Strain tuned magnetotransport of Jeff=1/2 antiferromagnetic Sr2IrO4 thin films

In this work, we report observation of strain effect on physical properties of Sr2IrO4 thin films grown on SrTiO3 (001) and LaAlO3 (001) substrates. It is found that the film on LaAlO3 with compressive strain has a lower antiferromagnetic transition temperature (T-N similar to 210 K) than the film on SrTiO3 (T-N similar to 230 K) with tensile strain, which is probably caused by modified interlayer coupling. Interestingly, magnetoresistance due to pseudospin-flip of the film on LaAlO3 is much larger than that of tensile-strained film on SrTiO3, and robust anisotropic magnetoresistance is observed in the former, but H-driven reversal behavior is seen in the latter. By performing first principles calculations, it is revealed that epitaxial strain plays an efficient role in tuning the canting angle of J(eff) = 1/2 moments and thus net moment at every IrO2 layer, responsible for the difference in magnetoresistance between the films. The reversal of anisotropic magnetoresistance of the thin film on SrTiO3 can be ascribed to bandgap engineering due to the rotation of J(eff) = 1/2 moments. However, theoretical calculations reveal much higher magnetocrystalline anisotropy energy in the film on LaAlO3. This causes difficulties to drive the J(eff) = 1/2 moments to reach the diagonal and thereby the metastable state, explaining the distinct anisotropic magneto -resistance between two samples in a qualitative sense. Our findings indicate that strain can be a highly efficient mean to engineer the functionalities of J(eff) = 1/2 antiferromagnet Sr2IrO4.

Automated summary

In this work, the authors investigate the strain effect on the physical properties of Sr2IrO4 thin films. The film on LaAlO3 substrate with compressive strain has a lower antiferromagnetic transition temperature compared to the film on SrTiO3 substrate with tensile strain. First principles calculations reveal that epitaxial strain plays a role in tuning the canting angle of J(eff) = 1/2 moments, which affects the magnetoresistance of the films. The film on LaAlO3 has higher magnetocrystalline anisotropy energy, causing difficulties in reaching the metastable state and explaining the distinct anisotropic magnetoresistance between the two samples.