Shin-etsu Chemical Co., Ltd.

Kazuyoshi Watanabe

Susumu Sakaguchi

Masahiro Ogihara

Toshihiko Ryuo

Norifumi Yoshida

Masaaki Iguchi

Masakatsu Honshima

Hideaki Kikuchi

Yoshio Yamanaka

Toshihiko Ryuoh

Ken Itoh

Shinji Makigawa

An improvement in the Czochralski single crystal growing of a rare earth-gallium garnet such as gadolinium gallium garnet according to which the single crystal boules of a relatively large diameter and outstandingly free from any crystal defects and inclusions are readily obtained. The improved method comprises keeping the melt of the oxide mixture formed in an iridium crucible for at least 15 hours in the molten state before crystal growing is started. It was also shown that addition of certain additive gases, e.g. water vapor, carbon dioxide and oxygen, to the gaseous atmosphere mainly composed of, for example, nitrogen, in which crystal growing was performed, in a limited proportion was effective to further improve the crystal quality and to decrease the particulate inclusions in the single crystal boules.

Single crystal growing of rare earth-gallium garnet

In the crystal growing of GGG (gadolinium gallium garnet) by the Czochralski technique from a melt of the oxide mixture of gadolinium and gallium, zinc is added to the oxide melt as a dopant element in a limited amount so that the danger of crack formation in the grown single crystals can be greatly decreased contributing to the improvement of the productivity. Moreover, the GGG single crystal grown with zinc doping has remarkably reduced light absorption in the wavelength region of around 300 nm responsible to the yellowish tint of the crystals.

Method for the preparation of single crystals of gadolinium gallium

Permanent magnets are disclosed having a very high coercive force and a very great maximum energy product, and consisting essentially of a rare earth-cobalt based alloy. The alloy is expressed by the formula Sm.sub.1.sub.-u Ce.sub.u (Co.sub.1.sub.-v.sub.-w.sub.-x Cu.sub.v Fe.sub.w Mn.sub.x).sub.z where 0.ltoreq.u.ltoreq.0.20, 0.08.ltoreq.v.ltoreq.0.20, 0.ltoreq.w.ltoreq.0.08, 0.01.ltoreq.x.ltoreq.0.15 and 6.0.ltoreq.z.ltoreq.7.8, preferably 7.2.ltoreq.z.ltoreq.7.8. By using these alloys, the magnetic properties of the resultant permanent magnets are superiorly affected, and the magnet-preparing process is rendered much simplified. This is also because the conventional heat aging step may be eliminated, particularly when the z value is within the preferred range.

Rare earth-containing permanent magnets

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Gunma, Japan

Kazuyoshi Watanabe