The paper studies the spatial variation of the magnetization in a nonconducting magnetic sample with an excess number of magnons in comparison to the equilibrium. The phenomenon is considered using the Landau-Lifshits equation with additional terms describing the longitudinal relaxation of the magnetization, the magnon diffusion and the magnon creation by external pumping. The free energy of the system is presented in the mean field approximation. It is shown that, if the pumping exceeds some critical value, regions of the new phase arise where the magnetic moments are oriented opposite to the magnetization of the magnetic sample. The phenomenon is similar to the appearance of droplets of the condensed phase in the supersaturated vapor. The appearance of the new phase either in the form of a single domain or a periodical lattice is demonstrated. The studied process is a competitor to the process of the Bose-Einstein condensation of magnons.
Thickness-dependent magnon spin transport in antiferromagnetic insulators: Crossover from quasi-three-dimensional to quasi-two-dimensional regimes
Norwegian University of Science and Technology（挪威科技大学）；Eindhoven University of Technology（埃因霍温理工大学）；ENSTA, Institut Polytechnique de Paris（巴黎理工学院 ENSTA）
Recently it was discovered that van der Waals-bonded magnetic materials retain long range magnetic ordering down to a single layer, opening many avenues in fundamental physics and potential applications of these fascinating materials. One such material is FePS3, a large spin (S=2) Mott insulator where the Fe atoms form a honeycomb lattice. In the bulk, FePS3 has been shown to be a quasi-two-dimensional-Ising antiferromagnet, with additional features in the Raman spectra emerging below the Neel temperature of approximately 120 K. Using magneto-Raman spectroscopy as an optical probe of magnetic …
The recent emergence of 2D van der Waals magnets down to atomic layer thickness provides an exciting platform for exploring quantum magnetism and spintronics applications. The van der Waals nature stabilizes the long-range ferromagnetic order as a result of magnetic anisotropy. Furthermore, giant tunneling magnetoresistance and electrical control of magnetism have been reported. However, the potential of 2D van der Waals magnets for magnonics, magnon-based spintronics, has not been explored yet. Here, we report the experimental observation of long-distance magnon transport in quasi-twodimensio…
We explore spin dynamics in Cu(1,3-bdc), a quasi-2D topological magnon insulator. The results show that the thermal evolution of Landé $g$-factor ($g$) is anisotropic: $g_\textrm{in-plane}$ reduces while $g_\textrm{out-plane}$ increases with increasing temperature $T$. Moreover, the anisotropy of the $g$-factor ($Δg$) and the anisotropy of saturation magnetization ($ΔM_\textrm{s}$) are correlated below 4 K, but they diverge above 4 K. We show that the electronic orbital moment contributes to the $g$ anisotropy at lower $T$, while the topological orbital moment induced by thermally excited spin…
Terahertz driven magnetization dynamics are explored in the orthoferrite DyFeO3. A high-field, single cycle THz pulse is used to excite magnon modes in the crystal together with other resonances. Both quasi-ferromagnetic and quasi-antiferromagnetic magnon modes are excited and appear in time-resolved measurements of the Faraday rotation. Other modes are also observed in the measurements of the time-resolved linear birefringence. Analysis of the excitation process reveals that despite larger than expected electro-optical susceptibility it is mainly the THz magnetic field that couples to the qua…
Emergence of multiple quasi-ferromagnetic magnon modes induced by strong magnetoelastic coupling in $TmFeO_3$ single crystal
Johannes Gutenberg University Mainz（约翰内斯·古腾堡美因茨大学）；Shanghai University（上海大学）；Shanghai Jiao Tong University（上海交通大学）；Norwegian University of Science and Technology（挪威科技大学）
The recent isolation of two-dimensional (2D) magnets offers tantalizing opportunities for spintronics and magnonics at the limit of miniaturization. One of the key advantages of atomically-thin materials is their outstanding deformation capacity, which provides an exciting avenue to control their properties by strain engineering. Herein, we investigate the magnetic properties, magnon dispersion and spin dynamics of the air-stable 2D magnetic semiconductor CrSBr ($T_C$ = 146 K) under mechanical strain using first-principles calculations. Our results provide a deep microscopic analysis of the co…
CuCrO2 is a manifestation of a two-dimensional triangular antiferromagnet which exhibits an incommensurate noncollinear magnetic structure similar to a classical 120 degree ordering. Using the inelastic neutron scattering technique, direct evidence of a magnon-phonon coupling in CuCrO2 is revealed via the mixed magnon-phonon character of the excitation mode at 12.5 meV as well as a minimum at the zone boundary. A simple model Hamiltonian that incorporates an exchange striction type magnon-phonon coupling reproduces the observed features accurately. Also, continuum excitations originating from …
Magnon-polarons are coherently mixed quasiparticles that originate from the strong magnetoelastic coupling of lattice vibrations and spin waves in magnetic-ordered materials. Recently, magnon-polarons have attracted a lot of attention since they provide a powerful tool to manipulate magnons, which is essential for magnon-based spintronic devices. In this work, we report the experimental observation of facet-dependent magnon-polarons in epitaxial ferrimagnetic Fe3O4 thin films via spin Seebeck effect measurement. The critical magnetic fields for the magnon-polarons in the (110)- and (100)-orien…
Magnetic anisotropy from interligand hopping in strongly correlated insulators: application to the magnon spectrum of CrI$_3$
RIKEN Center for Emergent Matter Science (CEMS)（RIKEN 新兴物质科学中心）；Zernike Institute for Advanced Materials, University of Groningen（格罗宁根大学泽尼克先进材料研究所）；CNR-SPIN Institute for Superconducting and other Innovative Materials and Devices（CNR-SPIN 超导及其他创新材料与器件研究所）
