Room temperature ferromagnetism in Mn- and Fe-doped indium tin oxide thin films

Undoped and transition-metal doped indium tin oxide films have been grown by pulsed laser deposition technique, on single crystalline c-plane (0001) and r-plane (1102) sapphire substrates maintained at 500–850°C. Magnetization measurements of films deposited at different temperatures indicate that ferromagnetism appears for deposition temperatures, Tdep>600°C, with the highest moment for films deposited around 750°C. Qualitative different ferromagnetic behavior has been observed at room temperature in Fe- and Mn-doped thin films. The stable, hysteretic ferromagnetism of the Fe-doped films is due to the presence of magnetite, as seen in transmission Mössbauer spectra. The Mn-doped films show anhysteretic ferromagnetism which decays over time. It is somehow intrinsic, but not due to the Mn ions, which remains paramagnetic down to 4K. No anomalous Hall effect is observed.