In this study, dynamic magnetization of square model CoFe and CoFeB ferromagnetic materials were observed using micromagnetic simulation based on LLG equation. The geometrical side size was varied from 50 to 500 nm with the thickness of 5 nm and 10 nm. For simulation process, the used damping factor was 0.05 and the cell size of 2.5×2.5×2.5 nm3 was used with respect to exchange length of CoFe and CoFeB. The external magnetic fields were applied in in-plane and out-plane direction to generate magnetic hysteresis loop. It is found that the coercivity decreased as square size increased for both in-plane and out-plane magnetization direction. The coercivity were around 40 to 200 mT for in-plane field magnetization of CoFe. The coercivity tends to constant at 40 mT in diameter less than 100 nm and zero coercivity for diameter greater than 100 nm for out-plane field magnetization. Compared to CoFe, the coercivity in out-plane field is higher than in-plane field in CoFeB square. It is also observed that the switching time and nucleation field increased as the size increased in out-plane direction of both CoFe and CoFeB. The results showed that the different characteristics of magnetic anisotropy of both materials are important in the development of high density magnetic storage.

In this work, hysteresis loop of CoFe and CoFeB disk ferromagnets are observed by using micromagnetic simulation OOMMF based on LLG equation. The diameter varied from 50–500 nm with the thickness 5 nm and 10 nm. For simulation process, the damping factor of 0.05 and the cell size 2.5 × 2.5 × 2.5 nm3 were fixed. We applied parallel and perpendicular external field to generate hysteresis loop of CoFe and CoFeB disk ferromagnets. Interestingly, we found two behaviours of coercivity, first less than diameter 100 nm and second, greater than 100 nm. For parallel-applied field of CoFe and CoFeB, the coercivity showed fluctuation around 20–160 mT. Greater than diameter 100 nm, the coercivity in a constant value around 40 mT for CoFe and around 20 mT for CoFeB. For perpendicular applied field of CoFe, we still observed the coercivity around 40 mT but greater than 100 nm, the coercivity dropped to zero. For CoFeB with perpendicular applied field, the coercivity decrease as the diameter increase until reach diameter 100 nm. Greater than the diameter 100 nm, the coercivity is constant at 20 mT. According to the results, we had observed the Perpendicular Magnetic Anisotropy (PMA) behaviour in both CoFe and CoFeB disk ferromagnets with certain value of the coercivity when the field applied in perpendicular direction.

The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreover, the optimum ratio of Fe/Co was determined after the survey on different alloys with varying Fe/Co ratio resulting in the maximum saturation magnetization while keeping the coercivity low. After optimization, the highest saturation magnetization of 1.62 T was achieved with coercity of 11 A/m. While substitution of Hf for Zr slightly reduced the crystallization onset temperature of the amorphous structure, the thermal stability of the soft magnetic amorphous alloys was not significantly affected by the Zr/Hf replacement.

Polycrystalline series sample of Nd(x)Sr(1-x)MnO3 (x = 0.3; 0.7 and 0.9) has been prepared with sol-gel method. Refinement result from X-ray diffractometer shows that the sample are crystallize in the same orthorhombic structure with different space group of Imma and Pnma. Scanning Electron Microscope result also indicated that the different amount of substitution modified the grain size and both particle and crystallite size. After all, Nd0.7Sr0.3MnO3 has the largest cell volume followed by the largest grain and crystallite size compared to other two samples. Therefore, each different amount of substitution into the sample will give different impact and further investigation were needed to explore its relation to the physical properties.

The series sample of Nd(1-x)Sr(x)MnO3 (x = 0; 0.5 and 0.1) has been prepared with sol-gel method. The elemental compound or chemical characterization of Nd(1-x)Sr(x)MnO3 (x = 0; 0.5 and 0.1) were obtain using Energy Dispersive X-Ray Spectroscopy (EDS). The EDS results show that the elements were all presents in the sample, which also verified that the sample has successfully synthesized. The Vibrating Sample Magnetometer (VSM) was used to measure the magnetic properties of the sample under room temperature. The results show that the material is all soft magnetic with the magnetization decrease as the temperature decrease.