Rare earth-iron magnet powder and its manufacturing method

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PROBLEM TO BE SOLVED : To provide a rare-earth-iron-based magnet powder for a bond magnet, which is superior in the moldability of a composition prepared from the powder for the bond magnet, and in mechanical strength of the bond magnet, and to provide a production method therefor. SOLUTION : The rare-earth-iron-based magnet powder has a film containing Fe, P, O and RE (RE is a rare earth element) with a film thickness of 100 nm or less on its surface. The amount of Fe which exists in the film in a metallic state is 2.0% or less when the amount is determined by measuring Fe2p3/2spectrum on the surface of the magnet powder with an X-ray photoelectron spectroscopy apparatus and then calculating the amount based on the area of the obtained spectrum profile. The film is formed by bringing the magnet powder into contact with a treatment liquid containing phosphoric acid, and then heating and drying the wet film at a particular temperature. The amount of Fe in the metallic state is reduced by the operation of repeating the treatment of contacting phosphoric acid and the heating and drying treatment. COPYRIGHT : (C)2011, JPO&INPIT