Spontaneous polarization, n-type half-metallicity, low lattice thermal conductivity, and high structure stabilities in F@O-doped PbTiO3

Abstract

Materials displaying ferroelectric and ferromagnetic properties offer a fascinating foundation for future spintronic innovations like multi-state random-access memory and data storage devices. Herein, numerous features of pristine and F@O-doped-PbO (PO)/TiO₂ (TO)-layer PbTiO₃ perovskite oxides are investigated via ab initio calculations. The calculated negative formation enthalpies and elastic coefficients verify the thermodynamic and mechanical stability of the structures, respectively. The pristine motif exhibits a giant spontaneous polarization (P) of 88 μC cm⁻², having a non-magnetic insulating state with an indirect energy gap (E_g) of 2.11 eV. It appears that the dopant reduces the structural distortions, lowering P to 42.56/42.78 μC cm⁻² in the F@O-doped PO/TO-layer-based structure. The most notable aspect of the present study is that F-doping in the PO layer induces an n-type half-metallic (HM) ferromagnetic (FM) behavior with a total magnetic moment (m_t) of 1.0 μ_B. It is found that Ti ions are the main contributor to the magnetism, which is confirmed by spin-magnetization density isosurface plots. Additionally, a large E_g of 2.49 eV in the spin-minority channel is found, which is large enough to ensure the HM state and avoid reverse leakage current. Conversely, the F@O-doped TO-layer-based system transforms to an FM semiconductor with an E_g of 0.23 eV. Interestingly, the highest figure of merit of 0.72/0.56/0.49 is predicted at 700/700/400 K for the pristine/F@O-doped PO/TO-layer-based structures with the inclusion of lattice thermal conductivity. Thus, due to high structural stability, high P, half-metallicity, and low thermal conductivity, the F@O motif emerges as a promising candidate for various potential applications in spintronics and energy conversion.