THIN DISK MAGNET WITH MICRO-CRYSTALLINE STRUCTURE

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The purpose of the present invention is to present a thin-plate magnet with a fine crystalline structure that is 70 mu m to 500 mu m thick, making miniature, thin magnetic circuits possible, and has, as cast, an inherent coercive force iHc of 2.5 kOe or higher and residual magnetic flux density of 9 kG or higher and a performance-to-cost ratio rivaling that of hard ferrite magnets when Nd-Fe-B fine crystalline permanent magnets with a low rare earth content that are a mixture of a soft magnetic phase and a hard magnetic phase are produced. iHc can be increased to 2.5 kOe or higher and the optimum roll circumferential speed range within which hard magnetic properties are realized can be expanded when compared to the conditions under which Nd-Fe-B ternary magnets are produce, while at the same time, a fine crystalline permanent magnet alloy with a thickness of 70 mu m to 500 mu m is obtained, by using an alloy melt with a specific composition to which Co, Cr, Mn, Ni, Cu, Ga, Ag, Pt, Au, or Pb has been added during the process whereby a fine crystalline permanent magnet alloy having a fine crystalline structure of 15 nm to 50 nm is produced directly from an alloy melt by continuously casting the alloy melt on a cooling roller that is rotating in an inert gas atmosphere under reduced pressure of 30 kPa or less.