Huge Inverse Magnetization Generated by Faraday Induction in Nano-Sized Au@Ni Core@Shell Nanoparticles

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Amorphous nickel (Ni) shells on crystalline gold (Au) nanoparticles are investigated for unique magnetic properties.
• Understanding magnetic phenomena in nanoscale systems is crucial for advanced material applications.

Purpose of the Study:

• To report the design and observation of significant inverse magnetizations in Ni-Au nanostructures.
• To investigate the factors influencing this inverse magnetization and its relaxation dynamics.

Main Methods:

• Fabrication of nano-sized amorphous Ni shells on crystalline Au nanoparticles.
• Controlled application and removal of magnetic fields.
• Measurement of inverse magnetization and its relaxation behavior.
• Analysis of the role of eddy currents induced via Faraday induction.

Main Results:

• Observation of large inverse magnetizations (up to 54% of initial magnetization) upon magnetic field removal.
• Inverse magnetization magnitude is highly sensitive to field reduction rate and prior thermal/field history.
• A clear memory effect in the induced inverse magnetization was observed during relaxation measurements.
• Relaxation follows an exponential decay profile, with a critical exponent tunable by waiting time before field removal.

Conclusions:

• The study demonstrates a novel method to induce significant inverse magnetization in Ni-Au nanostructures.
• Eddy currents generated through Faraday induction are identified as the key mechanism.
• The observed memory effect and tunable relaxation dynamics offer potential for applications in magnetic data storage or sensors.