Magnetic properties of point defects in proton irradiated diamond

• Proton macro-irradiation of pure diamond creates fluence dependent paramagnetism.
• The effective magnetic moment is found to be in the range μeff~(0.1–0.2)μB.
• No evidence of long range magnetic ordering is observed.

We investigate the magnetic properties of ultra-pure type-IIa diamond following irradiation with proton beams of ≈1–2 MeV energy. SQUID magnetometry indicate the formation of Curie type paramagnetism according to the Curie law. Raman and Photoluminescence spectroscopy measurements show that the primary structural features created by proton irradiation are the centers: GR1, ND1, TR12 and 3H. The Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulations together with SQUID observations show a strong correlation between vacancy production, proton fluence and the paramagnetic factor. At an average surface vacancy spacing of ≈1–1.6 nm and bulk (peak) vacancy spacing of ≈0.3-0.5 nm Curie paramagnetism is induced by formation of ND1 centres with an effective magnetic moment μeff~(0.1–0.2)μB. No evidence of long range magnetic ordering is observed in the temperature range 4.2-300 K.