Spin excitations in ultrathin metallic films
Final Report Abstract
We have quantified the symmetric Heisenberg (HE) as well as the antisymmetric Dzyaloshinskii– Moriya (DM) exchange interaction at the Fe/Ir(111) interface, with C3v symmetry. The pattern of both HE and DM interaction was found to be complex, with a significant antiferromagnetic component. In addition, we provided direct experimental evidence that in layered ferromagnets DM interaction can be tailored via quantum engineering of the lattice symmetry, direct intra- and interlayer DM coupling. We reported on a giant DM interaction in epitaxial Co/Fe bilayers grown on W(110), exhibiting C2v symmetry. The results pave the way of tailoring DM interaction on the atomic length-scales with the perspective of designing desired topological spin textures e.g., skyrmions and antiskyrmions in such structures. We provided quantitative results on the temperature-induced damping and discuss the possible mechanisms. A careful investigation of physical quantities determining the magnons’ propagation indicates that terahertz magnons sustain their propagating character even at temperatures far above the transition temperature. We introduced a new approach of materials design for terahertz magnonics making use of quantum confinement of terahertz magnons in layered ferromagnets. We showed that in atomically designed multilayers composed of alternating atomic layers of ferromagnetic metals one can efficiently excite different magnon modes associated with the quantum confinement in the third dimension i.e., the direction perpendicular to the layers. We showed that these magnon modes possess nonlinear decay rates. We demonstrated experimentally that the magnonic band structure of these systems can be tuned by changing the materials combination and the number of atomic layers, and thereby, realized the first atomic-scale magnonic crystal. Moreover, we demonstrated that the magnonic surface or interface states may show peculiar features, including “standing” or “ultrafast” states. These states can drastically change the electronic and magnonic transport properties of layered structures. In this way one can design layered ferromagnets which act as magnon conductor, semiconductor and insulator of specific states.
Publications
- Group velocity engineering of confined ultrafast magnons, Phys. Rev. Lett. 119, 267201 (2017)
Y.-J. Chen, Kh. Zakeri, A. Ernst, H. J. Qin, Y. Meng and J. Kirschner
(See online at https://doi.org/10.1103/PhysRevLett.119.267201) - Probing of the interfacial Heisenberg and Dzyaloshinskii-Moriya exchange interaction by magnon spectroscopy, J. Phys.: Condens. Matter 29, 013001 (2017)
Kh. Zakeri
(See online at https://doi.org/10.1088/0953-8984/29/1/013001) - Temperature dependence of magnetic excitations: Terahertz magnons above the Curie temperature, Phys. Rev. Lett. 118, 127203 (2017)
H. J. Qin, Kh. Zakeri, A. Ernst and J. Kirschner
(See online at https://doi.org/10.1103/PhysRevLett.118.127203) - Spin waves in disordered materials. J. Phys.: Condens. Matter 30, 423001 (2018)
P. Buczek, S. Thomas, A. Marmodoro, N. Buczek, X. Zubizarreta, M. Hoffmann, T. Balashov, W. Wulfhekel, Kh. Zakeri and A. Ernst
(See online at https://doi.org/10.1088/1361-648X/aadefb) - Terahertz magnonics: Feasibility of using terahertz magnons for information processing, Physica C 549, 164 (2018)
Kh. Zakeri
(See online at https://doi.org/10.1016/j.physc.2018.02.035) - Experimental realization of atomic-scale magnonic crystals, Phys. Rev. Lett. 123, 257202 (2019).
H. J. Qin, S. Tsurkan, A. Ernst and Kh. Zakeri
(See online at https://doi.org/10.1103/PhysRevLett.123.257202) - Discovery of a Giant DMI in systems with additional structural asymmetry, Phys. Rev. B 101, 024409 (2020)
S. Abdizadeh, J. Abouie and Kh. Zakeri
(See online at https://doi.org/10.1103/PhysRevB.101.024409) - Giant Dzyaloshinskii–Moriya interaction in epitaxial Co/Fe bilayers with C2v symmetry. Phys. Rev. B 102, 060406(R) (2020)
S. Tsurkan and Kh. Zakeri
(See online at https://doi.org/10.1103/PhysRevB.102.060406) - Magnonic crystals: Towards terahertz frequencies, J. Phys.: Condens. Matter 32, 363001 (2020)
Kh. Zakeri
(See online at https://doi.org/10.1088/1361-648X/ab88f2) - Unconventional magnonic surface and interface states in layered ferromagnets, Communications Physics 4, 18 (2021)
Kh. Zakeri, H.J. Qin and A. Ernst
(See online at https://doi.org/10.1038/s42005-021-00521-7)
