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Magnetic properties of monodispersed Ni/NiO core-shell nanoparticles
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Researchers fabricated monodispersed Ni/NiO core-shell nanoparticles using laser ablation. Size-dependent magnetic properties revealed ferromagnetism above the superparamagnetic limit, influenced by NiO shell coupling and field-assisted anisotropy.
Area of Science:
- Materials Science
- Nanotechnology
- Physics
Background:
- Pulsed laser ablation enables fabrication of monodispersed Ni/NiO core-shell nanoparticles.
- Size classification using a differential mobility analyzer (DMA) controls nanoparticle size from 5 to 20 nm.
- In situ oxidation forms NiO shells on Ni cores, creating core-shell structures.
Discussion:
- Magnetic properties were measured using a superconducting quantum interference device (SQUID) magnetometer on room-temperature deposited films.
- Ferromagnetism was observed in nanoparticles with core diameters below the superparamagnetic limit.
- Weak exchange coupling between the Ni core spin and the antiferromagnetic NiO shell is suggested.
Key Insights:
- Nanoparticles with Ni cores smaller than the superparamagnetic limit exhibit ferromagnetism.
- Ni/NiO nanoparticles with 3.0 nm core diameters display superparamagnetism.
- Magnetic-field-assisted nanostructuring induces strong anisotropy, altering hysteresis loops.
Outlook:
- Further investigation into the exchange coupling mechanism between Ni and NiO is warranted.
- Exploring applications in magnetic storage and spintronics based on tunable magnetic properties.
- Optimizing fabrication parameters for precise control over nanoparticle size and shell thickness.