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Nanostructured Hybrid Magnetic Materials
Published in Ram K. Gupta, Sanjay R. Mishra, Tuan Anh Nguyen, Fundamentals of Low Dimensional Magnets, 2023
Although the graphene shows a weak SOC effect, the graphene on Co films can significantly improve the PMA up to twice that of pristine Co films [25]. The scale of the PMA linearly increases as a function of heterostructure thickness. This provides the possibility for graphene/FM in novel spintronic devices that simultaneously satisfy longer relaxation length and larger PMA than FM metal/oxide or FM metal/NM metal. Recently, chiral magnetism has been observed for graphene/ferromagnetic metal interfaces. This is a shocked and exciting phenomenon for graphene-based spintronics. The chiral magnetism is usually induced by the interfacial Dzyaloshinskii-Moriya interaction (DMI). However, the DMI at the graphene/FM interface has been thought to be weak since the DMI scales with the SOC and the graphene has weak SOC. Significant DMI was achieved at the graphene-ferromagnetic metal interfaces [26]. Notably, the DMI can be significantly improved with more NiCoGr layers.
Spin Waves in Thin Films and Magnonic Crystals with Dzyaloshinskii–Moriya Interactions
Published in Gianluca Gubbiotti, Three-Dimensional Magnonics, 2019
Rodolfo A. Gallardo, David Cortés-Ortuño, Roberto E. Troncoso, Pedro Landeros
In the late fifties of the past century, Dzyaloshinskii proposed in a seminal paper a phenomenological theory of antisymmetric exchange coupling between spins to explain the phenomenon of weak ferromagnetism in antiferromagnetic compounds [1]. Two years later, Moriya derived this interaction as a spin–orbit coupling between electrons within the framework of superexchange theory [2–4]. It was then shown that this anisotropic exchange interaction arises in materials that lack inversion symmetry and where strong spin–orbit coupling effects are present. Nowadays, this antisymmetric exchange coupling is known as the Dzyaloshinskii–Moriya interaction (DMI) and has been a key ingredient for the description of the magnetic properties of a variety of compounds with broken symmetry [5–10]. These include noncentrosymmetric bulk ferromagnets, multiferroics, perovskites, cuprates, and ferromagnetic thin films [11–16], among others. The study of materials with DMIs has been pursued with high interest because it has been thoroughly established, both by theory and experiment, that DMIs induce chiral, topological, and nonreciprocal features. A primary consequence is the occurrence of chiral spin textures such as magnetic helices, skyrmions, skyrmion lattices, and chiral domain walls (DWs) in ferromagnetic materials [17–42].
Spin Waves on Spin Structures: Topology, Localization, and Nonreciprocity
Published in Sergej O. Demokritov, Spin Wave Confinement, 2017
Robert L. Stamps, Joo-Von Kim, Felipe Garcia-Sanchez, Pablo Borys, Gianluca Gubbiotti, Yue Li, Robert E. Camley
Challenges addressed in this field pertain to issues related with spin wave dissipation, device miniaturization [82], and fabrication of artificial magnonic crystals [48–50]. Most recently, consequences of the Dzyaloshinskii-Moriya interaction (DMI) on spin wave properties has been studied extensively, especially in regards to interface-induced DMI. The DMI arises in low-symmetry materials with a strong spin-orbit coupling and is modeled as an antisymmetric form of the exchange interaction. Dzyaloshinskii first postulated this interaction in order to explain weak ferromagnetism in antiferromagnets [26]. A few years later Moriya calculated the second-order energy terms associated with spin-orbit couplings for the exchange interaction, thereby establishing a mechanism for the interaction [68,69].
Recent advances in two-dimensional ferromagnetism: strain-, doping-, structural- and electric field-engineering toward spintronic applications
Published in Science and Technology of Advanced Materials, 2022
Sheng Yu, Junyu Tang, Yu Wang, Feixiang Xu, Xiaoguang Li, Xinzhong Wang
Multiple efforts have been devoted to the electric-field control of magnetism in 2D monolayers. Deng et al. [66] showed that, via ionic gating, the induced extreme charge carriers can strengthen the itinerant ferromagnetism and dramatically elevates Tc of single-layer Fe3GeTe2 above room temperature. The gate voltage can also significantly modulate the coercive field. The ferromagnetic transition temperature Tc was extracted in virtue of anomalous Hall effect measurement (Figure 6(a–g)). Wang et al. [124] showed that, via using ionic liquid and solid Si gating technology, the bipolar field effect transistor based on ferromagnetic insulating Cr2Ge2Te6 thin film exhibited a doping-dependent magnetism. The magneto-optical Kerr measurements demonstrated the significantly reduced saturation field and larger magnetic moment with the elevated gate voltage below the Curie temperature. Liu et al. [125] observed that the Neel-type magnetic Skyrmion spin configurations become energetic-favorable than ferromagnetic spin states as a result of applying out-of-plane electric field by breaking the inversion symmetry and inducing nontrivial Dzyaloshinskii–Moriya interaction.
Strain effect on physical properties of the multiferroic Mn3Sn material: a first-principles calculations
Published in Philosophical Magazine, 2022
W. Bazine, N. Tahiri, O. El Bounagui, H. Ez-Zahraouy
The values of the Mn magnetic moment calculated for the different ways are shown in Figure 3. The calculated value of the magnetic moment indicates that the addition of a layer increases the value of the magnetic moment. Also, the compression of the lattice parameter leads to increases of the Mn Magnetic moment opposite of expansion which decreases the moment. The obtained magnetic moment value is in good agreement compared to the experimental studies [25]. We began the discussions by the magnetic ground states. Three types of magnetic configurations have been considered, one ferromagnetic state, frustrated AFM (see Figure 4), and four Antiferromagnetic states. The Frustrated AFM configurations are found to be the magnetic ground state with the lowest energy among the other magnetic configurations. On the other hand, the favourable magnetic structure obtained energetically is due to the existence of electric Dzyaloshinskii–Moriya interactions, see Figures 4 and 5. The magnetic Dzyaloshinskii–Moriya interaction (DM) occurring from the spin-orbit coupling between Si and Sj pairs of dipole moments via HDM = Dij⋅ (Si× Sj) [25], by taking account of noncollinear magnetism (e.g, magnetic topological defects such as skyrmions, vortices, merons, as well as spin-orbit torques, and magnetically driven ferroelectricity).