Transition from AFM Spin Canting to Spin Glass-AFM Exchange as Particle Size Decreases in LaFeO₃

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Lanthanum ferrite (LaFeO3) is a perovskite oxide with interesting magnetic and structural properties.
• Understanding size-dependent phenomena is crucial for tailoring material functionalities.

Purpose of the Study:

• To investigate the impact of particle size on the structural and magnetic properties of LaFeO3.
• To elucidate the origin of magnetic behaviors in nanoscale LaFeO3.

Main Methods:

• Synthesis of LaFeO3 nanoparticles using the sol-gel method and bulk material via ceramic method.
• Particle size variation through annealing at different temperatures.
• Characterization using X-ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), Thermogravimetric Analysis (TGA), and AC/DC magnetometry.

Main Results:

• Twins observed in bulk LaFeO3 disappear in nanoparticles, correlating with softened FeO6 distortion.
• Spin canting in bulk LaFeO3 vanishes around 125 nm, linked to smoothed orthorhombic distortion.
• Nanoparticles (<60 nm) exhibit exchange bias due to a core-shell structure: spin glass surface and antiferromagnetic core.

Conclusions:

• Particle size significantly influences the structural and magnetic properties of LaFeO3.
• The formation of a magnetic core-shell structure in nanoparticles leads to observable exchange bias.
• These findings offer insights into nanoscale magnetic phenomena in perovskite oxides.