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Article ; Online: Understanding magnetocrystalline anisotropy based on orbital and quadrupole moments.

Miura, Yoshio / Okabayashi, Jun

Journal of physics. Condensed matter : an Institute of Physics journal

2022 Volume 34, Issue 47

Abstract: Understanding magnetocrystalline anisotropy (MCA) is fundamentally important for developing novel magnetic materials. Therefore, clarifying the relationship between MCA and local physical quantities observed by spectroscopic measurements, such as the ... ...

Abstract	Understanding magnetocrystalline anisotropy (MCA) is fundamentally important for developing novel magnetic materials. Therefore, clarifying the relationship between MCA and local physical quantities observed by spectroscopic measurements, such as the orbital and quadrupole moments, is necessary. In this review, we discuss MCA and the distortion effects in magnetic materials with transition metals (TMs) based on the orbital and quadrupole moments, which are related to the spin-conserving and spin-flip terms in the second-order perturbation calculations, respectively. We revealed that orbital moment stabilized the spin moment in the direction of the larger orbital moment, while the quadrupole moment stabilized the spin moment along the longitudinal direction of the spin-density distribution. The MCA of the magnetic materials with TMs and their interfaces can be determined from the competition between these two contributions. We showed that the perpendicular MCA of the face-centered cubic Ni with tensile tetragonal distortion arose from the orbital moment anisotropy, whereas that of Mn-Ga alloys originated from the quadrupole moment of spin density. In contrast, in the Co/Pd(111) multilayer and Fe/MgO(001), both the orbital moment anisotropy and quadrupole moment of spin density at the interfaces contributed to the perpendicular MCA. Understanding the MCA of magnetic materials and interfaces based on orbital and quadrupole moments is essential to design MCA of novel magnetic applications.
Language	English
Publishing date	2022-10-05
Publishing country	England
Document type	Journal Article ; Review
ZDB-ID	1472968-4
ISSN	1361-648X ; 0953-8984
ISSN (online)	1361-648X
ISSN	0953-8984
DOI	10.1088/1361-648X/ac943f
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Intrinsic Magnetic Proximity Effect at the Atomically Sharp Interface of Co

Nodo, Shoto / Yamane, Ichiro / Suzuki, Motohiro / Okabayashi, Jun / Yokokura, Seiya / Shimada, Toshihiro / Nagahama, Taro

ACS omega

2023 Volume 8, Issue 28, Page(s) 24875–24882

Abstract: ... ...

Abstract	Co
Language	English
Publishing date	2023-07-04
Publishing country	United States
Document type	Journal Article
ISSN	2470-1343
ISSN (online)	2470-1343
DOI	10.1021/acsomega.3c00935
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Understanding voltage-controlled magnetic anisotropy effect at Co/oxide interface.

Nozaki, Tomohiro / Okabayashi, Jun / Tamaru, Shingo / Konoto, Makoto / Nozaki, Takayuki / Yuasa, Shinji

Scientific reports

2023 Volume 13, Issue 1, Page(s) 10640

Abstract: The voltage-controlled magnetic anisotropy (VCMA) effect is a key to realising high-speed, ultralow-power consumption spintronic devices. The fcc-Co-(111)-based stack is a promising candidate for the achievement of large VCMA coefficients. However, only ... ...

Abstract	The voltage-controlled magnetic anisotropy (VCMA) effect is a key to realising high-speed, ultralow-power consumption spintronic devices. The fcc-Co-(111)-based stack is a promising candidate for the achievement of large VCMA coefficients. However, only a few studies on the fcc-Co-(111)-based stack have been reported and the VCMA effect has not been well understood. Previously, we observed a significant increase in the voltage-controlled coercivity (VCC) in the Pt/Ru/Co/CoO/TiO
MeSH term(s)	Anisotropy ; Physical Phenomena ; Diffusion ; Oxides ; Magnetic Phenomena
Chemical Substances	Oxides
Language	English
Publishing date	2023-06-30
Publishing country	England
Document type	Journal Article
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-023-37422-4
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Book ; Online: Tracing magnetic atom diffusion with annealing at the interface between CoMn alloy and MnGa layer by X-ray magnetic circular dichroism

Okabayashi, Jun / Suzuki, Kazuya Z. / Mizukami, Shigemi

2022

Abstract: The magnetic atom diffusion at the interface between CoMn alloy and MnGa layer with annealing is studied using x-ray magnetic circular dichroism (XMCD) analysis. We found that the spins in bcc CoMn are coupled parallel to those in perpendicularly ... ...

Abstract	The magnetic atom diffusion at the interface between CoMn alloy and MnGa layer with annealing is studied using x-ray magnetic circular dichroism (XMCD) analysis. We found that the spins in bcc CoMn are coupled parallel to those in perpendicularly magnetized MnGa layer under the as-grown conditions, while the post-annealing modulates the interfacial magnetic coupling to antiferromagnetic in Co. The element-specific hysteresis curves at each absorption edge revealed the large coercive fields in Mn and Co through the exchange coupling with MnGa. After the annealing process, the changes of XMCD spectral line shapes are related to the interfacial reactions promoting the formation of Mn and Co2MnGa layers, which is deduced from the analysis of transmission electron microscopy. The interfacial diffusion of Mn atoms modulates the magnetic exchange coupling between Mn and Co sites and reverses the direction of perpendicular magnetization. Comment: 12 pages including 3 figures
Keywords	Condensed Matter - Materials Science
Subject code	530
Publishing date	2022-11-09
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Alternative Route Triggering Multistep Spin Crossover with Hysteresis in an Iron(II) Family Mediated by Flexible Anion Ordering.

Hagiwara, Hiroaki / Minoura, Ryo / Udagawa, Taro / Mibu, Ko / Okabayashi, Jun

Inorganic chemistry

2020 Volume 59, Issue 14, Page(s) 9866–9880

Abstract: Multistep spin crossover (SCO) compounds have attracted much attention, since they can be great candidates for high-density multinary memory devices. The introduction of substituents, such as methyl (Me), chloro (Cl), bromo (Br), and methoxy (MeO) groups, ...

Abstract	Multistep spin crossover (SCO) compounds have attracted much attention, since they can be great candidates for high-density multinary memory devices. The introduction of substituents, such as methyl (Me), chloro (Cl), bromo (Br), and methoxy (MeO) groups, at para positions to the phenyl-substituted tripodal N
Language	English
Publishing date	2020-06-26
Publishing country	United States
Document type	Journal Article
ZDB-ID	1484438-2
ISSN	1520-510X ; 0020-1669
ISSN (online)	1520-510X
ISSN	0020-1669
DOI	10.1021/acs.inorgchem.0c01069
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Article ; Online: Cyclic Heterometallic Interactions formed from a Flexible Tripeptide Complex Showing Effective Antiferromagnetic Spin Coupling.

Miyake, Ryosuke / Suganuma, Eri / Kimura, Shun / Mori, Hirotoshi / Okabayashi, Jun / Kusamoto, Tetsuro

Angewandte Chemie (International ed. in English)

2021 Volume 60, Issue 10, Page(s) 5179–5183

Abstract: Developing tunable motifs for heterometallic interactions should be beneficial for fabricating functional materials based on cooperative electronic communications between metal centers. Reported here is the efficient formation of cyclic heterometallic ... ...

Abstract	Developing tunable motifs for heterometallic interactions should be beneficial for fabricating functional materials based on cooperative electronic communications between metal centers. Reported here is the efficient formation of cyclic heterometallic interactions from a complex containing an artificial tripeptide with metal binding sites on its main chain and side chains. X-ray structural analysis and X-ray absorption spectroscopy revealed that the cyclic metal-metal arrangements arise from the amide groups connecting four square-planar Cu
Language	English
Publishing date	2021-01-18
Publishing country	Germany
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2011836-3
ISSN	1521-3773 ; 1433-7851
ISSN (online)	1521-3773
ISSN	1433-7851
DOI	10.1002/anie.202013373
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Article ; Online: Anatomy of interfacial spin-orbit coupling in Co/Pd multilayers using X-ray magnetic circular dichroism and first-principles calculations.

Okabayashi, Jun / Miura, Yoshio / Munekata, Hiro

Scientific reports

2018 Volume 8, Issue 1, Page(s) 8303

Abstract: Element-specific orbital magnetic moments and their anisotropies in perpendicularly magnetised Co/Pd multilayers are investigated using Co L-edge and Pd M-edge angle-dependent x-ray magnetic circular dichroism. We show that the orbital magnetic moments ... ...

Abstract	Element-specific orbital magnetic moments and their anisotropies in perpendicularly magnetised Co/Pd multilayers are investigated using Co L-edge and Pd M-edge angle-dependent x-ray magnetic circular dichroism. We show that the orbital magnetic moments in Co are anisotropic, whereas those in Pd are isotropic. The first-principles density-functional-theory calculations also suggest that the Co/Pd interfacial orbital magnetic moments in Co are anisotropic and contribute to the perpendicular magnetic anisotropy (PMA), and that the isotropic ones in Pd manipulates the Co orbitals at the interface through proximity effects. Orbital-resolved anatomy of Co/Pd interfaces reveals that the orbital moment anisotropy in Co and spin-flipped transition related to the magnetic dipoles in Pd are essential for the appearance of PMA.
Language	English
Publishing date	2018-05-29
Publishing country	England
Document type	Journal Article
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-018-26195-w
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Book ; Online: Origin of Perpendicular Magnetic Anisotropy in Co$_x$Fe$_{3-x}$O$_{4+\delta}$ Thin Films Studied by X-ray Magnetic Circular and Linear Dichroisms

Okabayashi, Jun / Tanaka, Masaaki A. / Morishita, Masaya / Yanagihara, Hideto / Mibu, Ko

2022

Abstract: We investigate the element-specific spin and orbital states and their roles on magnetic anisotropy in the Co-ferrite (Co$_x$Fe$_{3-x}$O$_{4+\delta}$ (001)) thin films which exhibit perpendicular magnetic anisotropy (PMA). The origin of PMA in the low $x$ ...

Abstract	We investigate the element-specific spin and orbital states and their roles on magnetic anisotropy in the Co-ferrite (Co$_x$Fe$_{3-x}$O$_{4+\delta}$ (001)) thin films which exhibit perpendicular magnetic anisotropy (PMA). The origin of PMA in the low $x$ region ($x$ $<$ 1) can be mainly explained by the large perpendicular orbital magnetic moments in the Co$^{2+}$ (3$d^7$) states detected by X-ray magnetic circular and linear dichroisms (XMCD/XMLD). The XMLD for a PMA film ($x=0.2$) with square hysteresis curve shows the oblate charge distribution in the Co$^{2+}$ site, which is consistent with the change in local nearest neighbor distance in Co detected by extended X-ray absorption fine structure analysis. Our finding reveals that the microscopic origin of PMA in Co-ferrite comes from the enhanced orbital magnetic moments along out-of-plane [001] direction through in-plane charge distribution by tensile strain, which adds the material functionalities in spinel ferrite thin films from the viewpoint of strain and orbital magnetic moments. Comment: 11 pages including 4 figures
Keywords	Condensed Matter - Materials Science
Subject code	530
Publishing date	2022-03-30
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys.

Okabayashi, Jun / Miura, Yoshio / Kota, Yohei / Z Suzuki, Kazuya / Sakuma, Akimasa / Mizukami, Shigemi

Scientific reports

2020 Volume 10, Issue 1, Page(s) 9744

Abstract: Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have ... ...

Abstract	Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have never been reported. Here, the origin of PMA in ferrimagnetic Mn
Language	English
Publishing date	2020-06-16
Publishing country	England
Document type	Journal Article
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-020-66432-9
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Book ; Online: Control of conductivity in Fe-rich cobalt-ferrite thin films with perpendicular magnetic anisotropy

Morishita, Masaya / Ichikawa, Tomoyuki / Tanaka, Masaaki A. / Furuta, Motoharu / Mashimo, Daisuke / Honda, Syuta / Okabayashi, Jun / Mibu, Ko

2023

Abstract: We fabricated two types of cobalt-ferrite (001) thin films, insulative Fe-rich cobalt-ferrite CoxFe3-xO4+{\delta} (I-CFO) and conductive Fe-rich cobalt-ferrite CoyFe3-yO4 (C-CFO), with perpendicular magnetic anisotropy (PMA) on MgO (001) substrates. ... ...

Abstract	We fabricated two types of cobalt-ferrite (001) thin films, insulative Fe-rich cobalt-ferrite CoxFe3-xO4+{\delta} (I-CFO) and conductive Fe-rich cobalt-ferrite CoyFe3-yO4 (C-CFO), with perpendicular magnetic anisotropy (PMA) on MgO (001) substrates. Although the stoichiometric cobalt-ferrite is known as an insulating material, it is found that the conductivity of Fe-rich cobalt-ferrites can be controlled by changing the source materials and deposition conditions in the pulsed laser deposition technique. The I-CFO and C-CFO films exhibit PMA through the in-plane lattice distortion. We investigated the Fe-ion-specific valence states in both I-CFO and C-CFO films by M\"ossbauer spectroscopy and X-ray magnetic circular dichroism, and found that the difference in conductivity corresponds to the abundance ratio of Fe2+ state at the octahedral B-site (Oh) in the inverse spinel structure. Furthermore, first-principles calculations reproduce the changes in the density of states at the Fermi level depending on the cation vacancies at the B-site, which explains the difference in the conductivity between I-CFO and C-CFO. Comment: 21 pages including 8 figures
Keywords	Condensed Matter - Materials Science
Subject code	530
Publishing date	2023-04-19
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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