Abstract
In this work, spinel ferrites (NiCoFe2O4) were prepared as thin films by dc reactive dual-magnetron co-sputtering technique. Effects of some operation parameters, such as inter-electrode distance, and preparation conditions such as mixing ratio of argon and oxygen in the gas mixture, on the structural and spectroscopic characteristics of the prepared samples were studied. For samples prepared at inter-electrode distance of 5 cm, only one functional group of OH- was observed in the FTIR spectra as all bands belonging to the metal-oxygen vibration were observed. Similarly, the XRD results showed that decreasing the pressure of oxygen in the gas mixture lead to grow more crystal planes in the samples prepared at inter-electrode distance of 5 cm. The energy band gap was determined for the sample prepared with mixing ratio of 65:35 and found to be 2.7, 2 and 3.35 eV for direct allowed, direct forbidden and indirect allowed transitions, respectively. The high structural purity was confirmed as no traces for any elements other than Co, Ni, Fe and O were found in the final samples.
Highlights
Ferrites are compound of mixed oxides of iron and one or more other materials which have ferrimagnetic properties
Bands are observed in the infrared spectra of samples with a gas mixing ratio (50:50, 60:40, 75:25, and 80:20)
The absence of obvious peak that due octahedral coordinated metal ions had been noticed and that an indication to lower frequency band (ν2) expected to be around 400 cm-1 only in gas mix ratio (80:20) where observed at 412-450 cm-1. This probably caused by the broadening of this peak attributed to very small particles of spinel ferrites [24]
Summary
Ferrites are compound of mixed oxides of iron and one or more other materials which have ferrimagnetic properties. Amongst all inverse spinel ferrites, the nickel substituted cobalt ferrite has been extensively studied in view of their good chemical and thermal stability, high electrical resistivity, magnetic anisotropy, high coercivity, and moderate saturation magnetization, various exchange interactions and super-paramagnetism, etc. They exhibit ferrimagnetism, originating from the magnetic moment of anti-parallel spins between Fe3+ ions at tetrahedral sites and Co2+ or Ni2+ ions at octahedral sites [16]. Co-sputtering was accomplished with either two small, usually round cathodes [19, 20] or a multicomponent, tailored target [21]
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