Fluctuation Effects on the Physical Properties of Cd2Re2O7 Near 200 K
R. Jin, J. He, J.R. Thompson, M.F. Chisholm, B.C. Sales, D. Mandrus
Abstract
Experimental investigation of the resistivity \rho, susceptibility \chi, specific heat C_p, and Hall coefficient R_H of the pyrochlore Cd_2Re_2O_7 reveals the presence of a continuous phase transition of uncertain origin with critical temperature T* = 200 K. Electron and X-ray diffraction measurements indicate that a commensurate structural transformation accompanies the changes in the electronic properties, implying that lattice as well as electronic degrees of freedom are involved in the transition. Remarkable scaling relationships between \rho, \chi, and C_p are observed, indicating that fluctuations are crucial in the transition regime. Scenarios involving both spin and ionic density fluctuations are considered in the evaluation of the data. Although the observed structural transition suggests that ionic density fluctuations are likely to be important, a scaling relationship between \rho and \chi over a wide temperature range suggests that spin fluctuations may be playing a role as well.