Substrate-induced strain and its effect in CrO₂ thin films

We report a study of substrate-induced strain and its effect in (100) and (110) CrO₂ thin films deposited on TiO₂ substrates of respective orientations. While the (110) CrO₂ films grow essentially strain-free, the (100) CrO₂ films were found to be strained in all lattice directions—out of plane direction was compressively strained while in-plane directions were under tensile strain. Crystal lattice parameters were determined in strained (100) and strain-free (110) CrO₂ films together with the amount of strain in the three lattice directions. We found substrate-induced strain to significantly affect the magnetic moment in the (100) CrO₂ films at room temperature—reducing the magnetic moment with increasing strain in the (100) films while strain-free (110) CrO₂ thin films have higher moments for all thicknesses. Qualitative macroscopic conductance behavior in the strained (100) and strain-free (110) CrO₂ films were found to be comparable for temperatures in the range of 5–400 K, showing similar behavior at low temperature as well as near T_c.