Ab-initio calculation and experimental observation of room temperature ferromagnetism in 50 keV nitrogen implanted rutile TiO₂

Room temperature magnetic properties of 50 keV N⁴⁺ ion beam implanted rutile TiO₂ have been theoretically and experimentally studied. Ab-initio calculation under the frame work of density functional theory has been carried out to study the magnetic properties of the different possible nitrogen related defects in TiO₂. Spin polarized density of states calculation suggests that both N_inst and N_O can induce ferromagnetic ordering in rutile TiO₂. In both cases the 2p orbital electrons of nitrogen atom give rise to the magnetic moment in TiO₂. The possibility of the formation of N₂ molecule in TiO₂ system is also studied but in this case no significant magnetic moment has been observed. The magnetic measurements, using SQUID magnetometer, results a ferromagnetic ordering even at room temperature for the 50 keV N⁴⁺ ion beam implanted rutile TiO₂. (paper)