Search

The magnetic resonance of iron garnets is at the heart of rich physics and provides a crucial technology used inside microwave components. A barrier still stands in the way of integrated cryogenic devices with iron garnets, because their epitaxy requires paramagnetic substrates that cause large microwave losses at low temperatures. Finding alternative combinations of substrates and magnetic garnets is thus essential to enabling cryogenic integrated magnonics. With this motivation, we develop a new approach to the synthesis of epitaxial garnet films, based on the co-sputtering of binary oxides, enabling a precise and continuous tuning of the iron garnet composition. By substituting a controlled proportion of the iron with additional yttrium, we obtain Y$_{3}$(Y$_{x}$Fe$_{5-x}$)O$_{12}$ films of high crystalline quality that can be lattice-matched to yttrium scandium gallium garnet (YSGG), a diamagnetic substrate suitable for low-temperature applications. Ferromagnetic resonance performed at low temperatures confirms the elimination of substrate paramagnetism losses on YSGG. We also show that the Y$_{3}$(Y$_{x}$Fe$_{5-x}$)O$_{12}$ system can be matched to other substrates, such as gadolinium yttrium scandium gallium garnet and gadolinium scandium gallium garnet. Additionally, we demonstrate that Bi-substituted films of (Bi$_{0.8}$Y$_{2.2}$)Fe$_{5}$O$_{12}$ also offer ideal lattice matching to YSGG for low-temperature magnetic resonance. The present approach of controlled substitutions in iron garnets to obtain ideal lattice matching with diamagnetic substrates opens a very promising pathway to magnonic devices operating in low-temperature environments., Comment: Main: 18 pages, 6 figures; Supplement: 9 pages, 6 figures

A promising approach to attain long-distance coherent spin propagation is accessing quantum Hall topological spin-polarized edge states in graphene. Achieving this without large external magnetic fields necessitates engineering graphene band structure, obtainable through proximity to 2D magnetic materials. In this work, we detect spin-polarized helical edge transport in graphene at zero external magnetic field, allowed by the out-of-plane magnetic proximity of CrPS$_4$ that spin-splits the zeroth Landau level. This zero-field detection of the quantum anomalous spin Hall state is enabled by large induced spin-orbit and exchange couplings in the graphene that also lead to the detection of an enhanced Berry curvature, shifting the Landau levels, and result in an unconventional sequence of quantum Hall plateaus. Remarkably, we observe that the quantum anomalous Hall transport in the magnetized graphene persists up to room temperature. The detection of spin-polarized helical edge states at zero magnetic field and the robustness of the quantum anomalous Hall transport up to room temperature open the route for practical applications of magnetic graphene in quantum information processing and spintronic circuitries.

In the present work the classical problem of harmonic oscillator in the hyperbolic space $H_2^2$: $z_0^2+z_1^2-z_2^2-z_3^2=R^2$ has been completely solved in framework of Hamilton-Jacobi equation. We have shown that the harmonic oscillator on $H_2^2$, as in the other spaces with constant curvature, is exactly solvable and belongs to the class of maximally superintegrable system. We have proved that all the bounded classical trajectories are closed and periodic. The orbits of motion are ellipses or circles for bounded motion and ultraellipses or equidistant curve for infinite ones.