Microwave coupled electron tunneling measurement of Co nanoparticles

TL;DR

This study investigates how repeated microwave pulses influence the magnetic switching of Co nanoparticles at low temperature, revealing direct excitation effects and microsecond relaxation times without sample heating.

Contribution

It demonstrates that microwave pulses can directly excite magnetization in Co nanoparticles and characterizes the relaxation time of this excitation.

Findings

Repeated microwave pulses reduce the magnetic switching field.

Microwave pulses do not heat the sample.

Relaxation time of excitation energy is in microseconds.

Abstract

We study electron tunneling through Co nanoparticles in the presence of repeated microwave pulses at 4.2K. While individual pulses are too weak to affect the magnetic switching field, repeated microwave pulses start to reduce the magnetic switching field at 10{\mu}s spacing. We use I-V curve as a thermometer to show that the microwave pulses do not heat the sample, showing that magnetization in Co nanoparticles is directly excited by microwave pulses, and the relaxation time of the excitation energy is in the range of microsecond.