Growth And Electronic Properties Of Cr₅Te₈ Single Crystal

Since the discovery of ferromagnetism in CrTe compounds,chromium telluride compounds have attracted much attention.In Cr_1-xTe(0<x<0.375)system,many different Cr-Te compounds were obtained with different Cr contents.In this paper,basic cell trigonal Cr₅Te₈is studied.The single crystals were synthesized by Chemical Vapor Transport method,while the temperature difference between the hot part and the cool part of the tubular furnace to avoid the formation of the ordered superlattice products.The high-resolution transmission electron microscopy(HRTEM)samples were prepared by focused ion beam(FIB)technique,and the results showed that the samples were basic cell structure by comparing the slowly annealed Cr₅Te₈with the high-resolution transmission electron microscopy(HRTEM)photos and electron diffraction photos.The crystal structure of the compound was determined by single crystal X-ray diffraction(XRD),and the data of powder refinement reported before was revised.The calculated lattice parameters of the single crystal are a=3.899(?)and c=5.991(?).In this paper,the bond length and bond angle information of Cr₅Te₈single crystal have been re-resolved by single crystal.Cr-Te-Cr bond angle 92.706^o,Cr-Te bond length 2.693(?).At the same time,the temperature dependence of the resistance of the sample was characterized,and the mechanism of the temperature dependence of the resistance was discussed according to the conclusion of Raman spectra at low temperature.By Fano fitting low temperature Raman Spectra,the trend of Raman peak symmetry variation near 20K is found,and it is suggested that the variation of resistivity at 20K may be caused by phonon-electron scattering.The high-pressure structure stability of the samples was studied by Diamond Anvil cell technique combined with X-ray diffraction technique.Ruby is used as the pressure marker to mark the pressure and silicone oil is used as the pressure medium to provide the quasi-hydrostatic pressure.The x-ray diffraction pattern of the sample shifts to a higher angle with the increase of pressure,which shows that the unit cell decreases gradually with the increase of the pressure.The crystal lattice parameters of the sample at different pressures were obtained by Le Bail method,and it was found that a phase transition of crystal structure occurred above 11GPa.With the help of the software Jana 2006,X-Ray diffraction data of the phase under 16 GPa were refined to get the crystal structure which belongs to Pnma space group.After refinement,the unit cell parameters were a=7.1214(?),b=6.5534(?),c=4.2403(?)and V=197.93(?)³.