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Structural and Magnetic properties of α–CoV2O6 and Cr doped α–CoV2O6
This study investigates the structural and magnetic properties of α–CoV2O6 and Cr doped α–CoV2O6 samples synthesized through a wet chemical method 1. X-ray diffraction (XRD) revealed that α–CoV2O6 form a monoclinic crystal structure 2, with lattice parameters a = 9.25 Å, b = 3.50 Å, c = 6.63 Å, β = 111.44°, and α = γ = 90°. The crystal is made of linear chains of Co2+ ions along the b–axis, demonstrating the one-dimensional nature of the compound 3. Cr doping resulted in small changes in the lattice parameters and an increase of microstrain in the form of peak broadening 4, accompanied by changes in the crystallite size of the samples. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements show that the particles are aggregated with nonuniform shapes and sizes, with average particle sizes of 141 ± 19 nm, 79 ± 24 nm, and 58 ± 10 nm for α–CoV2O6, α–Co(V0.97Cr0.03)2O6 and α–Co(V0.95Cr0.05)2O2 respectively. The presence of Cr in the doped samples was confirmed through energy dispersive spectroscopy (EDS). Vibrating sample magnetometry (VSM) was used to investigate the magnetic properties of the samples by measuring the temperature dependence of magnetization, M(T) at 0.1 T, 2.5 T, and 5 T, under zero-field-cooled (ZFC) and field-cooled (FC) protocols. The field dependence of magnetization, M(μ0H) and time dependence of magnetization, M(t) were measured. M(T) curves revealed antiferromagnetic (AFM) behavior at 0.1 T with AFM to paramagnetic (PM) transitions increasing from 15 ± 0.2 K for α–CoV2O6 to 15.5 ± 0.2 K for α–Co(V0.95Cr0.05)2O6. M(T) curves measured at 2.5 T reveals a ferrimagnetic (FI) like behavior with spin-glass like irreversibility between ZFC and FC. Ferrimagnetic to paramagnetic transition increase from 13 ± 0.2 K to 13.4 ± 0.2 K with increasing Cr concentration. M(T) at 5 T reveals a ferromagnetic (FM) behavior with a ferromagnetic to paramagnetic transition increasing from 14.4 ± 0.2 K to 15.1 ± 0.2 K. Field-induced metamagnetic transitions were observed in M(μ0H) curves below 15 K for all samples with an increase of saturation magnetization with increasing Cr concentration. M(t) curves at fields between 1.5 and 5 T suggest a spin-glass-like freezing.
References
1 Wang Y et al., ACS Appl. Mater. Interfaces, 8, (2016) 27291–7.
2 Shu H et al., J. Magn. Magn. Mater., 407, (2016) 129–34.
3 He Z et al., J. Am. Chem. Soc., 131, (2009) 7554–5.
4 Khorsand Zak A et al., Solid State Sci., 13, (2011) 251–6.
