Review of the electronic specific heat of B. C. C. and F. C. C. solid solutions of first long period transition elements

A review will be given of the electronic specific heat vs. electron concentration for b. c. c. solid solutions, including new data for the systems V-Cr and Ti-V. The latter alloys show a maximum of γ at approximately 60 % V. The electronic specific heat coefficients correlate well will the superconductive transition temperatures, according to the Bardeen-Cooper-Schriffer theory, with an interaction coefficient V independent of composition. It was found that the CsCl-type ordered alloys in the ternary Ti Fe-TiCo and TiCo-TiNi systems possess electronic specific heat values paralleling those for the b. c. c. Cr-Fe alloys at the same average electron concentrations. The electronic specific heat values for the b. c. c. alloys of transition elements with one another can be apparently described to a surprising extent in terms of a more or less rigid band, the degree of filling up of this band with electrons being determined essentially by the average electron concentration for the alloy. This appears to hold even in cases where the electron concentration is determined by averaging over three different atomic species. As found also for the alloy VFe, with a CsCl-type ordered structure, ordering causes little, if any, change in the electronic specific heat values of these alloys. New low temperature specific heat measurements with f. c. c. solid solutions in the Mn-Fe, Mn-Ni, Fe-Ni, V-Ni systems gave coefficients for the specific heat term linear in temperature, which are in some cases quite inconsistent with each other if interpreted as electronic specific heat coefficients. Consistent γ values were obtained for simple ferromagnetic alloys and for non magnetic alloys. For alloys where the simultaneous presence of both ferromagnetic and antiferromagnetic interactions is known from magnetic measurements, or may be considered as very likely, the measured γ values are anomalously high. It has been proposed by Marshall (1) that a temperature-linear contribution to the low temperature specific heat can arise in instances where a sufficient number of spins are located in a near zero magnetic field. It appears from our results that this condition is often fulfilled in alloys having both ferromagnetic and antiferromagnetic interactions. As a result, in such cases the γ value measured at low temperatures comprises, in addition to the true electronic specific heat coefficient, also a magnetic component. Using only γ values obtained for simple ferromagnetic and for nonmagnetic alloys, the shape of the d-band for the f. c. c. solid solutions has been nevertheless successfully determined in the electron concentration range from approximately 8 to 10.