Nanometers-thick Ferromagnetic Surface Produced by Laser Cutting of Diamond

TL;DR

This study shows that laser cutting of diamond creates a nanometer-thick ferromagnetic surface layer at room temperature, with magnetic properties dependent on surface orientation and removable by chemical or thermal treatment.

Contribution

It demonstrates that laser processing can induce ferromagnetic order on diamond surfaces, revealing a new method to create magnetic features on diamond materials.

Findings

Ferromagnetic response observed only on (100) surface orientation.

Magnetic signals are weaker or absent on other orientations.

Magnetic order is removable by etching or annealing.

Abstract

In this work, we demonstrate that cutting diamond crystals with a laser (532~nm wavelength, 0.5~mJ energy, 200~ns pulse duration at 15~kHz) produces a $\lesssim 20~$nm thick surface layer with magnetic order at room temperature. We have measured the magnetic moment of five natural and six CVD diamond crystals of different size, nitrogen content and surface orientations with a SQUID magnetometer. A robust ferromagnetic response at 300~K is observed only for crystals that were cut with the laser along the (100) surface orientation. The magnetic signals are much weaker for the (110) and negligible for the (111) orientations. We attribute the magnetic order to the disordered graphite layer produced by the laser at the diamond surface. The ferromagnetic signal vanished after chemical etching or after moderate temperature annealing. The obtained results indicate that laser treatment of diamond may pave the way to create ferromagnetic spots at its surface.