Hot pressed GdIG for magnetooptic memory application

Abstract

This paper describes the preparation of polycrystalline GdIG by hot pressing and reports the most relevant properties of the material. Hot pressed samples were prepared using various conditions of time (1 to 20 hours), temperature (900 to 1300°C), and pressure (300 to 1000 kg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). Dense specimens with grain diameter ranging from 1 to 10μm were prepared. Thin wafers made by sectioning and polishing samples have high coercive field (higher than 200 Oe), good hysteresis loop squareness ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Br/Bm = 0.85</tex> ), and high figure of merit ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2\beta/\alpha \sim 2</tex> ). These properties make them well suited for optical mass memory application. This was confirmed experimentally, and a bit density of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5 \times 10^{5}</tex> bit/cm <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was obtained by laser beam thermomagnetic writing.