The magnetization in (Zn 1-x Co x )Ga 2 O 4 ( x = 0.05, 0.10, and 0.20) diluted magnetic semiconductors depending on Co
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esent study describes magnetic interactions in (Zn1–xCox)Ga2O4 (x 5 0.05, 0.10, and 0.20) particles dependant on Co atoms in both tetrahedral and octahedral sites. The effects of substituted Co atoms to magnetic character are analyzed using Curie–Weiss law. The ferromagnetic character is found dominant in (Zn1–xCox)Ga2O4 semiconductors for x values lower than 0.10; in addition, a specific hysteresis with 139 6 50 Oe coercivity is observed for 5% Co-doped ZnGa2O4. The high Co amount in tetrahedral site increased the number of antiferromagnetic couplings and the hysteresis at 300 K disappeared for (Zn0.80Co0.20)Ga2O4 particles. Furthermore, the Co13 ions in the octahedral site decreased leff values, per Co amounts, in the range of 4.89 6 0.01 lB/Co to 4.44 6 0.02 lB/Co, because of enhancing paramagnetic behaviors.
I. INTRODUCTION
As promising materials in spintronic applications, diluted magnetic semiconductors have become one of the widest investigated subjects in the past decades.1,2 The research on possible practical applications could not succeed in having the Curie temperature above room temperature. Nevertheless, due to theoretical findings showing Curie temperature above room temperature, demand has continued for wide band gap semiconductors. In these types of semiconductors, high Curie temperature value originates from shallow energy levels because of defects3 or doped transition-metal atoms4 in the lattice. The oxide semiconductors, such as ZnO, TiO, SnO2 etc., among the wide band semiconductors are thus those mostly in demand, because of their inherent tunable ferromagnetism with high Curie temperature.5–11 One such wide band gap oxide semiconductor, zinc gallium oxide (ZnGa2 O4 ), is broadly utilized for various technological applications as transparent conducting oxides such as in solar cell,12–14 light emitting diodes, 15 power electronics, 16 and solar-blind UV thin film detectors.17 ZnGa2O4 lattice consists of Zn and Ga atoms in tetrahedral and octahedral coordinated with oxygen, respectively, and its band gap is about 4.4 eV.15–17 The zinc gallate (ZnGa2O4) crystal structure is a normal spinel structure, which is defined as a cubic phase with Fd 3m space group.18 The crystal structures lead the band gap of semiconductors, and the doping with either rare a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.86 1062
J. Mater. Res., Vol. 29, No. 9, May 14, 2014
http://journals.cambridge.org
Downloaded: 14 Mar 2015
earth elements (Eu, Cr, Dy etc.) or transition metals (Co, Mn etc.) is generally used to tune the band gap.19–21 The reported dopants for ZnGa2 O4 semiconductors are Co 21, Mn 21, Ge41, Li 1, Se ions, Eu 13 , Cr 31, Dy 31, Mo ions, and Rh 31, to rearrange band gap, and thus the optical and electronic properties. 22–28 Studies indicate that doping with Ge 41, Li1, Mn 21, and Se ions holds promise for potential applications in field-emission display devices with high brightness operating in green spectral regions. 22–24 The doping with Eu 13 and Cr 13
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