Effect of induced shape anisotropy on magnetic properties of ferromagnetic cobalt nanocubes

TL;DR

This study synthesizes ferromagnetic cobalt nanocubes with controlled shape anisotropy and investigates how this anisotropy influences their static and dynamic magnetic properties, revealing enhanced coercivity and susceptibility effects.

Contribution

It introduces a method to induce shape anisotropy in cobalt nanocubes and systematically studies its impact on magnetic behavior across different sizes and temperatures.

Findings

Shape anisotropy increases coercive fields.

Anisotropy affects transverse susceptibility ratios.

Magnetic properties are size and temperature dependent.

Abstract

We report on the synthesis of ferromagnetic cobalt nanocubes of various sizes using thermal pyrolysis method and the effect of shape anisotropy on the static and dynamic magnetic properties were studied. Shape anisotropy of approximately 10 % was introduced in nanocubes by making nanodiscs using a linear chain amine surfactant during synthesis process. It has been observed that, ferromagnetism persisted above room temperature and a sharp drop in magnetic moment at low temperatures in zero-field cooled magnetization may be associated with the spin disorder due to the effective anisotropy present in the system. Dynamic magnetic properties were studied using RF transverse susceptibility measurements at different temperatures and the singularities due to anisotropy fields were probed at low temperatures. Symmetrically located broad peaks are observed in the frozen state at the effective anisotropy fields and the peak structure is strongly affected by shape anisotropy and temperature. Irrespective of size the shape anisotropy gave rise to higher coercive fields and larger transverse susceptibility ratio at all temperatures. The role of shape anisotropy and the size of the particles on the observed magnetic behaviour were discussed.