Perminvar effects in some alnico magnets

Elements has shown that unusual magnetic properties resulted after suitable heat-treatment on Perminvar type alloys containing nickel-iron and cobalt. Slow cooling of such alloys through a narrow temperature resulted in their hysteresis loop being constricted in the second part of the quadrant. Recently Kaya has shown that constricted hysteresis loops also occur in Permalloys near Ni3Fe composition under conditions which promote limited order (short range). The quenched or well-annealed alloys showed normal loops. Such loops have so far been observed for soft magnetic materials only which can be magnetization normally proceeds through movement of domain boundaries. (Dr. Ved Prakash and Mr. C.R. Tewari, Scientists and Dr. B.R. Nijhawan, Director, National Metallurgical Laboratory, Jamshedpur)