Transport, magnetic, thermal and structural properties of the spinel compound CuTi2S4

SYNTHESIS AND MAGNETIC PROPERTIES OF CHROMIUM-BASED Cu(Cr2-xTi x)S4 THIOSPINELS AND THEIR DEFICIENT STRUCTURES Cu1-y□yCr2-xTi xS4 OBTAINED BY COPPER EXTRACTION

“…Firstly, the limiting compounds CuCr 2 S 4 and CuTi 2 S 4 represent a ferromagnetic and a Pauli paramagnetic limits, respectively, in which both Ti and Cr can be considered in mixed-valence states. However, Ti 3+ (S = ½) is in a singlet state with no intrinsic effective moment, while Cu has a closed shell (Cu + ; S = 0) 20,26 . Then, all magnetic behavior is due to the chromium contribution, which may be under different configurations, depending on the degree of substitution 27 .…”

“…This compound is known to display a Pauli paramagnetism and a spin singlet ground state 19,20 and behaves as a metal in terms of its electronic structure and transport properties 13 .…”

“…We should however recall some of the main features regarding CuTi 2 S 4 , in particular a temperature-dependent term coming from the high density of states of the Ti 3d bands at the Fermi level 20,26 . This is fairly well observed in CuCr 0.3 Ti 1.7 S 4 (x = 1.7), whose magnetic susceptibility (insert, figure 6) resembles to the intrinsic magnetic susceptibility evaluated by Okada et al 20 for the spinel CuTi 2 S 4 after subtraction of some impurities contribution.…”

“…We should remark that the thermal dependence of the magnetization of CuCr 0.3 Ti 1.7 S 4 shows a tendency to reach a plateau at 50 K, as also reported in ref. 20 for the intrinsic magnetic susceptibility of CuTi 2 S 4 . In our case however, the absolute values of the magnetization for the substituted compound (x = 1.7) are much larger than those reported for CuTi 2 S 4 and therefore, we may conclude that the Ti 3d bands are even narrower than those suggested for the limiting spinel.…”

Phenomenological thermodynamics and the structure formation mechanism of the CuTi2S4rhombohedral phase

“…According to ref. 17 the CuTi 2 S 4 compound has a normal spinel structure at room temperature, where Cu ions occupy the tetrahedral site and Ti ions occupy the octahedral site, which crystallize into a cubic Fd% 3m structure. CuTi 2 S 4 shows the Pauli paramagnetism, and there is no structural phase transition down to 8.3 K. 17 Hence, according to ref.…”