Magnetism variations and susceptibility hysteresis at the metal-insulator phase transition temperature of VO_2 in a composite film containing vanadium and tungsten oxides

摘要

We report on the magnetic property of 0.67-WO_3 + 0.33-VO_x mixture film deposit on the corning glass substrate using the chemical sol-gel and atmospheric pressure chemical vapor deposition (APCVD) methods. The XRD and Raman spectroscopy confirm species of both materials, and the morphological studies with FIB-SEM and TEM reveal segregation of W and V atoms. XPS reveals that V~(4+) from VO_2 forms only 11% of the film; V~(3+) in the form of V_2O_3 form 1% of the film, 21% is V~(5+) from V_2O_5 and 67% is given to W~(6+) from WO_3. The analysis of the ESR data shows some sharp changes in the magnetism near the metal-to-insulator (MIT), which could be theoretically interpreted as the ordering or alignment of electron spins from net moment nature to parallel alignment of magnetic moment. The derivatives of magnetic susceptibility established the thermally induced magnetic property: two distinct transitions of 339 K for heating data and 338 K for cooling data for 151.2 mT field were obtained. Similar results were also obtained for 308.7 mT field, 336 K for heating data and 335 K for cooling data. VSM results confirm a paramagnetic phase with a small amount of magnetically ordered phase.