The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 30, 2001
Filed:
Oct. 13, 1998
Tsutomu Chou, Chiba, JP;
Masao Shigeta, Chiba, JP;
Masahiro Karatsu, Chiba, JP;
Mari Fujii, Chiba, JP;
Chikara Ishizaka, Chiba, JP;
Katsumi Saito, Chiba, JP;
Katsuhiko Wakayama, Ibaraki, JP;
Shohei Mimura, Kanagawa, JP;
Masahiro Ito, Kanagawa, JP;
Other;
Abstract
The invention is a magnetic recording medium which is effectively protected against forgery by the alteration of recorded data, and a method for carrying out writing and reading on this magnetic recording medium. The magnetic recording medium of the invention comprises a recording material composed of a crystalline alloy containing Fe and Al . In the recoding material, the total amount of Fe and Al is at least 90 at % and the atomic ratio Al/(Fe+Al) ranges from 0.30 to 0.45. The recording material changes from a disordered phase to an ordered phase by heating. The recording material has a saturation magnetization of at least 45 emu/g prior to heating and lowers its saturation magnetization by at least 35 emu/g upon heating. Dark regions are observable in a bright-field image of the recording material by transmission electron microscopy, the dark regions accounting for 15-60% of the recording material in areal ratio and having a maximum breadth of 10-200 nm.