Fumiya Ohmi

Cobalt‐titanium substituted barium ferrite films for magneto‐optical memory

We have studied Faraday rotation and magnetic properties of Co‐Ti substituted barium ferrite films with perpendicular anisotropy, which were prepared by targets‐facing‐type sputtering method on (111) oriented GGG substrates. Faraday rotation (θF) of 500–830 nm was measured by using the Faraday modulation method. It was found that θF increased proportionally to the content of cobalt in the wavelength range 700–830 nm. In the BaFe10.42Co0.78Ti0.8O19 film, Faraday rotation and magnetic properties were as follows: θF=0.75 deg/μm at 780 nm, anisotropy field: Hk=5.2 kOe, coercive force: Hc=800 Oe, Curie temperature: TC=380 °C. Thermomagnetic recording was achieved on this film by using a 780‐nm laser diode. As a result, 2.0‐μm bit patterns were observed by Faraday effect.

Magneto-optical properties and thermomagnetic recording of M-type Ba-ferrites

Abstract Thermomagnetic recording by Ar laser was achieved on a Ba-ferrite perpendicular film. The Faraday rotation of a Co-Ti substituted Ba-ferrite single crystal was 0.83° / μm at λ = 0.78 μm .

Ba-Ferrite Magneto-optical Recording Media

We have studied on the application of Ba-ferrite(BaFe12O19) to magneto-optical recording. It was found that CoTi substituted Ba-ferrite(BaCoxTixFe12-2xO19) films on GGG single crystals had Faraday rotation of 0.9deg/ µ m(λ=780nm) and Curie temperature of 320°C at X=0.9. And CoTi substituted Ba-ferrite films with the perpendicular magnetic anisotropy were obtained on glass substrate by using (111) orientated NiZn-ferrite(NixZn1-xFe2O4) films for under layer. From these results, Ba-ferrite magneto-optical recording medium which constitution is glass substrate, NiZn-ferrite under layer, CoTi substituted Ba-ferrite magnetic layer and stripe-shaped metal reflective layer for the guide tracks, is proposed from the optimization of each layer.

The preparation of Co-Ti substituted Ba-ferrite films

Abstract Co-Ti substituted Ba-ferrite (BaCo x Ti x Fe 12-2 x O 19 ; x =0, 0.75, 1.0) films have been deposited by a sputtering method on GGG single crystals with (111) orientation and on (111) oriented polycrystalline NiZn-ferrite films. The films deposited on both substrates had a polycrystalline structure with a magnetoplumbite phase (M phase). They exhibited c -axis orientation perpendicular to the film plane above the substrate temperature threshold ( T cry ) at which the crystallization of Ba-ferrite films occurs. T cry ) increased from 520°C ( x =0) to 650°C ( x =1.0) proportionally to the content of Co-Ti substitution. The Δθ 50 of the (008) plane of Co-Ti substituted Ba-ferrite films deposited on GGG single crystals was about 3.0° and about 2.5° for the simple Ba-ferrite films. On the other hand, the degree of c -axis orientation of Ba-ferrite films deposited on NiZn-ferrite films strongly depended on the (111) orientation of the NiZn-ferrite films. The Δθ 50 of the (008) plane of Co-Ti substituted Ba-ferrite films deposited on NiZn-ferrite films was about 4.5°.