Absence of the 90 K structural transition in CuV₂S₄crystals grown by chemical vapour transport using TeCl₄

Abstract

Various physical properties (magnetization, specific heat, optical reflectance, electrical resistivity) of CuV 2 S 4 crystals grown by chemical vapour transport using TeCl 4 as the transporting agent have been measured. The data show slight differences compared to samples grown using different techniques. These differences include the absence of a sharp drop in magnetization and the absence of a peak in the heat capacity near 90 K. These differences suggest that the cubictetragonal phase transition near 90 K does not occur in these particular crystals. The reflectance of the same crystals has been studied from (70-20 000 cm −1 ) for temperatures between 40 and 300 K and the data are consistent with those for a disordered metal. A high frequency absorption, perhaps an interband transition, has been observed in addition to absorption due to strongly scattered free carriers.

Correlation between structural and magnetic properties of half‐metallic spinel CuV2S4 due to the order–disorder transition of 3d2(t2g) orbitals of V3+ ions

“…Figure 11a-c show the temperature dependence of the susceptibility at applied magnetic fields of 400 G, 1 kG, and 1 T, respectively. It is found that the weak spike-like susceptibility appearing in the region of about 80 K to 90 K reduces gradually with increasing applied magnetic filed, and disappears at 1 T. The susceptibility curve at 1 T is very simi- T(K) lar to those obtained at applied magnetic fields of 1 T, 3 T, and 5 T for single crystals reported by Crandles et al [7]. From the present investigations of the susceptibility, we deduce that the spike-like susceptibilities appearing in the region of about 40 K to 55 K and of about 80 K to 90 K depend on the specimen -type of fine powders, crystals, and single crystal -in addition to the spatial alignment between the crystallographic axes and the applied magnetic filed.…”

“…9a, the susceptibility does not show any large modulation at 50 K and 90 K and smoothly decreased on heating, while Fig. 9b shows two small modulations at about 55 K and 90 K. However, the susceptibility reported by Crandles et al [7] gradually increased on heating above about 70 K. For comparison, at 80 K and 1 T, the susceptibility is about 4.78 × 10 −6 emu/gOe in Fig. 9.…”

“…9. The susceptibility has been reported to be similar at about 3.4 × 10 −6 emu/gOe [6] and 4.0 × 10 −6 emu/gOe [7].…”

“…Until now, the magnetic susceptibility of CuV 2 S 4 has been reported and showed magnetic anomalies, but not a magnetic phase transition, at about 50 K and 90 K, in addition to the abrupt increase below . However, recently, Crandles et al [7] reported that, for CuV 2 S 4 crystals grown by chemical vapor transport using TeCl 4 , there is an absence of the sharp drop in the magnetization and the peak in the heat capacity near 90 K and that the structural transition from cubic to tetragonal does not occur at about 90 K. Thus, we measured the magnetic susceptibility of the fine powders by using the SQUID instrument to confirm the results [7]. The powder sample was same as that used for the X-ray powder diffraction.…”

“…After the CDW interpretations of the structural, electric, and magnetic anomalies [1], many investigations were carried out of the structural, magnetic, and electric properties of CuV 2 S 4 in the low-temperature region by means of X-ray diffraction [2][3][4][5], magnetic susceptibility [2,3,[5][6][7], electrical resistivity [2,5,[7][8][9][10], and NMR [4][5][6][11][12][13][14], in addition to the electronic density of states (DOS) [15][16][17]. Lu et al [15] argued using X-ray photoemission and X-ray spectroscopy that Cu ions are in the mono-valent state in Structural and magnetic properties of the spinel CuV 2 S 4 have been studied by means of X-ray diffraction using synchrotron radiation and measurements of magnetic susceptibility.…”