Effect of progressive substitution of Lu by Ho on the structural and dielectric properties of nanocrystalline LuFeO < inf > 3 < /inf > orthoferrite

Abstract

We report the results of an extensive structural, Raman scattering and dielectric investigation of nanocrystalline Lu1-xHoxFeO3 (0 ≤ x ≤ 1) orthoferrite, synthesized by the hydrothermal method. The Raman modes specific to the rotation of FeO6 octahedra assert that 5 at.% Ho solute concentration suffices to stabilize the orthorhombic structure in the LuFeO3 host. We observed two new Raman modes at ≈ 53 and ≈ 69 cm −1 in all the compositions. The Raman mode Ag (3) [Ag (5)] wavenumber increases linearly with the FeO6 octahedra tilt angle φ[010] [θ[101]], indicating that these independent modes are sensitive to orthorhombic distortion. The real (ε’), imaginary (ε”) parts of the complex dielectric permittivity, measured at room temperature over the ac electric-field frequency range, 20 Hz ≤ f ≤ 2 MHz, unravel two different types of dielectric relaxation in nanocrystalline Lu1-xHoxFeO3.