# Core and surface structure and magnetic properties of mechano-synthesized LaFeO3 nanoparticles and their Eu3+-doped and Eu3+/Cr3+-co-doped variants

## TL;DR

This paper studies the structure and magnetic properties of LaFeO3 nanoparticles and their doped variants, revealing changes in structure and enhanced magnetization due to doping.

## Contribution

The study introduces Eu3+ and Eu3+/Cr3+ doping in LaFeO3 nanoparticles and reveals their structural and magnetic behavior.

## Key findings

- Doping causes a structural transition from O′-type to O-type in LaFeO3 nanoparticles.
- Eu3+ doping increases magnetization and exhibits van Vleck paramagnetism and Curie–Weiss behavior.
- Anomalous magnetic hardening and exchange bias are observed due to competing anisotropy and magnetoelectric coupling.

## Abstract

The core and surface structure and magnetic properties of mechano synthesized LaFeO3 nanoparticles (30–40 nm), their Eu3+-doped (La0.70Eu0.30FeO3), and Eu3+/Cr3+ co-doped (La0.70Eu0.30Fe0.95Cr0.05O3) variants are reported. Doping results in a transition from the O′-type to the O-type distorted structure. Traces of reactants, intermediate phases, and a small amount of Eu2+ ions were detected on the surfaces of the nanoparticles. The nanoparticles consist of antiferromagnetic cores flanked by ferromagnetic shells. The Eu3+ dopant ions enhance the magnetization values relative to those of the pristine nanoparticles and result in magnetic susceptibilities compatible with the presence of Eu3+ van Vleck paramagnetism of spin–orbit coupling constant (λ = 363 cm−1) and a low temperature Curie–Weiss like behavior associated with the minority Eu2+ ions. Anomalous temperature-dependent magnetic hardening due to competing magnetic anisotropy and magnetoelectric coupling effects together with a temperature-dependent dopant-sensitive exchange bias, caused by thermally activated spin reversals at the core of the nanoparticles, were observed.