The permanent magnet and its manufacturing method

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PROBLEM TO BE SOLVED : To provide a highly heat-resistant permanent magnet (especially, rare earth magnet) that suppresses a deterioration in a coercive force in a high temperature range of the permanent magnet without using rare Dy or the like.SOLUTION : A permanent magnet has a magnetic crystal grain that has a crystal grain of a tetragonal intermetallic compound (RFeB) of a rare earth element (R), Fe and B, and a covering layer directly covering a specific crystal plane that is a crystal plane of at least a part of the magnetic crystal grain. The covering layer comprises a crystalline body of a metal or metallic compound having a coefficient of thermal expansion that, if a specific coefficient of thermal expansion that is a coefficient of thermal expansion of the magnetic crystal grain at the specific crystal plane is negative, is more than the specific coefficient of thermal expansion and, if the specific coefficient of thermal expansion is positive, is less than the specific coefficient of thermal expansion. The covering layer restricts a change in a lattice constant of the magnetic crystal grain at the specific crystal plane with increasing temperature. This suppresses deterioration in an anisotropic magnetic field with increasing temperature and thus deterioration in a coercive force of the permanent magnet.