Alternating-current electrical properties of CaMnO3 below the Neel temperature

The alternating-current electrical properties of polycrystalline CaMnO3 wer e investigated by alternating current complex-impedance analysis, and the d ielectric properties were analyzed over the temperature and frequency range s of 10 to 130 K and 20 Hz to 1 MHz, respectively. Direct-current conductiv ity and the Seebeck coefficient as a function of temperature also were anal yzed, Below 120 K, a Debye-type dielectric relaxation peak was observed. Ex perimental results implied that the number of charge carriers, which were g enerated by Mn3+, were not sufficient to stabilize small polarons, although it induced lattice distortion by the Jahn-Teller effect. Therefore, the th ermal motion of Mn3+ between potential minimums produced by lattice distort ion in the orthorhombic structure were believed to be the source of dielect ric relaxation. The temperature dependence of conductivity of the grain int erior (sigma(gi)) below 120 K was believed to be due to variable rangehoppi ng conduction, where sigma(gi) approximate to exp(-T-1/4).