High-remanence square-loop Fe-Ni and Fe-Mn magnetic alloys

This paper describes the magnetic properties of Fe-rich, Fe-Ni and Fe-Mn binary alloys processed to exhibit high remanence and square hysteresis loops. Recrystallization and decomposition of the cold worked alloys within the low temperature (α+γ) two-phase region lead to an extremely fine but essentially isotropic microstructure with an average particle dia. of 2000-4000 Å. A subsequent wire drawing results in an elongated and aligned fine-scale two-phase (α+α\´) structure with an average calculated particle diameter of several hundred angstroms and a length-to-dia, aspect ratio of 100-300. The Fe-Ni alloys exhibit much lower coercive forces compared with the Fe-Mn alloys, which is attributed to the smaller difference in magnetic saturation moment between the two decomposed phases in the Fe-Ni alloys. An Fe-8 wt% Mn alloy gives magnetic properties ( G, , and Oe) comparable to or better than those of the high-cobalt Remendur or Nibcolloy alloys currently used in the remanent reed switches but contains no strategic element such as cobalt, and is very ductile for easy metallurgical processing. The Fe-Mn alloys with higher Mn contents exhibit a potential as permanent magnet alloys.