Hitachi Metals, Ltd.

501 Hitachi Metals, Ltd.

Minoru Endoh

Masaaki Tokunaga

Shigeho Tanigawa

Katsunori Iwasaki

Yasuto Nozawa

Hiroshi Kogure

Tsutomu Nakamura

Setsuo Ando

Noriaki Meguro

Koichi Oda

Toru Fukushi

An R-T-B magnet (R is at least one kind of rare-earth elements including Y, and T is Fe or Fe and Co) has an electrolytic copper-plating film where the ratio [I(200)/I(111)] of the X-ray diffraction peak intensity I(200) from the (200) plane to the X-ray diffraction peak intensity I(111) from the (111) plane is 0.1-0.45 in the X-ray diffraction by CuKal rays. This electrolytic copper-plating film is formed by an electrolytic copper-plating method using an electrolytic copper-plating solution which contains 20-150 g/L of copper sulphate and 30-250 g/L of chelating agent and contains no agent for reducing copper ions and has a pH adjusted to 10.5-13.5.

Electrolytic copper-plated R-T-B magnet and plating method thereof

Magnet assemblies for installation into a voice coil motor is described. A pair of magnetic pieces are molded into circular arc shapes of different radii and positioned concentrically across a gap. The ends of such the pair of magnet pieces, are joined to a similarly-molded other pair of magnet pieces. The direction of magnetization of the former pair of magnet pieces is reverse that of latter pair of a magnet pieces. On the upper curved surface of each of the two units of lower magnet pieces of smaller radius, a cut plane, for example, is formed in order to provide unbalanced cubic volume between one half and the other half from the center plane of a magnet piece, thus increasing the gap magnetic flux density being generated inside the gap at the sections of larger cubic volume, thereby improving overall evenness of the gap magnetic flux density distribution.

Magnet assembly and a voice coil motor using such magnet assembly

A permanent magnet having good thermal stability, consisting essentially of the composition represented by the general formula:

Permanent magnet with good thermal stability

A the magnetically anisotropic magnetic powder having an average particle size of 1-1000 .mu.m and made from a magnetically anisotropic R-TM-B-Ga or R-TM-B-Ga-M alloy having an average crystal grain size of 0.01-0.5 .mu.m, wherein R represents one or more rare earth elements including Y, TM represents Fe which may be partially substituted by Co, B boron, Ga gallium, and M one or more elements selected from the group consisting of Nb, W, V, Ta, Mo, Si, Al, Zr, Hf, P, C and Zn. This is useful for anisotropic resin-bonded magnet with high magnetic properties.

Anisotropic magnetic powder and magnet thereof and method of producing

A process for manufacturing a rare earth-iron-boron alloy permanent magnet by, after sintering, keeping the sintered alloy at temperatures of 750.degree.-1000.degree. C. for 0.2-5 hours, slowly cooling it at a cooling rate of 0.3.degree.-5.degree. C./min. to temperatures between room temperature and 600.degree. C.; annealing it at temperatures of 550.degree.-700.degree. C. for 0.2-3 hours, and rapidly cooling it at a cooling rate of 20.degree.-400.degree. C./min. The permanent magnet contains a matrix, a B-rich phase and a Nd-rich phase. In grain boundaries of the matrix phases covered by bcc phases, thin, fine plates of the bcc phases projecting into the matrix phases are once increased by the first heat treatment and slow cooling and then eliminated by the annealing.

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Kumagaya, Japan

Minoru Endoh