Modified scaling of thermopower to heat capacity for Cr doped Kondo insulator FeSi near metal to insulator transition

Abstract

The Low temperature thermopower (S) and heat capacity (C) measurements are investigated for Cr doped FeSi. Metals having simple parabolic band structure whose entropy of free carriers used to scale as S/T proportional to γ, where γ is Sommerfeld coefficient leading to the validity of S/T to γ scaling. However, it is shown that the entropy of free carriers of metals derived from insulators violates such a scaling. Here, we have investigated the compositions which fall in the vicinity of (metal-to-insulator) critical concentration of Fe1-xCrxSi. These compositions are found to agree well with the modified scaling (nS/T vs γ) of thermopower to heat capacity by taking the carrier concentration n into consideration in the zero temperature limit. For higher concentrations of Cr, marked deviations from the scaling are observed probably due to the magnetic contribution such as Schottky effect to the heat capacity at low temperature.