Research Achievements - Original paper -

Investigation of Substitution of Nickel Cations in Cobalt Ferrite (CoFe<inf>2</inf>O<inf>4</inf>) Nanoparticles and Their Influence on Frequency and Temperature Dependent Dielectric and Magnetodielectric Properties

B. Dash, K. L. Routray, S. Saha, S. Yoshimura, S. Ratha, M. K. Rout

Transactions on Electrical and Electronic Materials ( Transactions on Electrical and Electronic Materials )  25 ( 2 ) 232 - 246   2024.03  [Refereed]

Research paper (journal)   International Co-author

DOI

Structural, magnetic and dielectric properties of green synthesized Ag doped NiFe<inf>2</inf>O<inf>4</inf> spinel ferrite

Sunirmal Saha, Krutika Routray, Pritish. Hota, Biswajita Dash, Satoru Yoshimura, Soumyaranjan Ratha, and Traibhab Kumar Nayak

Journal of Molecular Structure ( Journal of Molecular Structure )  1302   2024.03  [Refereed]

Research paper (journal)   International Co-author

DOI

Optimizing the reactive ion etching conditions with minimal damage for high functional magnetic nano device application in BiFeO<inf>3</inf>-based thin film by Eu/Co substitution

S. Ratha, G. Egawa, S. Yoshimura

Applied Surface Science ( Applied Surface Science )  643   158704   2024.01  [Refereed]

Research paper (journal)   Domestic Co-author

DOI

Investigation of Fabrication Conditions and Acceleration of Crystallization of α"-Fe₁₆N₂ Thin Film Fabricated by Pulsed DC Reactive Sputtering for High Density Magnetic Recording Media Application

Ikuko KATSUYAMA, Genta EGAWA, Satoru YOSHIMURA

Journal of the Society of Materials Engineering for Resources of Japan ( The Society of Materials Engineering for Resources of JAPAN )  34 ( 0 ) 6 - 14   2024.01  [Refereed]

Research paper (journal)   Domestic Co-author

DOI CiNii Research

Analysis of substitution of bismuth cations in CoFe<inf>2</inf>O<inf>4</inf> nanoparticles and their influence on frequency and temperature-dependent dielectric and magnetodielectric properties

Biswajita Dash, Sunirmal Saha, Satoru Yoshimura, Soumyaranjan Ratha, and Jashashree Ray

Journal of Materials Science: Materials in Electronics ( Journal of Materials Science: Materials in Electronics )  34 ( 36 )   2023.12  [Refereed]

Research paper (journal)   International Co-author

DOI

Magnetization reversal of [Co/Pd] perpendicular magnetic thin film dot on (Bi,La)(Fe,Co)O<inf>3</inf>multiferroic thin film by applying electric field

Satoru Yoshimura, Naoya Oshita, Genta Egawa, and Munusamy Kuppan

Nanotechnology ( Nanotechnology )  34 ( 46 ) 465703   2023.08  [Refereed]  [Invited]

Research paper (journal)   Domestic Co-author

DOI

Synergistic Effect of Allium-like Ni9S8 & Cu7S4 Electrodeposited on Nickel Foam for Enhanced Water Splitting Activity

M. Mottakin, V. Selvanathan, Md. A. Islam, H. Almohamadi, N. H. Alharthi, S. Yoshimura, Md. Akhtaruzzaman

Chemistry - An Asian Journal ( Chemistry - An Asian Journal )    e202300532   2023.08  [Refereed]

Research paper (journal)   International Co-author

DOI

Excellent magnetic properties in multiferroic BiFeO3 based thin films for magnetic devices application

Soumyaranjan Ratha, Munusamy Kuppan, Genta Egawa, Satoru Yoshimura

Nano-Structures & Nano-Objects ( Elsevier )  35   101007   2023.07  [Refereed]

Research paper (journal)   Domestic Co-author

DOI

Facile electrodeposition of biphasic CuSx/CoSx nanostructures as bifunctional electrocatalysts for seawater splitting

M. Mottakin, Vidhya Selvanathan, Syaza Amira Razali, Md. Ariful Islam, Hamad Almohamadi, Nabeel H. Alharthi, Satoru Yoshimura, Md. Akhtaruzzaman

Electrochimica Acta ( Elsevier )  463   142861   2023.07  [Refereed]

Research paper (journal)   International Co-author

DOI

Effects of substituted elements and amounts of B-site on magnetic properties of ferromagnetic and ferroelectric (Bi,La)(Fe1-yMy)O3 (M=Ni,Co) thin films

SUZUKI Yuta, OZEKI Takumi, EGAWA Genta, YOSHIMURA Satoru

Journal of the Society of Materials Engineering for Resources of Japan ( The Society of Materials Engineering for Resources of JAPAN )  33 ( 1_2 ) 12 - 17   2023.04  [Refereed]

Research paper (journal)   Domestic Co-author

CiNii Research

Development of (Bi0.5L 0.5)(Fe0.7Co0.3)O3 (L=La, Nd, Sm, Gd, Dy) Tthin Films with Excellent Magnetic Properties for Magnetic Device Application

S. Ratha, D. Yamamoto, K. Takeda, M. Kuppan, G. Egawa, and S. Yoshimura

International Journal of the Society of Materials Engineering for Resources ( 日本素材物性学会 )  25 ( 2 ) 174 - 178   2022.10  [Refereed]

Research paper (journal)   Domestic Co-author

<p>(Bi_0.5<i>L</i>_0.5)(Fe_0.7Co_0.3)O₃ (<i>L </i>=<i> </i>La, Nd, Sm, Gd, Dy) thin films with ferromagnetism and ferroelectricity were fabricated using pulsed DC sputtering technique to obtain high saturation magnetization, perpendicular magnetic anisotropy and large magnetic Kerr effect. These magnetic properties are very important for realization of high performance magnetic devices driven by electric field. All (Bi_0.5<i>L</i>_0.5)(Fe_0.7Co_0.3)O₃ (<i>L </i>=<i> </i>La, Nd, Sm, Gd, Dy) thin films had relatively high saturation magnetization, perpendicular magnetic anisotropy and magnetic Kerr effect. Especially, (Bi_0.5Nd_0.5)(Fe_0.7Co_0.3)O₃ thin film had a very high saturation magnetization of 140 emu/cm³ (1.40×10⁵ A/m), a high perpendicular magnetic anisotropy of 2.6 at ratio of perpendicular coercivity against in-plane coercivity and (Bi_0.5La_0.5)(Fe_0.7Co_0.3)O₃ thin film had a very high magnetic Kerr rotation angle of 0.72°. These magnetic properties were excellent compared with the case of (Bi_0.5<i>A</i>_0.5)FeO₃ (<i>A </i>=<i> </i>Ca, Sr, Ba) thin films with the maximum value of 90 emu/cm³ (9.0×10⁴ A/m) (for saturation magnetization), 0.8 (for ratio of Perpendicular coercivity against in-plane coercivity) and 0.03° (for magnetic Kerr rotation angle) which were fabricated previously. These magnetic properties are very important for realization of high performance magnetic devices driven by electric field.</p>

DOI CiNii Research

Investigations on Spintronic RFeO₃ Crystals Grown by Optical Floating Zone Technique

P. Ramesh Babu, S. Kalainathan, and S. Yoshimura

International Journal of the Society of Materials Engineering for Resources ( 日本素材物性学会 )  25 ( 2 ) 179 - 182   2022.10  [Refereed]  [Invited]

Research paper (journal)   International Co-author

<p>Magnetic crystals are physically important to know their intrinsic magnetic properties. Magnetic crystals are also technologically important and their creation has aided crystal growth significantly. Rareearth orthoferrites material (RFeO₃) is one of the major components used in manufacturing sophisticated gadgets. This study focuses on the growth and physical properties of the optically generated RFeO₃ (R=Y, Gd and Sm) single crystals. The floating zone method generates single crystals of 3-20 mm/h in the optical zone. The purity of the grown materials was confirmed from the Powder X-Ray Diffraction (PXRD) analysis. The addition of Gd to YFeO₃ increases the lattice parameters of the material. Magnetic properties of the grown crystal were studied between 20-700 K. At high temperature, two anomalous effects were observed, one at (T_SR=480 K) due to spin reorientation and the other is antiferromagnetic (AFM) to paramagnetic transitions at (T_N= 670 K). Bloch parameter was also calculated. Microhardness value decreases nonlinearly. When the applied load is greater than 1.96 N, there is a transition from palmqvist to median crack due to the plastic deformation of the crystal. Controllable magnetic and mechanical characteristics will help to enhance performance of magnetic devices.</p>

DOI CiNii Research

Development of BiFeO3-based multiferroic thin films with large saturation magnetization and perpendicular magnetic anisotropy -The effect of the Co substitution against Fe on magnetic properties-

T. Ozeki, D. Yamamoto, G. Egawa, and S. Yoshimura

Journal of the Magnetics Society of Japan ( 日本磁気学会 )  46 ( 3 ) 64 - 69   2022.05  [Refereed]

Research paper (journal)   Domestic Co-author

<p>  High saturation magnetization and perpendicular magnetic anisotropy are required for ferromagnetic / ferroelectric thin films to apply magnetic recording such as magnetic writing elements of magnetic wire memory, which is a next-generation device with very high recording density. To realize the magnetic properties, substitution of Co against Fe in (Bi_1-xBax)FeO₃ and (Bi_1-xLa_x)FeO₃ thin films were investigated. In the (Bi,Ba)(Fe,Co)O₃ thin films, both Ba and Co substitution up to several tens at% had contribution to increase the saturation magnetization. The high saturation magnetization was obtained in (Bi,Ba)(Fe,Co)O₃ thin films with the total composition of Ba and Co of around 60 at%. Further increment of Ba and Co substitution decreased the saturation magnetization because the formation of the BiFeO₃ phase is hindered by an excess amount of Ba and Co with larger ion radius than Bi and Fe. Co substitution up to 20 at% had contribution to increase the perpendicular magnetic anisotropy. In the (Bi,La)(Fe,Co)O₃ thin films, the effect of La substitution was not large to increase the saturation magnetization and perpendicular magnetic anisotropy, however the effect of Co substitution up to 30 at% was large to increase the saturation magnetization and perpendicular magnetic anisotropy.</p>

DOI CiNii Research

Dependence of magnetic properties in superparamagnetic Co-granular thin films on deposition rate and effectiveness of a new pulsed DC reactive sputtering method for film fabrication with high deposition rate.

KOBAYASHI Takumi, NAKADA Akito, EGAWA Genta, YOSHIMURA Satoru

Journal of the Society of Materials Engineering for Resources of Japan ( The Society of Materials Engineering for Resources of JAPAN )  32 ( 1_2 ) 22 - 27   2022.03  [Refereed]

Research paper (journal)   Domestic Co-author

DOI CiNii Research

Effect of laser-assisted heating and annealing on the crystal structure and magnetic properties of(Bi, <i>A</i>)FeO₃(<i>A</i>=Ca, Sr, Ba(alkaline earth metal)) thin films

SUZUKI Riku, OZEKI Takumi, EGAWA Genta, YOSHIMURA Satoru

Journal of the Society of Materials Engineering for Resources of Japan ( The Society of Materials Engineering for Resources of JAPAN )  32 ( 1_2 ) 15 - 21   2022.03  [Refereed]

Research paper (journal)   Domestic Co-author

DOI CiNii Research

High-resolution alternating magnetic force microscopy using an amorphous FeB-based tip driven by an inverse magnetostrictive effect: imaging of the high-density magnetic recording media

M. V. Makarova, Y. Akaishi, Y. Suzuki, K. S. Rao, S. Yoshimura, H. Saito

Journal of Magnetism and Magnetic Materials ( Journal of Magnetism and Magnetic Materials )  546 ( 10 ) 168755   2022.01  [Refereed]

Research paper (journal)   Domestic Co-author

DOI

Magnetic properties of (Bi1−xLax)(Fe,Co)O3 films fabricated by a pulsed DC reactive sputtering and demonstration of magnetization reversal by electric field

Munusamy Kuppan, Daichi Yamamoto, Genta Egawa, Sivaperuman Kalainathan, Satoru Yoshimura

Scientific Reports ( Scientific Reports )  11   11118-1 - 11118-8   2021.05  [Refereed]

Research paper (journal)   International Co-author

DOI

Guidelines for fabrication of high quality BiFeO₃ based multiferroic thin films in pulsed DC reactive sputtering method

Takeda K., Yamamoto D., Yoshimura S.

Transaction of the Magnetics Society of Japan Special Issues ( The Magnetics Society of Japan )  4 ( 2 ) 116 - 120   2020.09  [Refereed]

Research paper (journal)   Domestic Co-author

<p>  BiFeO₃ based thin films with ferromagnetism were fabricated by using a pulsed DC reactive sputtering method. Guidelines on sputtering targets for fabricating the films are discussed in regard to obtaining high-quality BiFeO₃ based thin films. By using a target with a low oxide content (low molar ratio of oxide) and thus good conductivity, it is possible to suppress the charging and arc discharge on the surface of the target and enable high-energy sputtering. As a result, high-quality BiFeO₃ based thin films with a high saturation magnetization were formed. By using a target with a high oxygen content (including oxides with a high oxidation valence), the generation of oxygen vacancies that degrade the ferroelectric properties is suppressed, and pinning sites that suppress domain wall movement are then also suppressed. As a result, high-quality BiFeO₃ based thin films with good ferromagnetic properties could be formed.</p>

DOI CiNii Research

Alternating Magnetic Force Microscopy: Effect of Si doping on the temporal performance degradation of amorphous FeCoB magnetic tips

Makarova, Y. Akaishi, T. Ikarashi, K. S. Rao, S. Yoshimura, and H. Saito

Journal of Magnetism and Magnetic Materials ( Journal of Magnetism and Magnetic Materials )  471   209 - 214   2019.02  [Refereed]

Research paper (journal)   Domestic Co-author

DOI

High coercivity and resolution FePt•MgO-coated tip for imaging the magnetic field of perpendicular magnetic write head by alternating magnetic force microscopy (A-MFM)

Fu Zheng, Satoru Yoshimura, Shinya Yasui, Genta Egawa, and Hitoshi Saito

Journal of the Magnetics Society of Japan ( Journal of the Magnetics Society of Japan )  43 ( 1 ) 6 - 10   2019.01  [Refereed]

Research paper (journal)   Domestic Co-author

<p>  High coercivity FePt•MgO films were successfully synthetized on cone-shape Si tips in a very high frequency (VHF) plasma irradiation-assisted magnetron sputtering system to prepare the MFM tips for evaluation of the AC magnetic field of perpendicular magnetic write head at high write current. Alloying with MgO significantly enhanced the coercivity of the magnetic coating due to the isolation of FePt grains by MgO. As a result, a high coercivity close to 20 kOe was achieved. The AC magnetic field images of the perpendicular magnetic write head at high write current were taken on alternating MFM (A-MFM) by this tip. A clear amplitude image with a strong signal at the main pole position was observe compared to the pure FePt layer-coated tip, which gave a blurry image and very small amplitude. Fourier analysis of the images obtained by this kind of FePt•MgO tip gives a spatial resolution of about 15 nm in air atmosphere. It is clear that the cone-shape FePt•MgO-coated MFM tip with a coercivity higher than the magnetic field to be measured is effective and capable for measuring the high AC magnetic field for an HD perpendicular magnetic write head at a very high write current.</p>

DOI CiNii Research