Katsuaki Yanagiuchi

Quantitative evaluation of magnetic flux density in a magnetic recording head and pseudo soft underlayer by electron holography

The magnetic interaction between the pole tip of a single-pole head and a pseudo soft underlayer in perpendicular magnetic recording was observed by electron holography. The magnetic flux density inside the soft underlayer was quantitatively evaluated. The distribution of magnetic flux density was calculated using the finite element method, and the influences of the modulation of the reference wave and stray fields were investigated by comparison with experimental results. The flux density observed was found to be underestimated due to the modulation of the phase shift in reference wave. The magnetic flux measured experimentally was larger than that inside the specimen because of the relatively large stray fields above and below the specimen in the direction of the electron beam.

Elemental Distribution in Multilayer Systems by Laser-Assisted Atom Probe Tomography with Various Analysis Directions.

Elemental distributions in a magnetic multilayer system with the structure Si substrate/Ta/NiFe/Ru/CoFeB/Ru/NiFe were studied using atom probe tomography (APT) along different analysis directions. The distributions of Ru and B atoms, which require a high evaporation field, were strongly influenced by the APT analysis direction. In particular, B in the CoFeB layer appeared near the interface with the lower Ru layer when the analysis was anti-parallel to the film growth direction, while B atoms were observed at the other side of the CoFeB layer when the analysis was parallel to the film growth direction. Moreover, when the analysis was perpendicular to the film growth direction, a homogenous distribution of B atoms was found within the CoFeB layer. Owing to this B behavior, the underlying Ru layer was affected in both of these analysis directions. In APT measurements of such a multilayer system composed of a stack of different evaporation field materials, evaluation of the elemental distribution around interfaces should be performed from more than one analysis direction.

Observation of Magnetization Distribution in Soft Underlayer of Perpendicular Magnetic Recording Media by Electron Holography

The magnetic properties of the soft underlayer (SUL) of perpendicular recording media affect the recording performance significantly. We visualized and quantified the distribution and magnitude of magnetic flux in the recording layer and SULs of perpendicular recording media by electron holography. Pseudo-SULs with different permeability were deposited on the slider of perpendicular recording heads. The SUL with higher permeability produced higher write magnetic flux (By) as compared to the SUL with lower permeability, which results higher overwrite performance. Further, the magnitude profile of Bx in the SUL thickness direction was different for the two SULs; the magnitude of magnetic flux in SUL is related to the occurrence of adjacent track erasure.