Tuning the magnetic properties of Co nanoparticles by Pt capping

TL;DR

This study demonstrates how capping cobalt nanoparticles with platinum modifies their magnetic behavior, increasing blocking temperature and inducing ferromagnetic coupling at higher Pt thicknesses, with potential implications for magnetic nanomaterials.

Contribution

It reveals the effect of Pt capping on Co nanoparticle magnetic properties, showing a transition from superparamagnetic to ferromagnetic-like behavior with increasing Pt thickness.

Findings

Blocking temperature increases from 16 K to 108 K with more Pt.

Pt capping induces a transition to ferromagnetic-like state at >1 nm thickness.

Pd capping produces similar magnetic modifications.

Abstract

We show that by capping Co nanoparticles with small amounts of Pt strong changes of the magnetic properties can be induced. The Co nanoparticles have a mean diameter of 2.7 nm. From magnetometry measurements we find that for zero and for small amounts of Pt (nominal thickness t(Pt) < 0.7 nm) the nanoparticles behave superparamagnetic like. With increasing t(Pt) the blocking temperature is enhanced from 16 up to 108 K. Capping with Pd yields comparable results. However, for values t(Pt) > 1 nm a strongly coupled state is encountered resembling a ferromagnet with a T_c approx. 400 K