S. Uchiyama

Magnetization Process of Exchange-Coupled Ferrimagnetic Double-Layered Films

Magnetization curves are theoretically calculated for exchange-coupled ferrimagnetic double-layered (ECDL) films, each layer of which has a uniaxial anisotropy with the easy axis perpendicular to the film plane and exhibits a rectangular hysteresis loop. With this model are obtained the conditions for the appearance of anomalous and inverted hysteresis loops observed by the Kerr magneto-optic method. Experiments are made on Gd-Fe/Tb-Fe double-layered films deposited successively in a vacuum better than 10-6 Torr. By comparing the experimental switching field for the Gd-Fe layer in ECDL films with the theory, the energy density of the interface wall is estimated to be 1–2 erg/cm2.

Stress induced anisotropy in amorphous Gd-Fe and Tb-Fe sputtered films

The perpendicular anisotropy caused by the internal planar stress due to the substrate constraint in Gd‐Fe and Tb‐Fe sputtered films was investigated. The internal planar stress σ in these films is found to be very sensitive to preparation conditions, especially to the argon pressure during sputtering, PAr. Stress is compressive for low PAr and tensile for high PAr. The contribution of the stress to the total perpendicular anisotropy varies depending on PAr. Measurement of the anisotropy change before and after the removal of the substrate reveals that the predominant part of the perpendicular anisotropy originates from the internal stress due to the substrate constraint for Tb‐Fe films with a composition of around 30 at.%Tb, where the magnetostriction is extraordinarily large.

Performance of parallel stream type magnetic filter for HGMS

A new type of the HGMS filter is proposed in which the slurry flows parallel to the ferromagnetic fine wires (Parallel stream type magnetic filter). In this configuration, the capturing magnetic force scarcely competes with the drag force or the gravitational force. The recovery of the filter is calculated based on the particle trajectory model. The experimental result for hematite slurry agrees well with the present theory. A preliminary result is presented on the maintenance test of the filter recovery. This filter is expected to be easy to flush.

Magnetoelastic contribution to perpendicular anisotropy in amorphous Gd-Co and Gd-Fe films

The magnetoelastic contribution to the perpendicular anisotropy in rf sputtered amorphous Gd-Co and Gd-Fe films was investigated by the following three experiments: (1) Measurement of the magnetoelastic coupling energy, (2) measurement of the internal planar stress, and (3) the evaluation of the anisotropy due to the substrate constraint. In these experiments it was found that the magnetoelastic contribution to the perpendicular anisotropy is very sensitive to the preparation condition, especially to the substrate bias voltage V b during sputtering. The contribution of the magnetoelastic component to the perpendicular anisotropy is in an order of 104erg/cc, which corresponds to 10∼30% of the total perpendicular anisotropy.

Solubility and partial specific volumes of C60 and C70

Abstract The solubility and partial specific volumes (ν) of C 60 and C 70 in toluene and carbon disulfide solutions are investigated through precise measurements on the densities and the concentration dependence of the UV-vis absorption spectra. An anomalously large solubility (10.16 mg/ml) has been obtained for C 70 in carbon disulfide solution at 25°C. The results are interpreted within the framework of the preferential cluster (aggregate) formation of C 70 in solution. Furthermore, the obtained ν value gives an effective diameter of 10.42 A for C 60 which is in excellent agreement with the known van der Waals diameter of C 60 (10.34 A).

Giant Magnetoresistance in FeNiCo/Cu Multilayers

The giant magnetoresistance effect of Fe16Ni66Co18/Cu multilayers prepared by the RF magnetron sputtering method is reported. A magnetoresistance ratio as large as 35% is obtained at 300 K, and it oscillates as a function of Cu layer thickness. The oscillation period is about 1 nm, which is similar to the case of Co/Cu multilayers. The maximum interlayer coupling strength for the first peak is about 0.05 erg/cm2. For the second peak the coupling is as weak as 0.003 erg/cm2 with a magnetoresistance ratio of 13%.

Perpendicular Magnetic Anisotropy of TbCo Films

An experimental study has been made on the magnetic anisotropy of amorphous TbCo films prepared by rf co-sputtering. TbCo films prepared at a substrate bias voltage of –100 V exhibit a large uniaxial anisotropy of 2×106 erg/cm3 with its easy axis perpendicular to the film plane, whereas films prepared without the substrate bias exhibit the anisotropy with its easy axis in the film plane. The planar stress due to the substrate constraint considerably influences the perpendicular anisotropy through the large magnetostriction of about 2×10-4. When films with perpendicular anisotropy are removed from the substrate, the anisotropy energy decreases to 65–80 percent of its initial value. Annealing for one hour at 300°C destroys the perpendicular anisotropy almost completely.

Magneto-optical properties of PdCo based multilayered films

The magnetooptical and magnetic properties of multilayered films composed of PdCo alloy and other noble metal (Pd, Pt, or Cu) layers were investigated. Multilayered films were prepared by RF magnetron sputtering. Kerr rotation spectra (275-800 nm) of Pd/Co multilayered films resemble those of PdCo alloys. In the films composed of PdCo alloy and Pt bilayers, the Kerr rotation increases with increasing Pt content while the perpendicular anisotropy decreases. >

Magneto‐optic Kerr effect of amorphous Gd–Fe–Co films

Amorphous Gdx(Fe1−yCoy)1−x (0.25<x<0.28, 0<y<0.39) films have been prepared by coevaporation technique. The films exhibit the magnetization perpendicular to the film plane, and the Curie temperature rises with increasing Co content. The magneto‐optic polar Kerr rotation angel θk has been measured in the temperature range of 300–450 K. It is found that Co substituted films exhibit larger θk than Gd–Fe films in the wavelength range of 400–700 nm. The effect of Co substitution is very significant in high temperature range because of the high Curie temperature. The temperature dependence of θk can be fitted to magnetization of 3‐d transition metal sublattice using the mean field model, while the increase of θk at ambient temperature cannot be attributed to the rise of the Curie temperature.

Measurement of Anisotropy Dispersion by means of Ferromagnetic Resonance

It is reported that the magnitude dispersion and the angular dispersion of the anisotropy energy in permalloy films can be measured by means of the ferromagnetic absorption measurement at a radio frequency of about 0.5 Mc/s. Principles of the method for dispersion measurement are developed here on the basis of a particle domain model. The experimental setup as well as the results obtained are also shown.