PREPARATION AND PROPERTIES OF MAGNETIC METAL POWDERS OBTAINED BY A BOROHYDRIDE REDUCTION PROCESS

Experimental data are presented on pairs of magnetic metal powders with different compositions and magnetic properties obtained by a borohydride method in the presence (type I powders) and absence (type M powders) of a magnetic field. The density of the chains is found to be 0.957 (equal to that of Kondorskii) for type I and 0.743 (the value corresponding to the closest packing of spheres) for type M. From the measured magnetic parameters of the metal powders, the constant of surface anisotropy and the shape coercivity are calculated. The application of surface-active substances the the preparation of the powders causes no change in the type of the chains formed. The crystallization of the powders, which contain considerable amounts of boron and hydrogen, leads to the appearance of magnetocrystalline anisotropy and a change in the coefficient of surface anisotropy, which becomes negative. © 1990.