Motoyoshi Murakami

Magnetic properties and microcolumnar structure of a TbFeCo memory layer for high-density magneto-optical recording

The MsHc value of the TbFeCo magneto-optical medium was reported as a key factor in high-density recording. Microstructure control of the magnetic underlayer was identified as an effective method for increasing the value of MsHc. This article describes the relationship between the magnetic properties and microcolumnar structure, which depends on the growth process and sputtering conditions of the TbFeCo recording film and the layer structure. It has been found that the columnar structure of the film self grows under the low migration energy process without any magnetic underlayer. The process uses a target in-face type dc magnetron sputtering system with a low temperature substrate. The amount of sputtering gas was observed to play a dominant role in the self growth of the film. The coercivity Hc value increases by creating a microcolumnar structure, but the squareness ratio of the Kerr hysteresis loop of the film is reduced. And the perpendicular anisotropy constant Ku is decreased to less than 1×106 erg...

Effect of RE-TM underlayer on the microstructure of TbFeCo memory layer for high-density magneto-optical recording

A magneto-optical (MO) medium has been investigated as high-density data storage. This MO medium sputtered from an intermetallic compound alloy target has advantages for mass production. However, it may have some difficulties for advanced high-density recording due to the controllability of the magnetic properties. In order to use the mass-production advantages of this MO medium, the intrinsic magnetic properties of its film must be clarified. This paper investigates the relationship between MsHc and the magnetic underlayers, which are controlled by the films microstructure. It is found that the MsHc of the memory layer can be increased by controlling the first magnetic underlayer; furthermore, the arranged microcolumnar structure in the memory layer is also found to be closely related to the underlayer. As a result, as much as 1.8/spl times/10/sup 6/ erg/cm/sup 3/ MsHc can be obtained even by sputtering from an alloy target. Adopting this film for the memory layer in a domain wall displacement detection system is promising approach for high-density recording that features reliably written tiny marks.

Properties of microstructure on amorphous film of rare earth–transition metal alloy for ultrahigh density recording

Controlling the microstructure of amorphous rare earth–transition metal films via the sputtering process was found to be an effective way of controlling their magnetic properties for applications as magneto-optical storage media. This paper describes how the relationship between a TbFeCo film’s magnetic properties and its microcolumnar structure depends on the sputtering conditions. An enhancement of electric resistance value was observed for the devices with a constriction columnar width in the 5–20nm range. The measured electrical resistance was over 1.0×10−5Ωm in this case. It is believed that the change of electrical resistance on the thin film is due to fluctuations in the density on the arranged microstructure or constriction of current induced by scattering because the film structure contains impurities. These same impurities are believed to be associated with the restriction of the trapped domain wall’s mobility. Furthermore, we observed a significant resistance change subsequent to the applicatio...

Recording Tiny Marks on a Magneto-optical Medium with Micro-Columnar Structure

The MsHc value of TbFeCo magneto-optical (MO) film has been identified as a key factor in high-density recording. A particular microstructure formed in the magneto-optical memory layer due to the magnetic underlayer was found to be effective for increasing the MsHc value in 160 nm thick TbFeCo recording film. However, a thinner memory layer is required for high performance of productivityThis paper describes the relationship between magnetic properties and the micro-columnar structure, which depends on the thickness of the TbFeCo recording film and its layer structureIt has been found that a thickness of more than 100 nm in the memory layer produced by sputtering from an alloy target is needed for the DWDD method. And there is some difficulty in recording a tiny mark on the 50 nm thick memory layer in a multi-layer MO mediumHowever, the static magnetic properties of the memory layer are not altered by differences in thickness. As much as 1.8 ×106 erg/cm3 Ku can be obtained by sputtering a thickness of less than 80 nm from an alloy target, and it is possible to perform ultra-high density recording in an 80 nm thick memory layer with a mark length of less than 50 nmThese results suggest that control of the exchange coupling boundary between the layers in a multi-layer MO mediummakes it possible to record stable tiny marks.