Specific Heat of Dilute Alloys of the Transition Metals in Nickel

Abstract

The specific heat of nickel-based dilute alloys with the metals of the three transition series have been measured in the 1.2-10-K range with a precision of 0.1%. The electronic-specific-heat coefficient increases per unit impurity concentration at infinite dilution (in mJ/${\mathrm{K}}^2$ mole per unit atomic concentration) are $\frac{d\gamma }{\mathrm{dc}}{|}_0=18, 30, 43, -13\mathrm{}$ for Ti, V, Cr, Mn, respectively (first series). For the second series, we found 35, 48, 40, - 1.5, 2.5 for Nb, Mo, Ru, Rh, and Pd. For the third series (Ta, W, Re, Os, Ir, and Pt) the results are 34, 44, 54, 69, 29, and 14. In the three series, a strong $\gamma$ increase is to be noticed when the virtual bound state repelled by the impurity potential from the majority-spin band $d\uparrow$ crosses the Fermi level. However, the agreement with the present state of the theory is only qualitative; it was found that when the virtual bound state sits at the Fermi level, the $\frac{d\gamma }{\mathrm{dc}}{|}_0$ values are much higher than expected. They remain important when the virtual bound state is well above the Fermi level, the expected value being zero in this case. The same qualitative agreement and quantitative discrepancies between theory and experiment also arise for nonmagnetic impurities in non-transition-metal matrices.