Magnetization Effects in Proton Micro-Irradiated Diamond

TL;DR

This study demonstrates that proton micro-irradiation induces ferromagnetic-like states in high purity diamond, with magnetic responses correlating to structural changes such as sp2 carbon formation, as characterized by advanced microscopy and spectroscopy techniques.

Contribution

It provides the first detailed evidence of irradiation-induced room-temperature ferromagnetism in diamond at the microscale, linking magnetic properties to structural modifications.

Findings

Proton micro-irradiation induces magnetic states in diamond.

Magnetic response correlates with sp2 carbon formation.

Room-temperature ferromagnetic-like ordering observed.

Abstract

We report the magnetic response of high purity type IIa single crystal CVD diamond following high energy irradiation by 2.2 MeV proton micro-beams, produced using Nuclear Microprobe techniques. Post-irradiation microanalysis is achieved using Atomic Force, Magnetic Force and Electrostatic Force Microscopy (AFM, MFM & EFM) as well as Raman spectroscopy. Comparison between MFM and EFM measurements at zero electrical bias is used to preclude artefacts of electrostatic origin suggesting the presence of magnetic states in the microscale regions induced by proton micro-irradiation. Analysis of the irradiated regions using probe polarization dependent magnetization measurements shows an irradiation induced magnetic response consistent with ferromagnetic ordering at room temperature. Structural characterization of the micro-irradiated regions using micro-Raman spectroscopy indicates a correlation between formation of the sp2 carbon phase in the diamond matrix with the scale of the observed magnetization, in the investigated experimental regime.