Antiferromagnetic coupling in Co-doped ZnS

摘要

In this paper, we report room-temperature ferromagnetism in chemically synthesized Zn1−x Co x S (0 ≤ x ≤ 0.10) diluted magnetic semiconductor nanoparticles of ~3–5 nm. The incorporation of Co2+ ion for Zn2+ ions in ZnS lattice and the particle size were confirmed by XRD and TEM along with selected area electron diffraction analysis. UV–Vis measurement showed reduction in the bandgap energy with the increase in Co doping. Maximum magnetization was observed for samples with x = 0.04. From photoluminescence, spectra luminescence efficiency was found to get enhanced on Co doping. Magnetization behavior can be understood to be due to defect-induced ferromagnetism; however, for higher doping concentration, the antiferromagnetic coupling of Co–Co interaction in the close proximity results in the decrease of the overall magnetization of the samples. Moreover, magneto-electronic study also showed a maximum negative magneto-resistance of ~43 % for x = 0.04.