1278.    GUILLAUD, C.  [Ferromagnetic Properties of the Compounds Manganese-Nickel Alloy and Cementite.]  Compt. Rend., vol. 219, 1944, pp. 614-616; Chem. Abs., vol. 40, 1946, p. 1711.

       Alloys of Mn with Ni containing 57-85 atomic % of Ni are paramagnetic when tempered and ferromagnetic when annealed.  The most strongly ferromagnetic alloy corresponds to the composition MnNi₃.  This was prepared by fusing pure Mn (99.98%) and pure Ni (99.76%) in an Al₂O₃ crucible in a high-frequency furnace.  To obtain the maximum magnetization the specimens were annealed for 3 wk. at approximately 470°.  At 480°, MnNi₃ is no longer ferromagnetic.  The change is not completely reversible, and the alloy is paramagnetic or weakly ferromagnetic depending on the speed of cooling to a temperature below 480°.  In the case of ferromagnetism the spontaneous magnetization reappears at 480°.  This indicates probably the simultaneous existence of a Curie point and a point of transformation.  Curves are given showing the specific magnetization as a function of T² and the law of approach to saturation at 290° K, and 0° K, as a function of the reciprocal of the internal field.  For 0° K., σω=98.16.  Curves are also given showing the results obtained on an exceptionally pure specimen of Fe₃C from which the value σω=169.3 at 0° K, is deduced.