Thermoelectric Power and Electrical Resistance of Chromium-Iron Alloys from 125° to 625°K

Abstract

The Seebeck coefficient S of alloys with up to 23 at. % iron has been measured from 125° to 625°K. S of alloys with 10, 15, 19, and 23 at. % Fe was nearly temperature-independent and had values between 6 and 9 μV/°K. Pure chromium and alloys with up to 4 at. % Fe had a nearly temperature-independent S at temperatures above 375°K, with S ranging from 13 to 16 μV/°K. However, S exhibited a pronounced maximum below room temperature. The maximum values and the corresponding temperatures are: pure chromium: 21 μV/°K, 275°K; 1 at. % Fe: 27 μV/°K, 240°K; 2 at. % Fe: 40 μV/°K, 175°K; 4 at. % Fe: 34 μV/°K, 280°K. The resistance anomaly of chromium rich samples with maxima below room temperature was similar to that found by other authors. This anomaly has been attributed to the transition to antiferromagnetism. It has been shown that the peak of the phonon drag term S (phon) in pure chromium occurs at 25°K. The observed peaks in our experiments above 125°K should be due to the electron-diffusion term S (diff). It can be deduced from S of alloys with 10 to 23 at. % Fe, that s-d scattering has only a small effect on the S (diff) and it is concluded that the structure change of the conduction band at the transition to antiferromagnetism is responsible for the maxima in S. The indicated energy dependence of the Fermi surface is in qualitative agreement with band models deduced from Hall-effect measurements in the same alloys.