In this work, we propose exchange-coupled-composite-bit-patterned media (ECC-BPM) with microwave-assisted magnetic recording (MAMR) to improve the writability of the magnetic media at a 4 Tb/in2 recording density. The suitable values of the applied microwave field’s frequency and the exchange coupling between magnetic dots, Adot, of the proposed media were evaluated. It was found that the magnitude of the switching field, Hsw, of the bilayer ECC-BPM is significantly lower than that of a conventional BPM. Additionally, using the MAMR enables further reduction of Hsw of the ECC-BPM. The suitable frequency of the applied microwave field for the proposed media is 5 GHz. The dependence of Adot on the Hsw was additionally examined, showing that the Adot of 0.14 pJ/m is the most suitable value for the proposed bilayer ECC-BPM. The physical explanation of the Hsw of the media under a variation of MAMR and Adot was given. Hysteresis loops and the magnetic domain of the media were characterized to provide further details on the results. The lowest Hsw found in our proposed media is 12.2 kOe, achieved by the bilayer ECC-BPM with an Adot of 0.14 pJ/m using a 5 GHz MAMR.

Multilayer polarization beam splitters (MPBSs) are important optical components in optical communication systems and optical devices. The components of transverse electric (TE) and transverse magnetic (TM) light plane wave in MPBSs are separated in different ways. In this paper, the Pareto optimization (multiobjective evolutionary and genetic algorithms) is used to design MPBSs on C-band frequency. The reflectances of TM light plane wave for Pareto optimization are the lowest and zero at the wavelength of 1.535 μm. The degree of polarization for Pareto optimization is the highest at wavelength from 1.528 - 1.54 μm and reaches 100% at wavelength of 1.535 μm.

Microwave assisted magnetic recording is one interesting magnetic recording technology to improve writability for high areal density of hard disk drive. In this work, the role of intergrain and intragrain coupling and microwave field is investigated by micromagnetic simulation based on the Landau - Lifshitz - Gilbert equation. The results show that the switching field, Hsw, of media with microwave field, Hac, of 10 GHz is lower than that for media without Hac. The exchange coupling between nearest neighbor grains hardly affects the Hsw of media and slightly affects the slope of hysteresis loop. In addition, the slope of hysteresis loops and Hsw decrease with increasing exchange coupling in each grain. The results from this work can lead to obtain the improvement writability and increasing areal density of hard disk drive.

The porous alumina templates were synthesized by anodization process. For preparation, the aluminum foils were cleaned by acetone acid and ethanol. After that, cleaned foils were firstly anodized by oxalic acid with direct current (DC) voltage source. When the first anodization process was complete, the aluminum foils were etched by chromic and phosphoric acid for an hour and then they were secondarily anodized for 15 min to increase the pore depth. For characterization, the surface morphology of porous alumina on aluminum surface was evaluated by scanning electron microscope. The results show that the pore diameter increases with increasing DC voltage and concentration of oxalic acid. The lowest pore diameter is 57.19 nm at DC voltage of 20 V for concentration of 0.2 M that it has highest pores density of 157 Gpores/in2.

To overcome superparamagnetic limit, microwave assisted magnetic recording (MAMR) is one interesting magnetic recording technology. Therefore, the effect of microwave on magnetization reversal in media should be analyzed. In this work, we propose the MAMR to decrease switching field (coercivity, Hsw) in exchange coupled composite (ECC) media by using the micromagnetic simulation based on the Landau - Lifshitz - Gilbert equation. The Hsw of single layer and ECC media without microwave field is 110.90 and 7.7 kOe, respectively. When the oscillating microwave field is added, Hsw of single layer media with microwave frequency of 2.5 - 40 GHz is lower than 110.90 kOe. Likewise, Hsw of ECC media with microwave frequency of 5 - 16 GHz is lower than 7.7 kOe and has the lowest value of 4.9 kOe at frequency of 10 GHz. The results from this work lead to solve superparamagnetic limit and increase areal density in hard disk drive.