Composition and Magnetic Properties of Ni75MnxAl25-x Alloys (0 less than equivalent to x less than equivalent to 25). I. Paramagnetic Properties.

In the Ni-Mn-Al ternary system, solid and liquid alloys having a constant composition of 75 at. % Ni were investigated by magnetothermal analysis. The results of magnetic susceptibility measurements of Ni//7//5Mn//xAl//2//5//-//x alloys with the Mn concentration varying from 0 to 25 at. % in the temperature range of 300 to 1800 K were used to establish the vertical section of the Ni//3Al-Ni//3Mn partial phase diagram, which is in agreement with the one proposed by Masahashi et al. This phase diagram shows the existence of an ordered gamma prime phase region which extends from the Al-rich side at high temperatures to the Mn-rich side at low temperatures. The substitution of Mn atoms for Al in the intermetallic compound Ni//3Al, having a Ll//2 - type crystal structure, results in an increase in the magnetic susceptibility. Ni-Mn-Al ingot alloys with a Mn concentration greater than 3. 5 at. % show ferromagnetism at room temperature. The magnetic susceptibility of the Ni-Mn-Al alloys in the gamma region, as well as in the liquid region, obeys an extended Curie-Weiss law, and the manganese atoms probably have a 3d**6 configuration.