Room temperature ferromagnetism of Sn 1− xCr xO 2 films fabricated by sol–gel method

Abstract

Diluted magnetic semiconductors (DMSs) have been intensively studied recently due to the application in spintronics. Sn 1− x Cr x O 2 thin films with x = 0.016–0.18 were fabricated by sol–gel method and spin-coated on Si (1 1 1) substrates. X-ray diffraction (XRD) patterns show that all samples have pure rutile structure, and no Cr clusters or Cr oxides were detected. X-ray photoelectron spectrum (XPS) reveals that Cr ions in our samples have a chemical valence of 3+. The magnetic measurements were performed by vibrating sample magnetometer. All samples exhibit room temperature ferromagnetism (RTFM) and the magnetic moment per Cr ion drops rapidly with the increase of Cr content because antiferromagnetic super-exchange interaction takes place within the neighbour Cr 3+ ions through O 2− ions for the samples with higher Cr doping. The origin of room temperature ferromagnetism (RTFM) has been interpreted in terms of a bound magnetic polaron (BMP) model. The further annealing experiment results show that the oxygen vacancies play a crucial role in producing ferromagnetism in Sn 1− x Cr x O 2 films.