Scientists report the fabrication of a nonreciprocal optical resonator with a small length footprint of 290 µm on a silicon-on-insulator substrate. The device achieves unidirectional optical transmission with an isolation ratio of up to 19.5 dB near the telecommunications wavelength of 1,550 nm in a homogeneous external magnetic field.

https://udel.edu/~hujuejun/My%20Papers/Journal%20Papers/On-chip%20optical%20isolation%20in%20monolithically%20integrated%20non-reciprocal%20optical%20resonators.pdf

On-chip optical isolation in monolithically integrated non-reciprocal optical resonators

Growth of nm-thick yttrium iron garnet films and ferromagnetic resonance (FMR) linewidth properties in the films are reported. The films were grown on gadolinium gallium garnet substrates by pulsed laser deposition (PLD). Films in the 5–35 nm thickness range showed a (111) orientation and a surface roughness between 0.1 and 0.3 nm. The 10 nm films showed a 10 GHz FMR linewidth of about 6 Oe and a damping constant of 3.2 × 10−4. The FMR linewidth increases with both the surface roughness and the surface Fe deficiency. Thicker films exhibit a smaller FMR linewidth and a lower damping constant.

Growth and ferromagnetic resonance properties of nanometer-thick yttrium iron garnet films

Recent results in magnonics – a topical and rapidly developing branch of spintronics and magnetoelectronics – are presented. The paper describes measurement techniques and theoretical approaches used to explore physical processes associated with the spin-wave propagation in complex nano- and micro-dimensional magnetic structures. The results of the application of magnetic structures in signal processing and transmission systems are discussed. In particular, results on spin wave propagation in distributed magnetic periodic structures, lumped systems, coupled waveguide structures, and controllable magnonic structures are considered. Specific examples of circuitry based on magnonic structures are discussed, and possibilities for further developing this circuitry are explored.

https://iopscience.iop.org/article/10.3367/UFNe.0185.201510m.1099/pdf

Magnonics: a new research area in spintronics and spin wave electronics

Growth of nm-thick yttrium iron garnet (YIG) films by sputtering and ferromagnetic resonance (FMR) properties in the films were studied. The FMR linewidth of the YIG film decreased as the film thickness was increased from several nanometers to about 100 nm. For films with very smooth surfaces, the linewidth increased linearly with frequency. In contrast, for films with big grains on the surface, the linewidth-frequency response was strongly nonlinear. Films in the 7–26 nm thickness range showed a surface roughness between 0.1 nm and 0.4 nm, a 9.48-GHz FMR linewidth in the 6–10 Oe range, and a damping constant of about 0.001.

Ferromagnetic resonance of sputtered yttrium iron garnet nanometer films

Atomically thin ferromagnetic (FM) films were recently prepared by mechanical exfoliation of bulk FM semiconductor ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$. They provide a platform to explore novel two-dimensional (2D) magnetic phenomena, and they offer exciting prospects for new technologies. By performing systematic ab initio density functional calculations, here we study two relativity-induced properties of these 2D materials (monolayer, bilayer, and trilayer as well as bulk), namely magnetic anisotropy energy (MAE) and magneto-optical (MO) effects. Competing contributions of both magnetocrystalline anisotropy energy (C-MAE) and magnetic dipolar anisotropy energy (D-MAE) to the MAE are computed. The calculated MAEs of these materials are large, being on the order of $\ensuremath{\sim}0.1$ meV/Cr. Interestingly, we find that out-of-plane magnetic anisotropy is preferred in all the systems except the monolayer, where in-plane magnetization is favored because here the D-MAE is larger than the C-MAE. Crucially, this explains why long-range FM order was observed in all the few-layer ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ except the monolayer because the out-of-plane magnetic anisotropy would open a spin-wave gap and thus suppress magnetic fluctuations so that long-range FM order could be stabilized at finite temperature. In the visible frequency range, large Kerr rotations up to $\ensuremath{\sim}2.{2}^{\ensuremath{\circ}}$ in these materials are predicted, and they are comparable to that observed in famous MO materials such as PtMnSb and ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. Moreover, they are $\ensuremath{\sim}100$ times larger than that of $3d$ transition metal monolayers deposited on Au surfaces. Faraday rotation angles in these 2D materials are also large, being up to $\ensuremath{\sim}{120}^{\ensuremath{\circ}}/\ensuremath{\mu}\mathrm{m}$, and they are thus comparable to the best-known MO semiconductor ${\mathrm{Bi}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. These findings thus suggest that with large MAE and MO effects, atomically thin ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ films would have potential applications in novel magnetic, MO, and spintronic nanodevices.

Large magneto-optical effects and magnetic anisotropy energy in two-dimensional Cr 2 Ge 2 Te 6

Magneto-optical properties of yttrium iron garnet (YIG) thin films elaborated by radio frequency sputtering

Thin films of Yttrium Iron Garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system on quartz and Gadolinium Gallium Garnet (GGG) for optical applications or alumina substrates for microwave applications. A post deposition annealing is needed to obtain the crystallization of YIG films and the magnetic properties which are correlated with the magneto-optical properties. Their crystallographic, morphologic and magnetic properties are explored. The variation of Faraday rotation is studied versus the wavelength. For both optical substrates, quartz and GGG, results are comparable with the literature for bulk material. A microwave isolator was realized with YIG thin film on alumina substrate in a coplanar configuration. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

YIG thin films for magneto-optical and microwave applications

In this paper, we present the experimental results of a coplanar isolator made on both bulk YIG and thin-film YIG. An external field has been applied on this device and we observe the amplitude of the nonreciprocal effect, which is between 1.8 and 6.2 dB for a resonance frequency of 3.3 and 6.9 GHz for bulk YIG and a nonreciprocal effect of 0.3 dB at 9 GHz for 2.5-μm YIG thin films. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 470–471, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20339

Exploration of a thin YIG film-based coplanar isolator

An issue of current research is the integration of microwave ferrite devices with semiconductor technologies by using vacuum deposition techniques. Thin magnetic films may be used in commercial products and they can be more easily involved in the development of magnetic devices if we are able to extract their magnetic properties. One of the interesting points of this paper is to highlight the properties of a thin film, such as anisotropic behavior to release non reciprocal devices. A study of physicochemical and magnetic properties is tackled and experimental results are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

T. Boudiar

Papers

Magneto-optical properties of yttrium iron garnet (YIG) thin films elaborated by radio frequency sputtering

YIG thin films for magneto-optical and microwave applications

Exploration of a thin YIG film-based coplanar isolator

Microwave characterization of magnetic thin films

Élaboration de couches minces YIG par pulvérisation cathodique RF pour la réalisation de composants hyperfréquences intégrés