Ferromagnetism in C-doped SnO2 thin films

Abstract

Room temperature ferromagnetism (FM) was observed in laser ablated C-doped SnO2 thin films grown on LaAlO3 substrates. The greatest value of the saturated magnetization (at 1 T) is found in SnO2 films doped with 1% of C (about 16 emu/cm3) and reduces lightly as the C concentration increases. By subtracting the base of pure SnO2 that is also magnetic, one can find that C-doping actually enhances ferromagnetism in the host SnO2. It suggests that carbon really causes defect-induced magnetism of about 3.91 μB/C into SnO2. Measurements on C-doped SnO2 bulks show that the observed properties are unique for films (lower dimensions, having surface/interface effect). The investigation on thickness dependence shows a change in magnetization when going from thin to thick films, implying that somehow if magnetism is due to defects then those must be located more on or near the surface than in deeper layers. Anisotropy is also observed, enforcing the assumption for the origin of magnetism due to defects in C-doped SnO2.