Dominancy of antiferromagnetism in Zn1-xCoxO diluted magnetic semiconductors

Abstract

The outline of magnetic interactions in DMSs was determined using Zn1-xCoxO particles, where "x" was changed as 0.01, 0.05, 0.10, 0.15, and 0.20. The syntheses were accomplished though mechanical milling and thermal treatment, known as solid state reaction. The formation of each synthesis was monitored by differential thermal and thermo gravimetric methods (DT-TGA). Substitution of Co2+ ions with Zn2+ host atoms in a ZnO lattice was analyzed using X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectrometry (EDS) data, transmission electron microscopy (TEM) figures, scanning area electron diffraction (SAED) patterns, and X-ray photo spectroscopy (XPS) spectrum. The measured Co contents in ZnO lattice were found to be similar to 0.7% less than the expected result. In addition to Zn1-xCoxO particles, tungsten (W) contaminations were noticed in the variations of 1.5 +/- 0.2%, as originating from the abrasion between the miller and balls. The progressive replacement of Co2+ with Zn2+ host ions in ZnO lattice from 1% to 20% decreased the band edge from 3.03 +/- 0.01 eV to 2.95 +/- 0.01 eV, respectively. Co doping has also changed the magnetic nature of the ZnO. Although having both interactions (ferromagnetic and antiferromagnetic), dominance of ferromagnetic behavior was only observed for Zn0.99Co0.01O with the coercivity of similar to 154 +/- 50 Oe and positive Curie-Weiss temperature as 79 +/- 1 K. However, the calculated 2J(ex)/k(B) values have proved that the higher Co2+ concentrations in ZnO lattice have increased the efficiency of antiferromagnetic interactions. Surprisingly, there was no rapid change at 2J(ex)/k(B) values as mentioned in previous works.