Weak electron irradiation suppresses the anomalous magnetization of N-doped diamond crystals

TL;DR

This study demonstrates that low-fluence electron irradiation reduces magnetic hysteresis in nitrogen-doped diamond by decreasing C-centre concentration, highlighting the pivotal role of these centres in magnetic phenomena at relatively high temperatures.

Contribution

It reveals that electron irradiation suppresses magnetic hysteresis in N-doped diamond by reducing C-centre concentration, a novel insight into controlling diamond magnetism.

Findings

Electron irradiation decreases C-centre concentration by up to 40 ppm.

Magnetic hysteresis is suppressed below 30 K after irradiation.

High-temperature annealing partially restores hysteretic behavior.

Abstract

Several diamond bulk crystals with a concentration of electrically neutral single substitutional nitrogen atoms of $\lesssim 80~$ppm, the so-called C- or P1-centres, were irradiated with electrons at 10 MeV energy and low fluence. The results show a complete suppression of the irreversible behavior in field and temperature of the magnetization below $\sim 30$~K, after a decrease of $\lesssim 40~$ppm in the concentration of C-centres produced by the electron irradiation. This result indicates that magnetic C-centres are at the origin of the large hysteretic behavior found recently in nitrogen-doped diamond crystals. This is remarkable because of the relatively low density of C-centres, stressing the extraordinary role of the C-centres in triggering those phenomena in diamond at relatively high temperatures. After annealing the samples at high temperatures in vacuum, the hysteretic behavior is partially recovered.