Thermomagnetic recording characteristics of amorphous Tb-Fe /(BiY)<inf>3</inf>(FeGa)<inf>5</inf>O<inf>12</inf>

Abstract

An amorphous Tb-Fe film of Fe-rich composition was directly overlayered to Bi substituted iron garnet films, (BiY) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (FeGa) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> and (BiYbSm) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (FeGa) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> to make a composite film for recording medium in thermomagnetic recording and magneto-optical read out system. In the optimum combination of a 1.2 μm thick Tb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">82</inf> film of 110 G in magnetization on a 0.85 μm thick (BiYbSm) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (FeGa) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> film, thermally recorded area as small as 1.5 μmφ in the former was exactly transcribed into the latter, and it still stayed stably under the magnetic field of 400 Oe with the opposite polarity. The reflectivity and poler Kerr rotation of the same film showed marked wavelength dependence accompanying large enhancement of polar Kerr rotation due to multiple reflection of incident light between the both interfaces, garnet film-GGG and garnet film-Tb-Fe film. Consequently, magneto-optical figure of merit was enhanced up to 1.2 deg. at λ=600 nm and 0.75 deg. at λ=700 nm which were ten and eight times larger than those of a Tb-Fe film, respectively.