Low temperature specific heat of Fe₆₅(Ni1 − xMnx)₃₅ alloys

Low temperature specific heat measurements were carried out for f.c.c. Fe 65 (Ni 1 − x Mn x ) 35 ternary alloys which cover the electron concentration range from 7.65 to 8.70. The electronic specific heat coefficient γ has a large peak against the mean electron concentration e / a around 8.5 and its peak value is 6.5 × 10 −3 cal/mol deg 2 . On the basis of the itinerant electron ferromagnetism this large γ‐value can be explained as purely electronic origin taking the change of exchange splitting of spin up and spin down bands into consideration, and the increase in γ in the Invar region has been shown to play an important role in the sharp deviation of the average magnetic moment from the Slater‐Pauling curve. An enhancement of the γ values similar to that found by Gupta et al. in f.c.c. Fe‐Ni and Fe‐Mn alloys was observed in these ternary alloys.