scholarly journals Large Dzyaloshinskii-Moriya interaction induced by chemisorbed oxygen on a ferromagnet surface

2020 ◽  
Vol 6 (33) ◽  
pp. eaba4924 ◽  
Author(s):  
Gong Chen ◽  
Arantzazu Mascaraque ◽  
Hongying Jia ◽  
Bernd Zimmermann ◽  
MacCallum Robertson ◽  
...  
Keyword(s):  
Room Temperature ◽  
Ferromagnetic Layer ◽  
Spin Orbit Coupling ◽  
Winding Number ◽  
Large Magnitude ◽  
Chemisorbed Oxygen ◽  
Magnetic Layers ◽  
Oxygen Coverage ◽  
Opening Up ◽  
Moriya Interaction

The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange interaction that stabilizes chiral spin textures. It is induced by inversion symmetry breaking in noncentrosymmetric lattices or at interfaces. Recently, interfacial DMI has been found in magnetic layers adjacent to transition metals due to the spin-orbit coupling and at interfaces with graphene due to the Rashba effect. We report direct observation of strong DMI induced by chemisorption of oxygen on a ferromagnetic layer at room temperature. The sign of this DMI and its unexpectedly large magnitude—despite the low atomic number of oxygen—are derived by examining the oxygen coverage–dependent evolution of magnetic chirality. We find that DMI at the oxygen/ferromagnet interface is comparable to those at ferromagnet/transition metal interfaces; it has enabled direct tailoring of skyrmion’s winding number at room temperature via oxygen chemisorption. This result extends the understanding of the DMI, opening up opportunities for the chemisorption-related design of spin-orbitronic devices.

Clustering-Triggered Efficient Room Temperature Phosphorescence from Nonconventional Luminophores

2019 ◽  
Author(s):  
Shuyuan Zheng ◽  
Taiping Hu ◽  
Xin Bin ◽  
Yunzhong Wang ◽  
Yuanping Yi ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Efficiency ◽  
Spin Orbit Coupling ◽  
Design Rationale ◽  
Emission Mechanism ◽  
Room Temperature Phosphorescence ◽  
Electronic Interactions ◽  
Energy Gaps ◽  
Theoretical Results

Pure organic room temperature phosphorescence (RTP) and luminescence from nonconventional luminophores have gained increasing attention. However, it remains challenging to achieve efficient RTP from unorthodox luminophores, on account of the unsophisticated understanding of the emission mechanism. Here we propose a strategy to realize efficient RTP in nonconventional luminophores through incorporation of lone pairs together with clustering and effective electronic interactions. The former promotes spin-orbit coupling and boost the consequent intersystem crossing, whereas the latter narrows energy gaps and stabilizes the triplets, thus synergistically affording remarkable RTP. Experimental and theoretical results of urea and its derivatives verify the design rationale. Remarkably, RTP from thiourea solids with unprecedentedly high efficiency of up to 24.5% is obtained. Further control experiments testify the crucial role of through-space delocalization on the emission. These results would spur the future fabrication of nonconventional phosphors, and moreover should advance understanding of the underlying emission mechanism.<br>

scholarly journals Dzyaloshinskii–Moriya interaction in noncentrosymmetric superlattices

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Woo Seung Ham ◽  
Abdul-Muizz Pradipto ◽  
Kay Yakushiji ◽  
Kwangsu Kim ◽  
Sonny H. Rhim ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Degrees Of Freedom ◽  
Orbit Coupling ◽  
Inversion Symmetry ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Band Formation ◽  
Research Activities ◽  
Moriya Interaction

AbstractDzyaloshinskii–Moriya interaction (DMI) is considered as one of the most important energies for specific chiral textures such as magnetic skyrmions. The keys of generating DMI are the absence of structural inversion symmetry and exchange energy with spin–orbit coupling. Therefore, a vast majority of research activities about DMI are mainly limited to heavy metal/ferromagnet bilayer systems, only focusing on their interfaces. Here, we report an asymmetric band formation in a superlattices (SL) which arises from inversion symmetry breaking in stacking order of atomic layers, implying the role of bulk-like contribution. Such bulk DMI is more than 300% larger than simple sum of interfacial contribution. Moreover, the asymmetric band is largely affected by strong spin–orbit coupling, showing crucial role of a heavy metal even in the non-interfacial origin of DMI. Our work provides more degrees of freedom to design chiral magnets for spintronics applications.

scholarly journals Ruderman–Kittel–Kasuya–Yosida-type interfacial Dzyaloshinskii–Moriya interaction in heavy metal/ferromagnet heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Taehyun Kim ◽  
In Ho Cha ◽  
Yong Jin Kim ◽  
Gyu Won Kim ◽  
Andrey Stashkevich ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Exchange Coupling ◽  
Spin Orbit Coupling ◽  
Conduction Electrons ◽  
Indirect Exchange ◽  
Metal Atoms ◽  
Technological Potential ◽  
Interfacial Modification ◽  
Coupling Phenomena ◽  
Moriya Interaction

AbstractThe manipulation of magnetization with interfacial modification using various spin-orbit coupling phenomena has been recently revisited due to its scientific and technological potential for next-generation memory devices. Herein, we experimentally and theoretically demonstrate the interfacial Dzyaloshinskii–Moriya interaction characteristics penetrating through a MgO dielectric layer inserted between the Pt and CoFeSiB. The inserted MgO layer seems to function as a chiral exchange interaction mediator of the interfacial Dzyaloshinskii–Moriya interaction from the heavy metal atoms to ferromagnet ones. The potential physical mechanism of the anti-symmetric exchange is based on the tunneling-like behavior of conduction electrons through the semi-conductor-like ultrathin MgO. Such behavior can be correlated with the oscillations of the indirect exchange coupling of the Ruderman–Kittel–Kasuya–Yosida type. From the theoretical demonstration, we could provide approximate estimation and show qualitative trends peculiar to the system under investigation.

scholarly journals Nonreciprocal charge transport up to room temperature in bulk Rashba semiconductor α-GeTe

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yan Li ◽  
Yang Li ◽  
Peng Li ◽  
Bin Fang ◽  
Xu Yang ◽  
...  
Keyword(s):  
Charge Transport ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Ferromagnetic Layer ◽  
Spin Splitting ◽  
New Paradigm ◽  
Rashba Spin ◽  
Rashba Spin Splitting ◽  
Fundamental Insight ◽  
Insight Into

AbstractNonmagnetic Rashba systems with broken inversion symmetry are expected to exhibit nonreciprocal charge transport, a new paradigm of unidirectional magnetoresistance in the absence of ferromagnetic layer. So far, most work on nonreciprocal transport has been solely limited to cryogenic temperatures, which is a major obstacle for exploiting the room-temperature two-terminal devices based on such a nonreciprocal response. Here, we report a nonreciprocal charge transport behavior up to room temperature in semiconductor α-GeTe with coexisting the surface and bulk Rashba states. The combination of the band structure measurements and theoretical calculations strongly suggest that the nonreciprocal response is ascribed to the giant bulk Rashba spin splitting rather than the surface Rashba states. Remarkably, we find that the magnitude of the nonreciprocal response shows an unexpected non-monotonical dependence on temperature. The extended theoretical model based on the second-order spin–orbit coupled magnetotransport enables us to establish the correlation between the nonlinear magnetoresistance and the spin textures in the Rashba system. Our findings offer significant fundamental insight into the physics underlying the nonreciprocity and may pave a route for future rectification devices.

The EPR Zero-Field Splitting D and its Pressure and Temperature Dependence for Trigonal Mn2+ Centers in [Zn(H2O)6](BF4)2:Mn2+ Crystal

2006 ◽  
Vol 61 (5-6) ◽  
pp. 289-292 ◽  
Author(s):  
Hong-Gang Liu ◽  
Xiao-Xuan Wu ◽  
Wen-Chen Zheng ◽  
Lv He
Keyword(s):  
Temperature Dependence ◽  
Room Temperature ◽  
Coupling Mechanism ◽  
Zero Field ◽  
Spin Orbit Coupling ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Thermal Expansion Coefficients ◽  
Perturbation Formula ◽  
Expansion Coefficients

The EPR zero-field splitting D (= b02 ) and its pressure and temperature dependence for trigonal Mn2+ centers in low and room temperature phases in [Zn(H2O)6](BF4)2 :Mn2+ crystal are studied by a high-order perturbation formula based on the dominant spin-orbit coupling mechanism. From the studies, the local trigonal distortion angles, the local angular compressibilities and the local angular thermal expansion coefficients for Mn2+ centers in both phases of the [Zn(H2O)6](BF4)2 crystal are estimated. The results are discussed

Giant Dzyaloshinskii-Moriya Interaction and Room-Temperature Nanoscale Skyrmions in CoFeB/MgO Heterostructures

2021 ◽  
Author(s):  
Runze Chen ◽  
Xinran Wang ◽  
Houyi Cheng ◽  
Kyu-Joon Lee ◽  
Danrong Xiong ◽  
...  
Keyword(s):  
Room Temperature ◽  
Moriya Interaction

Observation of an Exponential FeSi Spacer Thickness Dependence of the Antiferromagnetic Exchange Coupling in Fe/Si-Based Multilayers

1997 ◽  
Vol 475 ◽  
Author(s):  
J.T. Kohlhepp ◽  
J.J. De Vries ◽  
F.J.A. Den Broeder ◽  
R. Coehoorn ◽  
R.M. Jungblut ◽  
...  
Keyword(s):  
Exchange Coupling ◽  
Room Temperature ◽  
Decay Length ◽  
Antiferromagnetic Exchange ◽  
Interlayer Exchange Coupling ◽  
Magnetic Layers ◽  
Magnetic Analysis ◽  
Spacer Thickness ◽  
Interlayer Exchange ◽  
B2 Structure

ABSTRACTThe magnetic interlayer exchange coupling in Fe/Si-based thin film structures employing sputtered multilayers with variations of Si-alloyed Fe for the magnetic layers and Fe-alloyed Si spacers, as well as wedge-shaped MBE-grown Fe/Si/Fe sandwich samples has been systematically studied. From structural and magnetic analysis it is concluded that ultrathin Si and FexSi100-x (x < 50) spacer layers transform into a crystalline iron suicide with a composition close to Fe50Si50. The exchange coupling mediated by this metallic suicide is antiferromagnetic and depends on the spacer thickness in an exponential, i.e. non-oscillatory, manner with a universial characteristic decay length of 3–4 Å at room temperature. This observation can be qualitatively explained within the framework of a recent coupling theory on the premise that the FeSi interlayer has the metastable CsCl(B2)-structure.

scholarly journals Physical and Topological Properties of Circular DNA

1966 ◽  
Vol 49 (6) ◽  
pp. 103-125 ◽  
Author(s):  
Jerome Vinograd ◽  
Jacob Lebowitz'
Keyword(s):  
Room Temperature ◽  
Melting Behavior ◽  
Neutral Salt ◽  
Winding Number ◽  
Complementary Strand ◽  
Circular Dna ◽  
Tumor Viruses ◽  
Weakly Closed ◽  
A Site ◽  
Melting Experiments

Several types of circular DNA molecules are now known. These are classified as single-stranded rings, covalently closed duplex rings, and weakly bonded duplex rings containing an interruption in one or both strands. Single rings are exemplified by the viral DNA from ϕX174 bacteriophage. Duplex rings appear to exist in a twisted configuration in neutral salt solutions at room temperature. Examples of such molecules are the DNA's from the papova group of tumor viruses and certain intracellular forms of ϕX and λ-DNA. These DNA's have several common properties which derive from the topological requirement that the winding number in such molecules is invariant. They sediment abnormally rapidly in alkaline (denaturing) solvents because of the topological barrier to unwinding. For the same basic reason these DNA's are thermodynamically more stable than the strand separable DNA's in thermal and alkaline melting experiments. The introduction of one single strand scission has a profound effect on the properties of closed circular duplex DNA's. In neutral solutions a scission appears to generate a swivel in the complementary strand at a site in the helix opposite to the scission. The twists are then released and a slower sedimenting, weakly closed circular duplex is formed. Such circular duplexes exhibit normal melting behavior, and in alkali dissociate to form circular and linear single strands which sediment at different velocities. Weakly closed circular duplexes containing an interruption in each strand are formed by intramolecular cyclization of viral λ-DNA. A third kind of weakly closed circular duplex is formed by reannealing single strands derived from circularly permuted T2 DNA. These reconstituted duplexes again contain an interruption in each strand though not necessarily regularly spaced with respect to each other.

scholarly journals Giant Dzyaloshinskii-Moriya interaction in Rashba superlattices

2020 ◽  
Author(s):  
Woo-Seung Ham ◽  
Abdul-Muizz Pradipto ◽  
Kay Yakushiji ◽  
Kwangsu Kim ◽  
Sonny Rhim ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Material Design ◽  
Orbit Coupling ◽  
Inversion Symmetry ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Band Formation ◽  
Stacking Order ◽  
Magnetic Skyrmions ◽  
Moriya Interaction

Abstract Dzyaloshinskii-Moriya interaction (DMI) is considered as one of the most important energy for specific chiral texture such as magnetic skyrmions. The key of generating DMI is absence of structural inversion symmetry and exchange energy with spin-orbit coupling. Therefore, a vast majority of researches about DMI is mainly limited to heavy metal/ferromagnet bilayer systems, only focusing on their interfaces. Here, we report that asymmetric band formation in an artificial superlattice arises from inversion symmetry breaking in stacking order of atomic layers, resulting in bulk DMI. Such bulk DMI is more than 300% larger than simple sum of interfacial contribution. Moreover, the asymmetric band is largely affected by strong spin-orbit coupling, showing crucial role of a heavy metal even in the non-interfacial origin of DMI. Such Rashba superlattices can be a new class of material design for spintronics applications.

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