Self Assembly of and Plasmon Enhanced Ultrafast Magnetization in Ag Co Hybrid Nanoparticles

Ultrafast demagnetization in magnetic nanoparticles using pulsed laser has attracted considerable attention because of its potential applications in spintronics, such as data storage. In such applications, it is necessary to control magnetization using low energy laser pulses, however, this poses the problem of increasing the amount of energy from the excitation laser pulses to the spin subsystem. We take advantage of the phenomenon known as localized surface plasmon resonance (LSPR) to enhance the energy transfer from laser pulses to the spin subsystem. To induce LSPR, hybrid nanoparticles consisting of noble metal nanoparticles with LSPR absorption and magnetic metal nanoparticles are prepared using a novel method. Specifically, AgCo hybrid nanoparticles are prepared by a self assembly method using pulsed laser deposition. We performed measurements of the static Faraday and time-resolved Faraday effects using a pump probe technique on the AgCo hybrid nanoparticles with various AgCo ratios. The data suggest that the LSPR absorption and demagnetization amplitude increase with the increasing AgCo ratio. The results indicate that the amount of energy transferred from the laser pulses to the spin system of magnetic nanoparticles can increase via LSPR absorption.