| Autor: |
Thomas Moyo, H. M. I. Abdallah, Nadir S. E. Osman, Itegbeyogene P. Ezekiel |
| Rok vydání: |
2014 |
| Předmět: |
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| Zdroj: |
Journal of Magnetism and Magnetic Materials. 365:83-87 |
| ISSN: |
0304-8853 |
| DOI: |
10.1016/j.jmmm.2014.04.041 |
| Popis: |
The nanoparticle Sr 0.5 Co 0.5 Fe 2 O 4 powder was produced via glycol-thermal process from high-purity metal chlorides at a low reaction temperature of 200 °C. The phase identification of the as-synthesized powder reveals cubic spinel structure with an average crystallite size of 8 nm. Room-temperature Mossbauer spectra for the as-synthesized sample and samples annealed at different temperatures show different local environments of tetrahedral and octahedral coordinated iron cations. Magnetic properties of the as-synthesized sample and samples annealed at 300, 400, 450, 500, 600, 700 and 800 °C have been investigated using a vibrating sample magnetometer at room-temperature in applied magnetic fields of up to about 1.4 T. A substantial increase in coercive field at 300 K from 0.28 kOe to 2.897 kOe was obtained for the as-synthesized and annealed sample at 800 °C. Magnetic field dependence of magnetization curves measured on a mini-cryogen free VTI system operating at a base temperature of 2 K in magnetic fields of up to 5 T have been investigated. The variation of the saturation magnetization as a function of temperature follows modified Bloch׳s law. Coercive field increased from about 0.28 kOe and 1.04 kOe at 300 K to 11.14 kOe and 10.43 kOe at 2 K for the as-synthesized sample and sample annealed at 500 °C, respectively because of spin-freezing. The effect of exchange bias and Kneller׳s law are used to account for the temperature dependence of coercive fields. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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