Article
Physics, Applied
Ahmed L. Elrefai, Keiji Enpuku, Takashi Yoshida
Summary: The alignment of easy axes significantly impacts the magnetization curves and harmonic spectra of magnetic nanoparticles, highlighting its importance in biomedical applications. A distribution function can be used to express the degree of easy axis alignment, aiding in the quantitative evaluation of magnetic nanoparticle performance in biomedical applications.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Zhengrong Li, Zhongwen Ouyang, Jiaojiao Cao, Xiaochen Liu, Tongtong Xiao, Lei Wang, Youyuan Liang, Zhaoming Tian, Zhenxing Wang, Zhengcai Xia
Summary: A new perfect triangular lattice antiferromagnet K2Ni(SeO3)(2) has been synthesized, in which both in-plane and inter-plane geometric frustration is present. The compound shows antiferromagnetic order at T(N) ≈ 7 K. High-field magnetization and electron spin resonance indicate the presence of easy-plane anisotropy. Density functional theory calculations confirm the excellent two-dimensionality of the compound. Thus, K2Ni(SeO3)(2) is a perfect triangular-lattice antiferromagnet with strong frustration and easy-plane anisotropy.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Engineering, Electrical & Electronic
Ahmed L. Elrefai, Teruyoshi Sasayama, Takashi Yoshida, Keiji Enpuku
Summary: The alignment of magnetic easy axes significantly affects the magnetic properties of immobilized MNPs samples, with the influence decreasing as the strength of the ac excitation field increases. These findings are crucial for applications of immobilized MNPs in hyperthermia and magnetic particle imaging.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Materials Science, Multidisciplinary
Keiji Enpuku, Shuya Yamamura, Takashi Yoshida
Summary: The study compares the AC magnetization curves of suspended and immobilized magnetic nanoparticles by changing the excitation field amplitude. It identifies the dominant relaxation mechanisms in suspended samples, with Néel relaxation being prominent at high excitation field and Brownian relaxation contributing more at low field. The research also evaluates the distribution of Néel- and Brownian-dominated MNPs in the samples and discusses the differences in harmonic signals between suspended and immobilized samples.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Hannes Albers, Tobias Knopp, Martin Moeddel, Marija Boberg, Tobias Kluth
Summary: Magnetic nanoparticles (MNPs) are important in biomedical applications such as MRI and MPI. Modeling voltage signals of large ensembles of MNPs in an MPI environment is challenging due to the non-linear magnetization response, leading to time-consuming calibration procedures. Immobilized and oriented MNPs have received attention for encoding the angle of the magnetic easy axis, providing a benchmark system for model-based approaches.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Jongpil Yun, Se Kwon Kim
Summary: The existing proposals for superfluidlike spin transport have been limited to easy-plane magnets, but in this work, we show that superfluidlike spin transport can also be realized based on easy-axis magnets. We find that by applying a spin torque, a nonequilibrium easy-cone state can be engendered in easy-axis magnets, breaking the U(1) spin-rotational symmetry and enabling superfluidlike spin transport. Using micromagnetic simulations, we confirm the theoretical prediction and demonstrate the potential of dynamic states of magnets for studying spin-transport phenomena.
Article
Physics, Applied
Yan-Ting Liu, Yu-Hao Huang, Chao-Chung Huang, Yung-Cheng Li, Chih-Lin Cheng, Chi-Feng Pai
Summary: This article demonstrates a simple measurement method to probe -x spin-orbit-torque (SOT) switching by observing current-driven differential planar Hall signals. The experimental results show that a canted magnetic easy axis engineered by field-annealing processes can generate robust field-free switching effects and further reduce the critical switching current density.
PHYSICAL REVIEW APPLIED
(2022)
Article
Materials Science, Multidisciplinary
Mohd Mawardi Saari, Mohd Herwan Sulaiman, Nurul Akmal Che Lah, Zulkifly Aziz, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada
Summary: This study characterizes the size distribution of magnetic cores in single- and multi-core nanoparticles in water suspension using transmission electron microscopy and static magnetization curve analysis. The magnetic moment distribution suggests a reduction in effective magnetic core size due to magnetization degradation. The AC susceptibility response of MNPs from 5 Hz to 100 kHz is also evaluated to understand the average anisotropy energy ratio.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2021)
Article
Nanoscience & Nanotechnology
Keiji Enpuku, Takashi Yoshida
Summary: Magnetic nanoparticles (MNPs) have been extensively studied for hyperthermia applications. This study investigates the hysteresis loss of immobilized MNPs with partially aligned easy axes and provides analytical expressions for the coercive field and hysteresis loss as functions of the easy-axis angle, beta. The relationship between the loss and the degree of easy-axis alignment is quantitatively clarified.
Article
Chemistry, Physical
R. Caglayan, Y. Mogulkoc, A. Mogulkoc, M. Modarresi, A. N. Rudenko
Summary: In this study, the absorption of F and Cl on ferromagnetic monolayer CrN was investigated using first-principles calculations. It was found that the magnetic properties of CrN can be altered after the adsorption of F and Cl, opening a route to the detection of these gases using magnetic or optical measurements.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
M. Rivero, A. Serrano, J. A. Rodriguez-Velamazan, A. Munoz-Bonilla, J. Sanchez-Marcos
Summary: In this study, a series of zinc ferrite nanoparticles with an average size of 11 nm were successfully synthesized using an electrochemical method in aqueous medium, and their structures and magnetic properties were extensively characterized. The synthetic method allows for control over the size, shape, and composition of the nanoparticles to obtain ferrite nanoparticles with tuneable magnetic properties. The results indicate that the Zn2+ cations in the crystalline spinel structure cause a gradual decrease in the magnetic moments of the ferrites with increasing Zn content, due to the breakdown of super-exchange interactions.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Physics, Applied
Martin Moeddel, Florian Griese, Tobias Kluth, Tobias Knopp
Summary: Advancements in micromachinery and nanotechnology, such as magnetically actuated microrobots for navigating in viscous environments, play a crucial role in medicine. Studies have shown that the spatial orientation of immobilized nanoparticles with parallel-aligned magnetic easy axes affects the magnetization response to an external dynamic magnetic field. This study introduces a method to estimate this orientation and experimentally investigate potential application scenarios.
PHYSICAL REVIEW APPLIED
(2021)
Article
Materials Science, Multidisciplinary
Keiji Enpuku, Yi Sun, Haochen Zhang, Takashi Yoshida
Summary: We studied the harmonic signals caused by the nonlinear AC magnetization curve of suspended magnetic nanoparticles (MNPs) in solution. Numerical simulations were performed to investigate the dominant relaxation in the AC M-H curve affected by Brownian and Ne'el relaxations. The changes in MNP's behavior from Brownian-dominant to Ne'el-dominant relaxation with increased excitation field amplitude were highlighted. Analytical expressions for the third harmonic signal in both dominant cases were obtained.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Physics, Applied
Ajit Kumar Sahoo, J. Mohanty
Summary: The study investigates the chiral spin structures and Néel-type skyrmions in the TbCo/GdFe-based amorphous ferrimagnetic system, showing that skyrmionic configurations are stabilized with the help of dipolar interactions. Optimized thicknesses of TbCo and GdFe layers demonstrate isolated skyrmions with a variety of chiral textures observed in a wide thickness range of ferrimagnetic bilayer systems.
JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM
(2021)
Article
Chemistry, Physical
Lubos Nagy, Adriana Zelenakova, Pavol Hrubovcak, Michael Barutiak, Maksym Lisnichuk, Jozef Bednarcik, Jana Vargova, Rastislav Jendzelovsky, Juraj Sevc, Stefan Vilcek
Summary: Fine CoFe2O4 nanoparticles with citric acid capping were synthesized under different pH conditions. Lower pH led to the formation of a thicker citric acid shell and weaker inter-particle interactions, while higher pH resulted in a thinner organic coating and stronger interactions, leading to the formation of larger agglomerates with pomegranate-like structure.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Ahmed L. Elrefai, Takashi Yoshida, Keiji Enpuku
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2019)
Article
Physics, Applied
Shohei Hamanaga, Takashi Yoshida, Teruyoshi Sasayama, Ahmed L. Elrefai, Keiji Enpuku
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Engineering, Electrical & Electronic
Wataru Yoshimura, Teruyoshi Sasayama, Keiji Enpuku
IEEE TRANSACTIONS ON MAGNETICS
(2019)
Article
Engineering, Electrical & Electronic
Keiji Enpuku, Masaaki Matsuo, Yujiro Yoshida, Shigeya Yamashita, Teruyoshi Sasayama, Takashi Yoshida
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2019)
Article
Physics, Applied
Zhongzhou Du, Yi Sun, Oji Higashi, Keiji Enpuku, Takashi Yoshida
JAPANESE JOURNAL OF APPLIED PHYSICS
(2019)
Article
Physics, Applied
Zhongzhou Du, Yi Sun, Oji Higashi, Yuki Noguchi, Keiji Enpuku, Sebastian Draack, Klaas-Julian Janssen, Tamara Kahmann, Jing Zhong, Thilo Viereck, Frank Ludwig, Takashi Yoshida
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Keiji Enpuku, Ahmed L. Elrefai, Takashi Yoshida, Tamara Kahmann, Jing Zhong, Thilo Viereck, Frank Ludwig
JOURNAL OF APPLIED PHYSICS
(2020)
Article
Engineering, Electrical & Electronic
Ahmed L. Elrefai, Teruyoshi Sasayama, Takashi Yoshida, Keiji Enpuku
Summary: The alignment of magnetic easy axes significantly affects the magnetic properties of immobilized MNPs samples, with the influence decreasing as the strength of the ac excitation field increases. These findings are crucial for applications of immobilized MNPs in hyperthermia and magnetic particle imaging.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Physics, Applied
Ahmed L. Elrefai, Keiji Enpuku, Takashi Yoshida
Summary: The alignment of easy axes significantly impacts the magnetization curves and harmonic spectra of magnetic nanoparticles, highlighting its importance in biomedical applications. A distribution function can be used to express the degree of easy axis alignment, aiding in the quantitative evaluation of magnetic nanoparticle performance in biomedical applications.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Keiji Enpuku, Takashi Yoshida
Summary: A new analytical expression for hysteresis loss of magnetic nanoparticles (MNPs) has been obtained through numerical simulation, which is applicable to a wide range of MNP parameters and excitation conditions, showing an optimization method for hyperthermia application. Quantitative study on how MNP parameters and excitation conditions affect the hysteresis loss was demonstrated, with a numerical example reaching a loss as large as 1 kW/g Fe. The results will be useful for hyperthermia application.
Article
Nanoscience & Nanotechnology
Keiji Enpuku, Takashi Yoshida
Summary: Magnetic nanoparticles (MNPs) have been extensively studied for hyperthermia applications. This study investigates the hysteresis loss of immobilized MNPs with partially aligned easy axes and provides analytical expressions for the coercive field and hysteresis loss as functions of the easy-axis angle, beta. The relationship between the loss and the degree of easy-axis alignment is quantitatively clarified.
