The Lorentz Parameter in Magnetic Fields in Dilute silver–Manganese Alloys at Helium Temperatures

Abstract

IN a recent attempt¹ to separate the lattice and the electronic components of the thermal conductivity of polycrystalline rods of dilute silver–manganese alloys at liquid helium temperatures, the method of Gruneisen–De Haas² was used. The measured thermal conductivities λ_[H] in magnetic fields (including H = 0), at a temperature T, were plotted against σ_[H] T (where the σ_[H]'S were the corresponding electrical conductivities at that temperature). If it can be assumed that the lattice thermal conductivity (λ_g) and the electronic Lorentz parameter (L_e) are unaffected by magnetic fields, the following relation should hold: The isotherms were indeed found to be approximate straight lines, from which it appeared that L_e is not significantly affected by magnetic fields. This method of analysis simultaneously brought out the result that (except probably at temperatures less than about 1° K.) L_e, in these alloys in zero field, violated the law of Wiedmann–Franz–Lorentz in that: (1) it had a value less than the normal ‘Sommerfeld’ value L_n; (2) it was not constant with respect to temperature, even in the liquid helium region.