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~ 210 K) than the film on SrTiO₃ (T_N ~ 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 magnetoresistance 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.

_{在这项工作中，我们报告了应变对在 SrTiO 3} (001) 和 LaAlO ₃ (001) 衬底上生长的 Sr ₂ IrO ₄薄膜的物理性质的影响。研究发现，LaAlO ₃上压应变薄膜的反铁磁转变温度（T _N ~ 210 K）低于 SrTiO ₃薄膜（T _N  ~ 230 K）拉应变薄膜，这可能是由改进的层间耦合引起的。 . _{有趣的是，由于 LaAlO 3}上薄膜的赝自旋翻转导致的磁阻远大于 SrTiO _{3上的拉伸应变薄膜。}，并且在前者中观察到稳健的各向异性磁阻，但在后者中观察到H驱动的反转行为。通过执行第一性原理计算，揭示了外延应变在调节J _eff  = 1/2 矩的倾斜角以及因此每个 IrO ₂层的净矩方面发挥着有效的作用，这是薄膜之间磁阻差异的原因。由于J _eff  = 1/2 矩的旋转，SrTiO ₃上薄膜各向异性磁阻的反转可归因于带隙工程。_{然而，理论计算揭示了在 LaAlO 3}上的薄膜中更高的磁晶各向异性能量. 这导致难以驱动J _eff  = 1/2 时刻到达对角线并因此达到亚稳态，从而在定性意义上解释了两个样品之间明显的各向异性磁阻。我们的研究结果表明，应变可以是设计J _eff  = 1/2 反铁磁体 Sr ₂ IrO ₄功能的高效方法。