Magneto-Optical Properties of Multilayered FePt for High Density Recording
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J5.1.1
Magneto-Optical Properties of Multilayered FePt for High Density Recording Hojun Ryu, Dongwoo Suh, Yongwoo Park, Eunkyung Kim, Yonggoo Yoo, Woosug Jung, Mun Cheol Paek Basic Research Laboratory, Electronics and Telecommunication Research Institute 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea ABSTRACT The Si3N4/FePt/Si3N4/Al/Si structures have been fabricated. 57 nm silicon nitride films have been used as dielectric layer for heat dissipation and 500 nm Al film used for reflection layer. The Kerr rotation angle was changed with the FePt layer thickness. At the 65 % Pt composition in 10 nm FePt layer, the maximum Kerr rotation angle was 0.82˚. As increase with FePt thickness the Kerr angle is slightly decreased. The change of Kerr rotation angle and the thermal behavior of multilayered structure according to FePt thickness variation were also calculated by computer simulation. INTRODUCTION The FePt thin film with L10 phase is very widely studied for its large magneto-optical Kerr effect and high anisotropy field. These properties of FePt thin film is suitable for the one of good candidate material of high density recording. It had been reported that the magnetic anisotropy and magneto-optical Kerr rotation of FePt are known to correlate with the degree of chemical ordering and the magnetic anisotropy energy Ku [1]. To obtain good reading/writing characteristics at the short wavelength, the material shoul have the large polar Kerr rotation angle in order to reduce noise level. The FePt thin film has been shown good magneto-optical Kerr effect for high density magneto-optical recording media[2]. In this paper we investigated the potential for magneto-optical recording with fabrication of the Si3N4/FePt/Si3N4/Al/Si multilayered structure. Therefore we present the effect of the FePt thickness for magneto-optical Kerr effect and the thermal behavior of this multilayered structure. EXPERIMENTAL DETAILS
J5.1.2
We have fabricated the multilayer thin film by sputtering method. All layers have been sputtered in argon pressure of 5x10-3 torr. We adopted co-sputtering method of Fe and Pt targets to obtain the various compositions of FePt thin films. We have controlled the applied rf-powers level of each targets for tuning the Fe or Pt composition. The Al layer was deposited up to 500 nm at 300 watts dc-power as an optical reflection layer. The dielectric layer which sandwiches the FePt layer was deposited at 200 watts rf-power for adjusting 405 nm wavelength measurement. When the laser beam is irradiated at the recording layer through the transparent substrate, the reflection is occurred by Al layer. For reducing the interference effect by the reflection beam, the dielectric layers should have the thickness for destructive interference. Hence we set to 57 nm thickness of dielectric layer which was derived from the following equation. Ddielectric = λ ( 4 ⋅ ndielectric )
where, Ddielectric is for the thickness of Si3N4, λ is for the wavelength and the ndielectric is for the refractive index of Si3N4. The refract
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