltage revealed by the RL. The negative peak in the ΔV-plot of the double layer indicated the dominance of magnetostatic interaction in the Co–Cr–Ta layer. Measurements under the canted applied field revealed field direction dependence in the estimated ΔV-plot. Adjustment of the driving current direction with respect to the in-plane projection of the applied magnetic field was found to be effective for selective rejection of the contribution from the SUL to the total Hall effect signal.

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