Room temperature ferromagnetism in monoclinic Mn-doped ZrO2 thin films

Theory has predicted that high temperature ferromagnetism (FM) should be found in cubic Mn-doped ZrO2. Our experimental data reveal room temperature FM in Mn-doped ZrO2 thin films grown on LaAlO3 substrates. The largest saturated magnetic moment (Ms) is found to be about 13.8 μB/Mn for the cubic Mn0.05Zr0.95O2 films and it decreases as the Mn content increases. In this case, the intrinsic FM is strongly associated with the cubic structure of Mn-doped ZrO2, and the Mn-Mn exchange interactions via intermediate oxygen atoms is important. Room temperature FM is also observed in monoclinic Mn-doped ZrO2 thin films grown on Yttrium Stabilized Zirconia (YSZ) substrates, however, with a completely different nature. Though pristine monoclinic ZrO2 films are already ferromagnetic, doping Mn can enhance the magnetic moment by about 40% (Ms is 2.68 μB/Mn). Differently from the cubic case, FM in monoclinic Mn-doped ZrO2 films does not come only via exchange interactions, but also from defects.