The magnetic properties of ${\mathrm{Cu}}_{97}{\mathrm{Co}}_3$ and ${\mathrm{Cu}}_{90}{\mathrm{Co}}_{10}$ granular alloys were measured over a wide temperature range $(2–300\mathrm{K})$. The measurements show an unusual temperature dependence of the coercive field. A generalized model is proposed and explains well the experimental behavior over a wide temperature range. The coexistence of blocked and unblocked particles for a given temperature raises difficulties that are solved here by introducing a temperature dependent blocking temperature. An empirical factor gamma $\left(\gamma \right)$ arises from the model and is directly related to the particle interactions. The proposed generalized model describes well the experimental results and can be applied to other single-domain particle system.

• Received 25 October 2003

DOI:https://doi.org/10.1103/PhysRevB.70.014419