Grain boundary ferromagnetism in vanadium-doped In₂O₃ thin films

Room temperature ferromagnetism was observed in In$_2$O$_3 thin films doped with 5 at.% vanadium, prepared by pulsed laser deposition at substrate temperatures ranging from 300 to 600 $\,^{\circ}{\rm C}$. X-ray absorption fine structure measurement indicated that vanadium was substitutionally dissolved in the In$_2$O$_3$ host lattice, thus excluding the existence of secondary phases of vanadium compounds. Magnetic measurements based on SQUID magnetometry and magnetic circular dichroism confirm that the magnetism is at grain boundaries and also in the grains. The overall magnetization originates from the competing effects between grains and grain boundaries.