Complex magnetism with reentrant spin glass behavior and magnetodielectric effect in La2FeMnO6 double perovskite system

Abstract

In this study, we investigate the influence of magnetic frustration, arising from competing 3d ion interactions, on the structural, magnetic, and dielectric properties of La₂FeMnO₆ (LFMO) double perovskite system. X-ray diffraction (XRD) and DC magnetization measurements confirm the presence of anti-site disorder (ASD), which contributes to complex magnetic behaviors. Multiple glassy transitions are observed: a non-interacting cluster-glass-like state below ∼280 K, an interacting cluster-glass-like state at T_f1 ≈ 85 K, and a spin-glass state at T_f2 ≈12 K. These transitions are further supported by magnetic memory effects and thermal relaxation analysis. AC susceptibility reveals frequency-dependent dispersion, which is explained using the critical slowing model near T_f1 and T_f2​. Interparticle magnetic interactions are analyzed using isothermal remanent magnetization (IRM) and direct current demagnetization (DCD) techniques. Magnetoresistance (MR) and Maxwell–Wagner (MW) relaxation confirm a significant extrinsic magnetodielectric (MD) effect near T ≈ 240 K. Electronic structure calculations indicate a ferrimagnetic insulating state with a narrow band gap, attributed to the high-spin Fe³⁺ and intermediate-spin Mn³⁺ states. This work demonstrates how ASD and competing magnetic interactions drive multiple spin dynamics and distinct magnetic relaxations in the LFMO system.