Low temperature heat capacity and magnetic susceptibility of Ti3SiC2

In this paper, we report on the heat capacity and magnetic susceptibilities of bulk Ti3SiC2 samples in the 3-250-K temperature range. At 13.6 K, a nonmagnetic sharp anomaly of unknown origin, which disappeared when the sample was heated and quenched in water from 1400 degreesC, is observed. Curve fitting the c(p) data up to 100 K clearly shows that only four atoms-most likely one Si and three Ti atoms-of the six in a formula unit contribute to c(p) at the lowest temperatures. This reduces the Debye temperature theta(D) calculated from over 700 K to approximate to575 K. To obtain good agreement between experimental and calculated c(p) values in the 14<T<130 K temperature range, a theta(D) of 552 K and an optical mode with an Einstein temperature theta(E) of 219 K, which coincided with a soft shear mode observed in Raman spectroscopy, are assumed. At T>130 K, two other optical modes-the average of two other Raman modes observed at higher wave numbers-are required to enhance the fits to the experimental results. In the absence of the anomaly, theta(D) rises from 575 to 593 K, whereas theta(E) decreases slightly to 211 K. The density of states at the Fermi level [approximate to5 (eV unit cell)-1] is comparable to previous reports. The magnetic susceptibility is small and independent of magnetic field and temperature. (C) 2004 American Institute of Physics.