Magnetic and transport properties of Gd1−xCaxCrO3 (x=0.0–0.3): Effect of orbital degeneracy in thermoelectric power

Abstract

Detailed magnetic and transport properties of orthorhombic perovskites ceramics Gd1−xCaxCrO3 (x=0.0–0.3) have been reported. Magnetization measurements under both field cooled cooling (FCC) and field cooled heating (FCH) protocol reveal magnetization reversal at low temperature and low magnetic field. This indicates clear evidence of two magnetic sublattices aligned opposite to each other. The effect of Gd3+ ion on the low temperature magnetization decreases largely above x=0.2. The nature of temperature dependent dc magnetic susceptibility (χ) was Curie–Weiss like above the transition temperature (Tmax) with an effective magnetic moment (μeff) that decreased with the increase of Ca concentration. These orthochromites exhibit a temperature independent, large and positive thermoelectric power or Seebeck coefficient (S) value above 200K. Upon Ca2+ substitution, a concomitant decrease of the S value is found. The evolution of S as a function of hole concentration (Cr4+) can be well fitted by the modified Heikes formula taking into account the orbital degeneracy related to Cr3+ and Cr4+.