Proton-induced magnetic order in carbon: SQUID measurements

TL;DR

This study investigates how proton irradiation affects the magnetic properties of highly oriented pyrolytic graphite, revealing localized magnetic moments and their dependence on irradiation specifics through SQUID measurements.

Contribution

It provides systematic experimental evidence of proton-induced magnetic order in graphite, confirming previous findings and detailing the dependence on irradiation parameters.

Findings

Localized magnetic moments of about 10^{-10} emu per spot

Magnetic behavior depends strongly on irradiation details

Both para- and ferromagnetic contributions observed

Abstract

In this work we have studied systematically the changes in the magnetic behavior of highly oriented pyrolytic graphite (HOPG) samples after proton irradiation in the MeV energy range. Superconducting quantum interferometer device (SQUID) results obtained from samples with thousands of localized spots of micrometer size as well on samples irradiated with a broad beam confirm previously reported results. Both, the para- and ferromagnetic contributions depend strongly on the irradiation details. The results indicate that the magnetic moment at saturation of spots of micrometer size is of the order of $10^{-10}$ emu.