The effect of Fe and Ru substitution for Ni on the thermopower in MgCNi_3

TL;DR

This study investigates how substituting Fe and Ru for Ni in MgCNi3 affects its thermopower, revealing changes in carrier type and the influence of magnetic moments, with implications for understanding its electronic properties.

Contribution

It provides new thermopower data on MgCNi3 with Fe and Ru doping, highlighting carrier type changes and the negligible effect of magnetic moments on thermopower.

Findings

Thermopower is negative in MgCNi3, indicating electron carriers.

Substitution increases the absolute value of thermopower and can change its sign.

Magnetic moments of Fe do not significantly affect thermopower.

Abstract

The intermetallic perovskite MgCNi3 is a superconductor with a Tc=7 K. Substitution of Fe and Ru for Ni decreases Tc monotonically as the doping concentration is increased. Here we report thermopower measurements, S(T), on MgCNi3, MgCNi3-xFex and MgCNi3-xRux. For MgCNi3, the thermopower is negative, - 12.5 mikroV/K, at 300 K. The absolute value of S decreases as x increases in MgCNi3-xFex and MgCNi3-xRux. The sign of S changes from negative to positive at low temperatures for values of x > 0.01. These data show that the carriers in MgCNi3 are electrons, and by increasing x and decreasing temperature, the participation of hole carriers clearly increases. The influence of the magnetic moments of the Fe atoms on the thermopower is not visible.