Structural, optical and magnetic properties of Zn0.97−xAlxCr0.03S nanoparticles

Zn0.97−xAlxCr0.03S (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and 0.12) nanoparticles were synthesized by the chemical co-precipitation method using Ethylene Di-amine Tetra Acetic acid (EDTA) as capping agent. The effect of Al co-dopant on the structural, optical and magnetic properties is discussed on the basis of EDS, SEM, XRD, TEM, SAED, DRS, FTIR, PL, EPR and VSM results. EDS studies indicated the presence of Zn, S, Cr and Al elements in the samples with near stoichiometry. XRD, TEM and SAED studies revealed that samples of all concentrations exhibited cubic structure. The absorption edge in DRS spectra shifted towards higher wavelength with increasing Al concentration indicating a decrease of band gap from 4.05 to 3.85 eV. Enhanced photoluminescence was observed with increasing Al concentration up to 4 at% and beyond this photoluminescence quenching was observed. FTIR spectral studies indicated that EDTA simply co-exists on the surface of the nanoparticles and acts as the capping agent preventing agglomeration of the nanoparticles. EPR spectral studies indicated that the EPR signal intensity, linewidth and number of spins increased with Al concentration. VSM studies revealed that Al co-doping suppressed the room temperature ferromagnetism in ZnS:Cr nanoparticles.