Sarbanoo Das

Simultaneous detection of perpendicular and in-plane magnetization component in a [Co/Pd]n perpendicular magnetic recording media

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 com...

Evaluation of magnetic interactions in a double-layered perpendicular magnetic recording media using ferromagnetic Hall effects

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 ...

Magnetic interaction among particles in Co–Cr–Ta media and Co/Pt multilayered media evaluated by anomalous Hall effect

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...

Magnetic interactions in FePt∕soft magnetic underlayer double-layered structure observed by anomalous Hall effect

The effect of magnetic interactions between an FePt recording layer with perpendicular magnetic anisotropy and a soft magnetic layer of FeCoB (or NiFe) was investigated using the anomalous Hall voltage measurement method. The nucleation field and the slope around the coercivity of the Hall hysteresis loop revealed by the recording layer were found to significantly decrease depending on the type of interface. The coercivity corresponding to the in-plane magnetization components of the soft magnetic layer was found to increase while coexisting with an FePt layer.

Effect of intermediate Layer at recording Layer/soft magnetic underlayer interface in perpendicular recording media observed by ferromagnetic Hall effect

Effect of the presence of a Pt intermediate layer (IL) between a 50-nm-thick CoCrPt recording layer (RL) and a 100-nm-thick NiFe soft magnetic under layer (SUL) has been studied using ferromagnetic Hall effect under the tilted magnetic field. CoCrPt RL with/without Pt IL between the RL and SUL revealed different inclination in the anomalous Hall voltage loop indicating the effect from the Ni-Fe SUL. Magnetic properties of the SUL, simultaneously detected from the Planar Hall voltage suggested the interaction effect between the CoCrPt RL and Ni-Fe SUL.

Evaluation of magnetic interaction in [Co/Pd]/sub n/ multilayered thin film for perpendicular magnetic recording media under the tilted magnetic field

In this paper, we propose a method of evaluating magnetic interactions among magnetic particles simultaneously along the perpendicular and in-plane direction in such media.

Detection and Analysis of the Shortest Bit Missing at High Data Rate Recording

Fast response in magnetic recording systems is a continuous demand as the data rate is increasing more rapidly than ever before. Recently, we observed the phenomena that several of the shortest bits are missing in random data patterns from patterns recorded on the magnetic media. This phenomenon is assumed to be caused by the shortest bits not being recorded properly because the write field rise time and transition energy are insufficient. To easily observe this phenomenon in experiments on our spinstand, we developed a method that is based on a comparison of different data patterns. In this paper, we analyze the shortest bits missing by using a spinstand and discuss the mechanism of these bits and a testing algorithm in order to contribute to designing a recording system for high data rate performance.

Recoiled particle irradiation effects to RE-TM films around compensation point observed by ferromagnetic Hall effect

The perpendicular magnetization characteristics of Gd/sub x/(Fe/sub 90/Co/sub 10/)/sub 1-x/ and Tb/sub x/(Fe/sub 90/Co/sub 10/)/sub 1-x/ around their compensation point was measured by the ferromagnetic Hall measurement since the Hall measurement has a sufficient sensitivity to observe magnetization characteristics of very thin films with low saturation magnetization. Gd/sub x/(Fe/sub 90/Co/sub 10/)/sub 1-x/ thin films were deposited by ion beam sputtering using either Ar or Kr gas to investigate the effects of recoiled particles. Ion irradiation effects were also investigated using dual ion beam sputtering technique.

Hall effect study of soft magnetic properties of thin films (FeCoB, NiFe) stacked on FePt thin films with perpendicular magnetic anisotropy

In this study we have investigated the magnetic properties of to the soft magnetic thin films, such as FeCoB or NiFe, deposited on [001] oriented FePt thin film with strong perpendicular magnetic anisotropy using the ferromagnetic Hall effect measurement.