FERROMAGNETISM IN MECHANICALLY MILLED PURE SnO₂

Abstract

Pure SnO 2 based wide band gap semiconductors were prepared by mechanical alloying method by using steel and tungsten carbide vials. They were further annealed at 900°C. The XRD patterns could be refined by using P4 2 / mnm space group with typical lattice parameters a = b = 4.7322 Å and c = 3.1848 Å. The as milled powders obtained from both the vials exhibit room temperature ferromagnetism (FM) without any transition element doping. However upon annealing, the FM was destroyed in one of the samples. The observed FM is explained in terms of oxygen vacancy and defects induced electrons and exchange interaction between them. The ferromagnetic transition temperature obtained from the temperature variation of magnetization was found to be 915 K. The initial magnetization data could be analyzed in terms of bound magnetic polaron model. The resonance field shift in electron spin resonance spectrum is explained in terms of observed ferromagnetism.