Competing magnetic states andM-Hloop splitting in core-shell NiO nanoparticles

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Magnetic relaxation in nanoparticles is influenced by various factors including intra-particle interactions, reversal mechanisms, and defects.
• Understanding competing magnetic states is crucial for designing advanced nanomaterials.

Purpose of the Study:

• To investigate the competing magnetic states between superparamagnetic blocking and Néel transition in core-shell NiO nanoparticles.
• To determine the critical particle size influencing these magnetic states and associated phenomena.

Main Methods:

• Synthesis and characterization of 14 nm core-shell NiO nanoparticles.
• Magnetic measurements including zero field cooled/field cooled magnetization curves at various fields.
• Analysis of M-H loops at a crossover temperature of 50 K.
• Neutron diffraction experiments for structural confirmation.

Main Results:

• A crossover temperature of 50 K was identified for competing superparamagnetic blocking and Néel transition states.
• Anomalous M-H loop splitting, attributed to slow spin relaxation, was observed at the crossover temperature.
• This loop splitting behavior was found to be particle size-dependent, with a critical size around 14 nm for NiO nanoparticles.

Conclusions:

• The study reveals a critical size effect in NiO nanoparticles, governing the interplay between superparamagnetic blocking and Néel transition states.
• The findings offer new insights into intra-particle interactions in antiferromagnetic nanoparticles.
• This research is a significant step towards understanding competing magnetic relaxation modes in nanomaterials.