Improving thermostability of CrO2 thin films by doping with Sn

Chromium dioxide (CrO2) is an ideal material for spin electronic devices since it has almost 100% spin polarization near Fermi level. However, it is thermally unstable and easily decomposes to Cr2O3 even at room temperature. In this study, we try to improve the thermal stability of CrO2 thin films by doping with Sn whose oxide has the same structure as CrO2. High quality epitaxial CrO2 and Sn-doped CrO2 films were grown on single crystalline TiO2 (100) substrates by chemical vapor deposition. Sn4+ ions were believed to be doped into CrO2 lattice and take the lattice positions of Cr4+. The magnetic measurements show that Sn-doping leads to a decrease of magnetocrystalline anisotropy. The thermal stabilities of the films were evaluated by annealing the films at different temperatures. Sn-doped films can withstand a temperature up to 510 °C, significantly higher than what undoped films can do (lower than 435 °C), which suggests that Sn-doping indeed enhances the thermal stability of CrO2 films. Our study also indicates that Sn-doping may not change the essential half metallic properties of CrO2. Therefore, Sn-doped CrO2 is expected to be very promising for applications in spintronic devices.