MAGNETIC POWDER AND ITS MANUFACTURE AND APPLICATION

WIPO Patent Application WO/1995/028718

A1

A magnetic powder which contains MnBi and has a mean particle diameter of 0.1-20 'mu'm. The coercive force is 3,000-15,000 Oe measured at 300 K in a magnetic field of 16 KOe and 50-1,000 Oe measured at 80 K in the same magnetic field. The magnetic susceptibility is 20-60 emu/g measured at 300 K in a magnetic field of 16 KOe. The rate of decrease of the magnetic susceptibility is below 40 % and the generated amount of metallic Bi satisfies the relation, metallic Bi/(MnBi + metallic Bi) < 0.5 (where metallic Bi represents the peak area from (012) face at the X-ray diffraction peak of Bi and MnBi represents the peak area from (101) face at the X-ray diffraction peak of the MnBi) when the magnetic powder is left as it is for seven days in an environment of 60 �C temperature and 90 % relative humidity. The magnetic powder has an excellent corrosion resistance and hardly deteriorates in saturation magnetization. Therefore, when a magnetic recording medium is manufactured by using this magnetic powder, falsification of records can be prevented.

KISHIMOTO MIKIO (JP)
KITAHATA SHINICHI (JP)
KANZAKI HISAO (JP)
OHTANI NORIAKI (JP)
SUEYOSHI TOSHINOBU (JP)

PCT/JP1995/000731

October 26, 1995

April 14, 1995

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HITACHI MAXELL (JP)
KISHIMOTO MIKIO (JP)
KITAHATA SHINICHI (JP)
KANZAKI HISAO (JP)
OHTANI NORIAKI (JP)
SUEYOSHI TOSHINOBU (JP)

G06K19/02; G11B5/706; G11B5/716; H01F1/047; H01F1/06; (IPC1-7): H01F1/06; G11B5/706

JPS5249500A	1977-04-20
JPS3517455B1
JPS5194804A	1976-08-19
US4617854A	1986-10-21
US4535809A	1985-08-20
JPS5433725A	1979-03-12
JPS5738962A	1982-03-03
JPS5738963A	1982-03-03
JPS5931764A	1984-02-20
JPS6057127A	1985-04-02
JPS6141048A	1986-02-27

See also references of EP 0706191A4

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