An attractive direction in next-generation information processing is the development of systems employing particles or quasiparticles other than electrons--ideally with low dissipation--as information carriers. One such candidate is the magnon: the quasiparticle associated with the eigen-excitations of magnetic materials known as spin waves. The realization of single-chip all-magnon information systems demands the development of circuits in which magnon currents can be manipulated by magnons themselves. Using a magnonic crystal--an artificial magnetic material--to enhance nonlinear magnon-magnon interactions, we have succeeded in the realization of magnon-by-magnon control, and the development of a magnon transistor. We present a proof of concept three-terminal device fabricated from an electrically insulating magnetic material. We demonstrate that the density of magnons flowing from the transistor's source to its drain can be decreased three orders of magnitude by the injection of magnons into the transistor's gate.

/pdf/magnon-transistor-for-all-magnon-data-processing-18dgl5h4h6.pdf

Magnon transistor for all-magnon data processing

Magnons—the quanta of spin waves—propagating in magnetic materials with wavelengths at the nanometer-scale and carrying information in the form of an angular momentum, can be used as data carriers in next-generation, nano-sized low-loss information processing systems. In this respect, artificial magnetic materials with properties periodically varied in space, known as magnonic crystals, are especially promising for controlling and manipulating the magnon currents. In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these crystals. Special attention is devoted to the utilization of magnonic crystals for processing of analog and digital information. Magnonic crystals for data processing 2

https://iopscience.iop.org/article/10.1088/1361-6463/aa6a65/pdf

Magnonic crystals for data processing

Magnetism is a very fascinating and dynamic field Especially in the last 30 years it has experienced many major advances in the full range from novel fundamental phenomena to new products Applications such as hard disk drives and magnetic sensors are part of our daily life, and new applications, such as in non-volatile computer random access memory, are expected to surface shortly Thus it is timely for describing the current status, and current and future challenges in the form of a Roadmap article This 2014 Magnetism Roadmap provides a view on several selected, currently very active innovative developments It consists of 12 sections, each written by an expert in the field and addressing a specific subject, with strong emphasize on future potential This Roadmap cannot cover the entire field We have selected several highly relevant areas without attempting to provide a full review - a future update will have room for more topics The scope covers mostly nano-magnetic phenomena and applications, where surfaces and interfaces provide additional functionality New developments in fundamental topics such as interacting nano-elements, novel magnon-based spintronics concepts, spin-orbit torques and spin-caloric phenomena are addressed New materials, such as organic magnetic materials and permanent magnets are covered New applications are presented such as nano-magnetic logic, non-local and domain-wall based devices, heat-assisted magnetic recording, magnetic random access memory, and applications in biotechnology May the Roadmap serve as a guideline for future emerging research directions in modern magnetism

https://iopscience.iop.org/article/10.1088/0022-3727/47/33/333001/pdf

The 2014 Magnetism Roadmap

Spin waves constitute an important part of research in the field of magnetization dynamics. Spin waves are the elementary excitations of the spin system in a magnetically ordered material state and magnons are their quasi particles. In the following article, we will discuss the optical method of Brillouin light scattering (BLS) spectroscopy which is a now a well established tool for the characterization of spin waves. BLS is the inelastic scattering of light from spin waves and confers several benefits: the ability to map the spin wave intensity distribution with spatial resolution and high sensitivity as well as the potential to simultaneously measure the frequency and the wave vector and, therefore, the dispersion properties. For several decades, the field of spin waves gained huge interest by the scientific community due to its relevance regarding fundamental issues of spindynamics in the field of solid states physics. The ongoing research in recent years has put emphasis on the high potential of spin waves regarding information technology. In the emerging field of \textit{magnonics}, several concepts for a spin-wave based logic have been proposed and realized. Opposed to charge-based schemes in conventional electronics and spintronics, magnons are charge-free currents of angular momentum, and, therefore, less subject to scattering processes that lead to heating and dissipation. This fact is highlighted by the possibility to utilize spin waves as information carriers in electrically insulating materials. These developments have propelled the quest for ways and mechanisms to guide and manipulate spin-wave transport. In particular, a lot of effort is put into the miniaturization of spin-wave waveguides and the excitation of spin waves in structures with sub-micrometer dimensions. For the further development of potential spin-wave-based devices, the ability to directly observe spin-wave propagation with spatial resolution is crucial. As an optical technique BLS do

/pdf/micro-focused-brillouin-light-scattering-imaging-spin-waves-si83g1bzrr.pdf

Micro-focused Brillouin light scattering: imaging spin waves at the nanoscale

Towards Oxide Electronics: a Roadmap

We present an experimental study of spin-wave excitation and propagation in microstructured waveguides consisting of a 100 nm thick yttrium iron garnet/platinum (Pt) bilayer. The life time of the spin waves is found to be more than an order of magnitude higher than in comparably sized metallic structures, despite the fact that the Pt capping enhances the Gilbert damping. Utilizing microfocus Brillouin light scattering spectroscopy, we reveal the spin-wave mode structure for different excitation frequencies. An exponential spin-wave amplitude decay length of 31 μm is observed which is a significant step towards low damping, insulator based micro-magnonics.

Spin-wave excitation and propagation in microstructured waveguides of yttrium iron garnet/Pt bilayers

Liquid phase epitaxy of YBa2Cu3O7−x on NdGaO3 and LaGaO3 substrates

YBa2Cu3O7-δ films were grown by liquid phase epitaxy in Y-ZrO2 crucibles on (110)NdGaO3 substrates. A change in the preferred crystallographic growth direction was observed reproducibly. The growth mode changes from pure c-axis oriented over mixed c/a-axis oriented films to pure a-axis oriented films with increasing undercooling. X-ray diffraction measurements and atomic force microscopy investigations with c-axis oriented as well as a-axis oriented films are presented. It will be shown that atomically smooth steps with 0.2-0.8 μM width can be achieved by LPE, which are free from melt remnants. Furthermore the values for the enthalpy of dissolution from literature, which are varying in a wide range, will be combined and a new value will be calculated in terms of a multi particle model.



YBa2Cu3O7-δ-Schichten wurden mittels Flussigphasenepitaxie auf (110)NdGaO3-Substraten in Y-ZrO2-Tiegeln hergestellt. Es kann reproduzierbar ein Wechsel der bevorzugten kristallographischen Wachstumsrichtung beobachtet werden. Das Wachstum wechselt mit zunehmender Unterkuhlung von rein c-Achsen orientiert uber gemischt c/a-Achsen orientierte Schichten hin zu rein a-Achsen orientierten Schichten. Sowohl von c-Achsen orientierten als auch von a-Achsen orientierten Schichten werden Rontgenbeugungsmessungen und Untersuchungen mittels Atomkraftmikros kopie prasentiert. Es kann gezeigt werden, das mittels LPE atomar glatte Stufenflachen von 0,2–0,8 μM Breite erreicht werden, die frei von Schmelzresten sind. Ferner werden die stark variierenden Werte fur die molare Losungsenthalpie aus der Literatur vereint und ein neuer Wert im Mehrteilchenmodell berechnet.

Liquid Phase Epitaxy (LPE) of YB2Cu3O7-δ High Tc Superconductors

A detailed x‐ray diffraction study is reported for a/b‐axes oriented YBa2Cu3O7−δ films obtained by the liquid phase epitaxy technique. The films were grown epitaxially in the tetragonal state on (110) NdGaO3 substrates so that [001]film∥ [110]subs and [100]film∥ [001]subs, 90°‐[100]/[010] boundaries were almost absent. Below the tetragonal‐to‐orthorhombic transition temperature, the film undergoes intensive {hh0}‐type twinning. The volume of the a‐axis oriented material is similar to that of the b‐axis oriented fraction and the presence of both orientations is likely to be controlled by {hh0}‐type twinning. High temperature diffraction of the substrate indicates that nucleation of YBa2Cu3O7−δ on (110) NdGaO3 takes place on a square two‐dimensional lattice and therefore the observed strong in‐plane alignment is probably controlled by impurity action and/or surface relaxation rather than simple mismatch effects. The difference between the thermal expansion coefficients of the film and the substrate (αfilm[1...

P. Görnert

Papers

Spin-wave excitation and propagation in microstructured waveguides of yttrium iron garnet/Pt bilayers

Liquid phase epitaxy of YBa2Cu3O7−x on NdGaO3 and LaGaO3 substrates

Liquid Phase Epitaxy (LPE) of YB2Cu3O7-δ High Tc Superconductors

X‐ray diffraction studies of the epitaxy of a/b‐axes oriented YBa2Cu3O7−δ films grown by liquid phase epitaxy

On the flux growth and some properties of superconducting YBa2Cu3O7-ϰ single crystals and LPE films