The critical specific heat of a glassy ferromagnet

Using standard ac calorimetry, we have measured the specific heat of the amorphous ferromagnet Fe75P15C10 in the neighborhood of its Curie temperature TC ≅ 600 K. Even though this material is structurally disordered, a sharp lambda-like cusp was observed, typical of a pure crystalline substance. We report the first determination of the critical specific heat exponent α = δ′ = -.18 ± .04 and the amplitude ratio A+/A- = 1.2 ± .3 for an amorphous ferromagnet and find that these values are typical of a Heisenberg system. Our results are in agreement with recent renormalization group calculations which indicate that the fixed point which characterizes the critical behavior will be stable against the addition of disorder to the ordered system if α < 0. © 1977.