公开(公告)号：JPH02256203A

公开(公告)日：1990-10-17

申请号：JP28316489

申请日：1989-11-01

Applicant: BASF AG

Inventor： MIHIYAERU BUORUFUGANGU MIYURAA ,  ETSUKEHARUTO SHIYUBUAPU ,  HERUMUUTO AUBUETAA ,  RAINAA FUEZAA ,  RUDEI REENERUTO ,  NORUBERUTO MIYURAA ,  MANFUREETO OORINGAA

IPC: C01G49/00 ,  C01G37/027 ,  C09D5/23 ,  C09D7/12 ,  G11B5/706 ,  H01F1/11

Abstract: PURPOSE: To obtain needle-like ferromagnetic chromium dioxide material showing high coercive force field strength and a high saturation magnetization value by a method wherein water-containing chrome acid chrome III is heated up to the temperature of 200 to 500 deg.C in a high pressure reactor, and immediately after reaction to this temperature, the material is cooled down and the pressure of the high pressure reactor is relaxed. CONSTITUTION: Hydrous chrome acid chrome III, having the degree of hydration n of at leas 13 in the form of Cr2 (CrO4 )3 .nH2 O is decomposed at the temperature of 200 to 500 deg.C under the pressure of 50 to 700var. To be more precise, the hydrous chrome acid chrome III is heated up to 200 to 500 deg.C in a high pressure reactor, and after said temperature is attained, the material is cooled down immediately and the pressure of the reactor is relaxed. Accordingly, in the needle-like ferromagnetic material consisting of iron-containing chromium dioxide and containing the indium smaller than 2ppm and the cobalt smaller than 50ppm as the component of chromium dioxide, upon measurement in a magnetic field of 380kA/m, a ferromagnetic material, having a coercive field intensity higher than 61kA/m, can be obtained when a magnetizing operation of 70nTm /g or higher is conducted.