ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Sputtered Ba ferrite films are promising media for magneto-optical (MO) recording because they have strong perpendicular magnetic anisotropy. However, MO activity of the Ba ferrites is low, which makes the feasibility as a practical medium poor. The MO activity is reported to be prominently enhanced by specific ions such as Bi3+, Co2+, and light rare earth ions in garnet ferrites, while, in Ba ferrites, the MO enhancement ions except Co2+ have not yet been known. We have recently found that Ni2+ substitution also enhances Faraday rotation in the visible region around hν=2.5 eV. In this paper we describe MO properties as well as microstructures of Ba1−xMxFe12−xNixO19 (M=La, Pr, x=0, 0.3, 0.6) films prepared by rf sputtering. The films were deposited on Gd3Ga5O12 (GGG) single crystal substrates at substrate temperature (Ts) of 400–600 °C by the conventional rf diode sputtering. When Ts≥550 °C for the incident rf power over 19 W/cm2, the films in situ crystallized in Ba–ferrite single phase. They had c-crystal axis well oriented normal to the film plane. The SEM and TEM observations revealed that the grain size in the films increases from several nm to ∼300 nm with increasing the incident power. The films with larger grains showed higher saturation magnetization and lower coercivity. Faraday rotation of the films was clearly enhanced in the visible around 2.5 eV with increasing Ni2+ substitution, though they showed rather complicated spectral structure inherent to the Ba ferrites. The enhancement factor of specific Faraday rotation at 2.5 eV was as large as 2×104 deg/x, independent of the kind of the rare earth ion substituted for Ba2+ for charge compensation. This implies that the substitution of the rare earth ion itself enhances no Faraday rotation in Ba ferrites. Thus, the MO enhancement around 2.5 eV may be attributed to the octahedrally coordinated Ni2+.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.352729
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