A. Khanjani, A. Ghasemi, M. Hadi,
Volume 35, Issue 1 (6-2016)
Abstract
In the present research NdFeB thin films coupled with buffer and capping layer of W were formed on Si/SiO2 substrate by means of RF magnetron sputtering. The system was annealed at vaccum at different temperatures of 450, 500, 550,. 600 and 650 °C Phase analysis was carried out by XRD and it was found that NdFeB was formed without the formation of any kind of secondary phase. The cross sectional and grain size of the thin films were measured by scanning electron microscopy. Morphological studies were performed by atomic force microscopy. Magnetic properties of thin films including coercivity, saturation of magnetization and hysteresis area were evcaluated by vibrating sample magnetometer. It was found that by annealing at 400 °C the amorphous layer was formed.The highest intensity of peaks was formed at 550 °C and with an increase in temperature the intensity was declined. The grain size was increased by temperature and had an impact on the coercivity. With an increase of temperature up to 600 °C, perpendicular coercivity was increased and then by further increase of temperatute, coercivity was reduced. Based on the obtained data the temperature of 600 °C was selected as the optimum annealing temperature for reaching enhanced structural and magnetic feature.
M. Hakimi, P. Kameli, B. Aslibeiki, A. Faqeeh,
Volume 35, Issue 4 (2-2017)
Abstract
In this work, cobalt ferrite nanocrystallites were synthesized by air annealing of milled Co-Fe compound. Effect of annealing temperature on phase formation of cobalt ferrite and structural and magnetic properties of the product was studied. Analysis of annealed sample in 450 oC showed that around 46 weight percent of the specimen was changed to Co2FeO4. This value increased to 95 and 90% for 800 oC and 900 oC annealed samples respectively. Reduction of saturation magnetization under annealing was related to transformation of Co-Fe to cobalt ferrite. Increasing the value of saturation magnetization in 900 oC annealed sample compared to 800 oC one was attributed to decreased surface to volume ratio and crystallite size. The main reason of occurrence of maximum coercivity in 800 oC annealed sample was its low crystallite size.
M. Hakimi, M. Safari,
Volume 38, Issue 1 (6-2019)
Abstract
In this study, the improvement of the magnetic properties of Co2FeSi Heusler compound was followed by the utilization of different experimental synthesizing procedures. Comparing the crystal structure showed that the milled samples had a higher crystalline order than the arc-melted ones. Annealing of the milled sample improved the crystalline order, resulting in the highest saturation magnetization (5/24 μB/F.u.). The difference in the saturation magnetization of the other samples was explained by the core-shell model. Comparison of the various coercivity mechanisms showed that the decrease in the size of crystallites played a key role in the higher value of the milled samples coercivity.
