Magnetic and spectroscopic investigation of partially reduced vanadium pentoxides. II. β'-Cu xV 2O 5
The magnetic, electron paramagentic resonance (EPR), infrared (ir), and optical properties of β'-Cu xV 2O 5 have been measured and interpreted. Magentic susceptibility studies indicate that β'-Cu xV 2O 5 undergoes a semiconductor → metal transition near x = 0.60. For x ⩽ 0.40, the magnetic data interpreted in terms of a ligand-field model in which the octahedral 2T2 g term of V 4+ is split by the combined perturbations of axial distortion and spin-oribt coupling, with the result that the 2T2 g term is split into a magnetic ground level, a weakly magentic intermediate level, and a magnetic highest level. The results of the magnetic analysis further support the transition to metallic behavior with increasing x. The EPR spectra are motionally narrowed by electronic hopping at low temperatures, and the g-tensor and linewidth data are in good agreement with the magnetic results. The ir spectra are independent of x and exhibit narrow bands at 1020 and 995 cm -1, which are attributed to the stretching vibration of multiple VO bonds. The optical spectra consist of two main bands whose peak positions shift to higher frequencies with increasing x, implying that the V 4+O bond distances decrease with increasing x. The results of this study are in excellent agreement with Goodenough's interpretation of β- MxV 2O 5.