Room-temperature ferromagnetism in EDTA capped Cr-doped ZnS nanoparticles

Cr-doped ZnS nanoparticles with Cr concentrations of 0.5, 1, 2 and 3 atm.% were successfully synthesized by the chemical co-precipitation method using ethylenediaminetetraacetic acid (EDTA) as the capping agent. The structural, optical and magnetic properties of the prepared samples were studied. Energy dispersive spectroscopy (EDS) measurements showed the presence of Cr in the Cr-doped ZnS. No mixed phase was observed from X-ray diffraction (XRD) studies and all the peaks were indexed to the cubic phase of ZnS. The average diameter of the particles was in the range of 6-10 nm, and it was confirmed by TEM studies. The magnetic behavior of the nanoparticles for different chromium concentrations was investigated by magnetism measurements using a vibrating sample magnetometer (VSM). The nanoparticles with lower Cr concentration exhibited strong ferromagnetism, where as in samples of higher Cr concentrations the ferromagnetism suppressed. The electron paramagnetic resonance (EPR) spectra of the nanocrystals showed the resonance of electron centers with a g-value of 1.989. The signal intensity and linewidth of the EPR signal increased with increasing Cr content. FTIR studies indicated that the nanoparticles were sterically stabilized by EDTA.