Research Institute of Advanced Technology

Jeju, South Korea

Research Institute of Advanced Technology

Jeju, South Korea

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Hosaka S.,Gunma University | Mohamad Z.,Gunma University | Yin Y.,Gunma University | Sakurai H.,Gunma University | And 4 more authors.
Key Engineering Materials | Year: 2013

We have studied the coercive force of fine magnetic CoPt dot enhanced by nanometer-sizing of the dot. The 39- to 106-nm-sized CoPt magnetic dot arrays were formed by30-keV-electron beam (EB) drawing with thin calixarene resist and 200-eV-Ar ion milling. Using the fine magnetic dot arrays, we measured coercive forces of the dot by x-ray magnetic circular dichroism (XMCD) with an energy of 11.56 keV, which corresponds to an energy edge of Pt-L3. It is experimentally demonstrated that a coercive force of the nanometer-sized magnetic column increased as the dot diameter decreased. © (2013) Trans Tech Publications, Switzerland.


Hosaka S.,Gunma University | Mohamad Z.,Gunma University | Akahane T.,Gunma University | Yin Y.,Gunma University | And 5 more authors.
Advanced Materials Research | Year: 2012

We have studied the possibility to form fine magnetic column arrays using 30-keV-electron beam (EB) drawing with thin calixarene resist and 200-eV-Ar ion milling, and nanometer-sizing effect of the magnetic column on the corecive force for patterned media. We achieved 20-nm-sized resist dot arrays on PtCo magnetic and thin metals layers on glass substrate. We formed fine magnetic column arrays with a diameter of 39 to 106 nm and a space of about 100 nm using the resist pattern by the 200-eV Ar ion-milling. Using the nano magnetic column arrays, the hysteresis were measured by X-ray magnetic circular dichroism (XMCD) with an energy of 11.57 keV, which corresponds to an energy edge of Pt-L3. It is clarified that a coercive force of the nanometer-sized magnetic column increased as the diameter decreased. © (2012) Trans Tech Publications, Switzerland.


Honda N.,Tohoku Institute of Technology | Yamakawa K.,Research Institute of Advanced Technology | Ouchi K.,Research Institute of Advanced Technology
IEEE Transactions on Magnetics | Year: 2010

Recording properties of bit patterned media with weakly inclined anisotropy were studied by simulation. When a shielded planar head was used, a recording system with an areal density of 2.6 Tbit/in2 was expected for 30-degree inclined anisotropy media. Relatively large tolerance of around 4% in the anisotropy field and 7 degrees in orientation dispersion as well as write margins in down- and cross-track directions would be expected. Recording densities would be extended to 4 Tbit/in2 with additional exchange coupling between the dots. It is expected that bit patterned media with weakly inclined anisotropy is one of promising media for ultra high density recording. © 2006 IEEE.


Honda N.,Tohoku Institute of Technology | Yamakawa K.,Research Institute of Advanced Technology | Ariake J.,Research Institute of Advanced Technology | Kondo Y.,Research Institute of Advanced Technology | Ouchi K.,Research Institute of Advanced Technology
IEEE Transactions on Magnetics | Year: 2011

Bit patterned media with inclined anisotropy were proposed along with media design with a higher saturation magnetization and a small thickness for the dot. Inclination of the anisotropy axis was found to reduce broadened switching field distribution of the media caused by the magnetostatic interaction between the dots. Recording simulation at an areal density of 2.6 Tbit/in2 using a write field of a shielded planar head exhibited substantially increased write shift margins of 6.5 nm and 10 nm in down- and cross track directions, respectively, for the media with inclined anisotropy when the anisotropy dispersion of the media was as small as 2%. Recording density was expected to be increased beyond 4 Tbit/in2 for the media with additional exchange coupling between the dots. © 2006 IEEE.


Wang Y.,Lanzhou University | Wang Y.,Akita University | Ariake J.,Research Institute of Advanced Technology | Wang T.,Lanzhou University | And 6 more authors.
Journal of Applied Physics | Year: 2010

Exchange coupled composite media Co- TiO2 /Pt/CoPt- TiO 2 were studied in terms of structures and magnetic properties. In these media exchange coupled grains with soft-grain/interlayer/hard-grain structure are successfully formed although the Pt interlayers were undoped. Based on that ECC structure, Co- TiO2 soft layers with higher saturation magnetization were found to be more useful to reduce the interlayer thickness for the optimal exchange coupling state and also the total thickness of the medium. Meanwhile, the sensitivity of coercivity on the interlayer thickness can also be decreased. On the other hand, the Pt interlayer induced interface anisotropy and strengthend intergranular exchange coupling; therefore, improved coercivities (Pt thickness less than 0.5 nm) and thermal stability were observed. © 2010 American Institute of Physics.


Kim S.-J.,Jeju National University | Kim S.-J.,Research Institute of Advanced Technology
Journal of Applied Physics | Year: 2011

A coupled stacked Josephson junctions (SJJs) with completely perforated holes of 0.2 m 0.4 m in high-Tc superconducting Bi2Sr 2CaCu2O8d (Bi-2212) were fabricated using a 3D focused ion beam etching method. We investigated external field angle i dependence of junction resistance Rj at various magnetic fields and temperatures. When a constant external magnetic fields He value of 1 T and a bias current Ib value of 1 A were applied to the sample with changing external field angle i, unspecified equidistant and periodic peak structures in the SJJs were induced. The periodic peaks of Rj shows the resistive switching transition from zero resistance state to resistance state. © 2011 American Institute of Physics.


Saini S.,Jeju National University | Kim G.S.,Jeju National University | Kim S.-J.,Research Institute of Advanced Technology
Journal of Superconductivity and Novel Magnetism | Year: 2010

To study the detailed characteristics of a nano-periodic Josephson junction array in a Bi 2Sr 2Ca 2Cu 3O 10+δ (Bi-2223) single crystal whisker without shunted grain boundaries, we fabricate a submicron stack with an area of 0.5 μm × 0.5 μm and height of approximately 200 nm using a focused ion beam (FIB) etching technique. The stack has several hundreds of elementary Josephson junctions along the c-axis. We fabricate the stack by rotation and tilt of the sample stage in the FIB. The current-voltage (I-V) characteristics give a well-defined superconducting gap (V g) and we notice suppression of the critical current in submicron junction with respect to big sized junction. We believe that the suppression of critical current in submicron junction is due to the normal resistance of the junction which belongs to the quantum resistance range. © Springer Science+Business Media, LLC 2010.


Uno K.,Ibaraki University | Ono T.,Ibaraki University | Shimizu I.,Research Institute of Advanced Technology
Optics Communications | Year: 2011

The analytical form for the reconstructed field of a hologram illuminated by a reference beam coded with a multicolored aperture array filter is derived. Experiments showed that the colored aperture array filter improved the quality of the reconstructed image by reducing the intensity of crosstalk images. Some parameters of the aperture array configuration that influence image quality were investigated. This technique presented here can be applied to full-color holographic displays and dot matrix holographic printers, etc. © 2010 Elsevier B.V. All rights reserved.

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