Stable antiferromagnetism and semiconducting-to-metal transition in ALaCuOsO6 (A = Ba and Sr): strain modulations

Abstract

Double perovskite oxides (DPO) with antiferromagnetic ground state have received much consideration as they exhibit small stray-field and ultra-fast spin dynamics, which is extremely convenient for high-density and high-frequency data storage devices. It is a well-established fact that strain can easily tune the physical properties of the materials; therefore, the electronic and magnetic properties of recently synthesized ordered ALaCuOsO₆ (A = Ba and Sr) DPO under biaxial ([110]) strain are investigated using ab initio calculations. Our results revealed that the unstrained systems exhibit semiconducting states having energy band gaps (E_g) of 0.28 and 0.39 eV for A = Ba and Sr, respectively. Along with this, both structures exhibit AFM ground state due to a strong AFM coupling between partially filled high-energy Cu⁺ e¹_g↑ and low-energy empty Os⁺⁵ t⁰_2g↓ orbitals. The calculated partial spin moments of Cu and Os ions are 0.65/0.66 and 1.58/1.60μ_B in a Ba-/Sr-doped system having electronic configurations of 3d⁹ (t³_2g↑t³_2g↓e²_g↑e¹_g↓) with S = 0.5 and 5d³ (t³_2g↑) with S = 1.5, respectively. The robustness of AFM spin ordering is affirmed under the strain effects. The most striking feature of the present study is that Ba- and Sr-doped systems demonstrate an electronic transition from semiconductor to metal at critical tensile strains of +4% and +5% along with improved magnetism as well as Néel temperature, respectively. However, the magnetic ground state remains robust against applied strains in both cases. Hence, the present study shows that strain engineering could be a practical tool to modulate the electronic and magnetic properties of DPO to further enhance their technological applications in spintronics.