Study of Structural and Magnetic Properties of Doped LuFeO3 for Phase shifting Application using DFT

Abstract

Lutetium iron oxide (LFO) is a type-II multiferroic material which exhibits ferroelectric and magnetic orders, making them interesting for various technological applications include spintronic, memory devices, sensors, and phase shifters. Shifting electric ordering makes LFO a promising material for phase shifting applications due to its unique ferroelectric behavior responsible for change in electronic properties i.e. dielectric constant. Doping strategy is one way to optimize the dielectric constant for specific phase shifting application. The primary aim of this research is to explore the structural and dielectric characteristics of La-doped h-LFO using DFT in CASTEP software. LFO, P63cm phase is investigated using first-principles calculations based on the GGA-PBE approximation with Hubbard U (GGA-PBE+ U) method in the frame of plane-wave pseudo-potential density functional theory (DFT). The indirect band gap of 0.54 eV is calculated from the band structure which converted into direct band gap with value 0.514 eV after doping lanthanum atom at A-site in LFO supercell. The reduction in band gap is due to increase in partial and total density of sates which have great influence on the electric and optical properties. Partial density of states shows increase in total density of states. Lanthanum contributes p-state in the valence band and small contribution from d-state in the conduction band. Substitution of La-atom at the A-site of LFO significantly decreases the dielectric constant from 19.2 to 18.7. A minimal change in electronic disorder is observed due to small difference in the oxidation states of the Lu3+ and La3+as the structure disorder associated with ionic size difference between dopant and substituted atom. The change in the refractive index is also observed from 4.38 to 4.32 and also reflectivity decreases from 0.634 to 0.627.