Effects of vacancy and lattice distortion on ferromagnetism in sputtered epitaxial Sn1−xKxO2 films

• (100)-orientated Sn1−xKxO2 films were deposited on the (0001) surface of sapphire.
• Three distinct symmetry equivalent in-plane orientations were observed.
• The ferromagnetism enhances monotonously with doping, which is established through p–p coupling interaction.
• The lattice distortion will disturb the arrangement of the electrons and can be remitted by post-thermal treatment.

Structures, optical and magnetic properties of epitaxial Sn1−xKxO2 films were investigated experimentally. Three distinct symmetry equivalent in-plane orientations were observed between the film and substrate. The ferromagnetism enhances monotonously with doping and the largest saturation magnetization is 7.88 emu/cm3 in Sn0.92K0.08O2 film. Generated K interstitials may give rise to a symmetry-lowering distortion of the surrounding lattice. The alignment of magnetic moments in Sn1−xKxO2 films is established through p–p coupling interaction between the impurity p states and host p states. The lattice distortion induced by K at both interstitial site and substitution site will disturb the arrangement of the electrons and can be remitted by post-thermal treatment.