Junichi Sayama

Newly developed SmCo5 thin film with perpendicular magnetic anisotropy

A sputter-deposited SmCo5 thin film with perpendicular magnetic anisotropy has been developed. The Sm?Co film, composed of [Co (0.41?nm)/Sm (0.31?nm)]35, was prepared by sputtering on a Cu (100?nm)/glass substrate at various substrate temperatures. The coercivity was found to increase rapidly at 325?345?C and to be much greater in the direction perpendicular to the film surface than in the film plane. By using in-plane x-ray diffractometry, reflection peaks of the Sm?Co film deposited at 325?345?C were confirmed to originate from the SmCo5 phase, and the film showed a preferred orientation of the c-axis in the direction perpendicular to the film surface. The Co/Sm laminate structure deposited on the Cu seedlayer at an appropriate substrate temperature was found to be the key to promoting crystallization of the SmCo5 with its c-axis oriented perpendicular to the film surface.

Thin films of SmCo5 with very high perpendicular magnetic anisotropy

Thin films of SmCo5 with extraordinarily high perpendicular magnetic anisotropy were prepared by introducing a Cu∕Ti dual underlayer and controlling the substrate temperature during the sputter deposition. Under optimized conditions, the magnetic anisotropy constant reached 4.0×107erg∕cm3, and the coercivity and the remanence ratio in the direction perpendicular to the film surface were 12.0kOe and unity, respectively. The high perpendicular magnetic anisotropy is attributed to the high degree of preferred orientation of the c axis; the full width at half maximum in the rocking curve of SmCo5(002) reflection was 3.1°.

SmCo/sub 5/-based thin films with high magnetic anisotropy for perpendicular magnetic recording

An investigation was carried out on the effects of the addition of Cu and the thickness of the SmCo/sub 5/-based thin film with perpendicular magnetic anisotropy upon its magnetic properties, with the aim of reducing the Cu/Ti underlayer thickness. As a result, the Cu/Ti underlayer thickness necessary to obtain the squareness ratio of unity was successfully reduced from 125 to 50 nm. Moreover, for the SmCo/sub 5/ double-layered perpendicular magnetic recording media with a CoZrNb soft magnetic underlayer, the Cu/Ti underlayer thickness was further reduced to 35 nm. However, the magnetic cluster size and the values of coercivity and saturation field of the SmCo/sub 5/ media were found to be too large. Thus, we recognized the need for adjusting the cluster size and the magnetic properties to appropriate values, and also the need for investigating the possibility of using this material as patterned media or thermally assisted recording media.

Fabrication of SmCo Double-Layered Perpendicular Magnetic Recording Media

We fabricated SmCo5 double-layered perpendicular magnetic recording media with high perpendicular magnetic anisotropy for realizing ultra high density recording. A double-layered medium with a Ru buffer layer introduced between a Cu/Ti intermediate layer and a Co-Zr-Nb soft magnetic underlayer exhibited high perpendicular magnetic anisotropy, whereas that without the Ru buffer layer did not. Auger electron spectroscopy revealed that the Ru buffer layer inhibited interdiffusion between the Cu/Ti intermediate layer and the Co-Zr-Nb soft magnetic underlayer. We report here for the first time the read-write characteristics of SmCo5 double-layered perpendicular magnetic recording media. The medium noise was small in the medium with a Sm-Co layer deposited under high Ar gas pressure owing to small magnetic clusters

Reduction of medium noise of Co-Pd multilayered perpendicular magnetic recording media by a thin carbon interlayer

We report the effect of introducing a thin carbon interlayer to the recording layer on the read-write characteristics of Co-Pd multilayered perpendicular magnetic recording media. A 1-nm-thick carbon interlayer markedly reduced the medium noise and improved the output resolution, D/sub 50/. As a result, the signal-to-noise ratio at the recording density of 200 kFRPI for the medium was higher by 5 dB than that for the medium without the interlayer. We attribute these improvements in read-write characteristics to a decrease in the crystal grain diameter of the recording layer, resulting in suppression of the transition fluctuation of recorded bits. The Co-Pd multilayered perpendicular magnetic recording medium with carbon interlayer has a high thermal stability despite a slight degradation of perpendicular magnetic anisotropy.

Soft x-ray magnetic circular dichroism study of [Co/Pd] multilayered perpendicular magnetic films

The electronic and spin states of [Co/Pd] multilayered perpendicular magnetization films with various seedlayers have been investigated by means of soft x-ray absorption and magnetic circular dichroism spectroscopy at the Co L2,3-edges. The expectation values of the orbital angular momentum 〈Lz〉 and the spin angular momentum 〈Sz〉 of Co atom in the [Co/Pd] multilayered film were estimated using the sum rule. It was found that the seedlayer changes macroscopic magnetic properties of the [Co/Pd] multilayered film without affecting the electronic and spin states of the upper layers of Co.

Existence and origin of compensation layer thickness in Tb20Co80/Pd multilayered films

Magnetic properties of [Tb20Co80/Pd(0.8 nm)]20 multilayered films with a TbCo layer of thickness 0.2–8.0 nm were studied using spectroscopic techniques of soft x-ray absorption (XAS) and magnetic circular dichroism (MCD) at the Co L2,3 and Tb M4,5 edges. The compensation layer thickness of TbCo, where magnetization becomes zero, was observed to be 5–6 nm. XAS and MCD analyses using the sum rule revealed that the existence of the compensation layer thickness was primarily because the projected Tb 4f magnetic moment was enhanced with the increase in the layer thickness, while the Co 3d moment was independent of the layer thickness. Below the compensation layer thickness, Co sublattice magnetization was dominant.

Fabrication of SmCo

We fabricated SmCo5 double-layered perpendicular magnetic recording media with high perpendicular magnetic anisotropy for realizing ultra high density recording. A double-layered medium with a Ru buffer layer introduced between a Cu/Ti intermediate layer and a Co-Zr-Nb soft magnetic underlayer exhibited high perpendicular magnetic anisotropy, whereas that without the Ru buffer layer did not. Auger electron spectroscopy revealed that the Ru buffer layer inhibited interdiffusion between the Cu/Ti intermediate layer and the Co-Zr-Nb soft magnetic underlayer. We report here for the first time the read-write characteristics of SmCo5 double-layered perpendicular magnetic recording media. The medium noise was small in the medium with a Sm-Co layer deposited under high Ar gas pressure owing to small magnetic clusters

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We fabricated SmCo5 double-layered perpendicular magnetic recording media with high perpendicular magnetic anisotropy for realizing ultra high density recording. A double-layered medium with a Ru buffer layer introduced between a Cu/Ti intermediate layer and a Co-Zr-Nb soft magnetic underlayer exhibited high perpendicular magnetic anisotropy, whereas that without the Ru buffer layer did not. Auger electron spectroscopy revealed that the Ru buffer layer inhibited interdiffusion between the Cu/Ti intermediate layer and the Co-Zr-Nb soft magnetic underlayer. We report here for the first time the read-write characteristics of SmCo5 double-layered perpendicular magnetic recording media. The medium noise was small in the medium with a Sm-Co layer deposited under high Ar gas pressure owing to small magnetic clusters

Double-Layered Perpendicular Magnetic Recording Media

The soft x-ray absorption and magnetic circular dichroism spectra at the Co L2,3-edges of [Co/Pd]20 and [CoB/Pd]20 multilayered films, which were sputter-deposited in Ar gas containing N2 at room temperature, were measured to investigate the electronic and spin states of the films. The macroscopic magnetic properties, such as coercivity and saturation magnetization, and microstructural properties, such as grain size and preferred orientation, were markedly changed for the [Co/Pd]20 film by the B doping and N2 addition. The B doping and/or the addition of N2 gas caused appreciable changes not only in macroscopic magnetic properties but also in microscopic properties, such as the spin angular momentum and orbital angular momentum, throughout the multilayered film. On the other hand, a new spectral feature at the high energy side of the Co L3-edge peak in x-ray absorption spectra was found in only the films with N2 added. Thus, the microscopic properties, such as electronic and spin states, of the Co 3d electronic state for the [Co/Pd]20 and [CoB/Pd]20 films were changed by only the sputtering process with additive N2 gas.