Observation of competing magnetic phases, mechanical stability, electronic structure, magnetism, and remarkable thermoelectric aspects of Ba2GdRuO6

Abstract

The Ba₂GdRuO₆ double perovskite oxide demonstrates intriguing behavior, arising from competing antiferromagnetic (AFM) and ferrimagnetic (FiM) phases. Under the GGA+U+SOC scheme, the system exhibits an AFM ground state with a very small energy difference of −11.39 meV compared to the FiM one. In contrast, spin modeling reveals significant magnetic frustrations along the z-axis and favors the FiM phase. Also, the magnetic phase transition discloses a Curie temperature (T_C) of 60 K. Additionally, magnetization measurements also affirm the FiM nature which loses saturation at higher temperatures, indicating a transition from FiM to paramagnetic, above T_C. The electronic structure displays the semiconductor nature owing to a direct energy gap of 1.04/0.89 eV in the AFM/FiM state. The determined spin moments on the Gd(1–2)/Ru(1–2) and Gd(3–4)/Ru(3–4) ions are +6.9/+2.0μ_B and −6.9/−2.0μ_B in the AFM spin–orbit, respectively, while they are +6.89/−2.0 on the Gd(1–4)/Ru(1–4) ion in the FiM one. It is found that the Gd³⁺ and Ru⁴⁺ ions lie in +3(4f⁷) and +4(4d⁴) valence states with electronic configurations [f_{x(x²−3y²)}]↑⁰↓¹ [f_{y(3x²−y²)}]↑⁰↓¹ [f_z(x²−y²)]↑⁰↓¹ [f_xyz]↑⁰↓¹ [f_xz²]↑⁰↓¹ [f_yz²]↑⁰↓¹ [f_z³]↑⁰↓¹ and t³_2g↑t¹_2g↓e⁰_g↑e⁰_g↓ with spin quantum numbers of 7/2 and 1, correspondingly. Furthermore, the mechanical stability of the material is validated by satisfying the Born stability criteria and the ductility is determined using Pugh's ratio . Noticeably, the presence of a positive Cauchy pressure of 66.53 GPa further supports the ionic nature of the motif. Besides, the system illustrates a positive Seebeck coefficient, indicating holes as the dominant charge carriers with the highest value of 279 μV K⁻¹ at 400 K. Remarkably, the system achieves a high figure of merit of 0.86 at 550 K even with the inclusion of lattice thermal conductivity, as well as sustaining excellent thermoelectric performance, suggesting a strong potential for elevated temperature energy harvesting applications along with spintronics.