Magnetics

Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Every material is influenced to some extent by a magnetic field. The most familiar effect is on permanent magnets, which have persistent magnetic moments caused by ferromagnetism. The prefix ferro- refers to iron, because permanent magnetism was first observed in a form of natural iron ore called magnetite, Fe3O4. Most materials do not have permanent moments. Some are attracted to a magnetic field (paramagnetism); others are repulsed by a magnetic field (diamagnetism); others have a more complex relationship with an applied magnetic field (spin glass behavior and antiferromagnetism). Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. These include copper, aluminium, gases, and plastic. Pure oxygen exhibits magnetic properties when cooled to a liquid state.

The magnetic state (or magnetic phase) of a material depends on temperature and other variables such as pressure and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change.

  • “Bethe Strings” Experimentally Demonstrated as Many-Body Quantum States for the First Time

    In SrCo₂V₂O₈ the cobalt ions (CO²⁺) form in the interior of a chain of edges-linked oxygen octahedra a quasi-one-dimensional electron spin chain with spin S = ½. © Universität Augsburg/IfP/EP V

    The synthesis of quasi one-dimensional magnets and their investigation by means of optical spectroscopy in extremely high magnetic fields led to success. Augsburg /AL/KPP - “Bethe strings” are excitations of strongly bound electron spins in one-dimensional quantum spin systems. These quantum spin states are named after the physicist Hans Bethe, who first described them theoretically in 1931.

  • A better understanding of nanomaterials

     Petascale Simulations of Self-Healing Nanomaterials | by Argonne National Laboratory.

    In the past six years, the National Research Programme “Opportunities and Risks of Nanomaterials” (NRP 64) intensively studied the development, use, behaviour and degradation of engineered nanomaterials, including their impact on humans and on the environment.

    Twenty-three research projects on biomedicine, the environment, energy, construction materials and food demonstrated the enormous potential of engineered nanoparticles for numerous applications in industry and medicine. Thanks to these projects we now know a great deal more about the risks associated with nanomaterials and are therefore able to more accurately determine where and how they can be safely used.

  • A Material with Promising Properties

    Picture of a hybrid particle taken by a transmission electron microscope. Pictured are the inorganic (dark) and organic (light) lamellas that the particle is made of, as well as the tubular shapes (the low-contrast area in the middle). Through vaporisation with Europium, the hybrid stage can be transformed into pure EuO. Copyright: University of Konstanz

    Konstanz scientist synthesises an important ferromagnetic semiconductor. The Collaborative Research Centre CRC 1214 at the University of Konstanz has developed a method for synthesising Europium (II) oxide nanoparticles - a ferromagnetic semiconductor that is relevant for data storage and data transport. Ferromagnetic semiconductors have attracted increasing attention over the last decade. Their properties make them promising functional materials that can be used in the field of spin-based electronics (spintronics). Spintronics is of crucial importance for the storage and transport of information.

  • A Nano-Roundabout for Light

    Functional principle of a nano-roundabout.  © TU Wien

    At TU Wien, it was possible to create a nanoscale optical element that regulates the flow of light particles at the intersection of two glass fibers like a roundabout. A single atom was used to control the light paths. Just like in normal road traffic, crossings are indispensable in optical signal processing. In order to avoid collisions, a clear traffic rule is required. A new method has now been developed at TU Wien to provide such a rule for light signals. For this purpose, the two glass fibers were coupled at their intersection point to an optical resonator, in which the light circulates and behaves as in a roundabout. The direction of circulation is defined by a single atom coupled to the resonator. The atom also ensures that the light always leaves the roundabout at the next exit. This rule is still valid even if the light consists merely of individual photons. Such a roundabout will consequently be installed in integrated optical chips – an important step for optical signal processing.

  • A new spin on electronics

    The spin of electrons transports information in this conducting layer between two isolators. Image: Christoph Hohmann / NIM

    Interface between insulators enables information transport by spin.
    Modern computer technology is based on the transport of electric charge in semiconductors. But this technology’s potential will be reaching its limits in the near future, since the components deployed cannot be miniaturized further. But, there is another option: using an electron’s spin, instead of its charge, to transmit information. A team of scientists from Munich and Kyoto is now demonstrating how this works.

  • An injectable guidance system for nerve cells

    Dr.-Ing. Laura De Laporte and PhD student Jonas Rose analyze the orientation of nerve cells (red) along the paths provided by gel rods (green). J. Hillmer, DWI

    In many tissues of the human body, such as nerve tissue, the spatial organization of cells plays an important role. Nerve cells and their long protrusions assemble into nerve tracts and transport information throughout the body. When such a tissue is injured, an accurate spatial orientation of the cells facilitates the healing process. Scientists from the DWI – Leibniz Institute for Interactive Materials in Aachen developed an injectable gel, which can act as a guidance system for nerve cells. They recently published their results obtained from cell culture experiments in the journal ‚Nano Letters‘.

  • Antiferromagnets Prove their Potential for Spin-Based Information Technology

    Crystal structure of Mn2Au with antiferromagnetically ordered magnetic moments  Ill./©: Libor Šmejkal, JGU

    Physicists at Mainz University demonstrate technologically feasible read-out and writing of digital information in antiferromagnets / Basic principle for ultrafast and stable magnetic memory. Within the emerging field of spin-based electronics, or spintronics, information is typically defined by the orientation of the magnetization of ferromagnets. Researchers have recently been also interested in the utilization of antiferromagnets, which are materials without macroscopic magnetization but with a staggered orientation of their microscopic magnetic moments. Here the information is encoded in the direction of the modulation of the magnetic moments, the so-called Néel vector.

  • Bakterien aus dem Blut «ziehen»

    Bakterien können mit magnetischer Blutreinigung entfernt werden (links). Eine Lösung mit magnetischen Eisenpartikeln (oben rechts), kann mitt einem Magneten "gereinigt" werden (unten rechts). Empa

    Magnete statt Antibiotika, das könnte eine mögliche neue Behandlungsmethode bei Blutvergiftungen sein. Dazu wird das Blut der Patienten mit magnetischen Eisenpartikeln versetzt, die die Bakterien an sich binden, ehe sie durch Magnete aus dem Blut entfernt werden. Erste Laborversuche sind an der Empa in St. Gallen gelungen – und erfolgversprechend. Blutvergiftungen enden auch heutzutage noch in über 50% der Fälle tödlich, lassen sich aber im Anfangsstadium durchaus kurieren. Daher ist oberstes Gebot, schnell zu handeln. Aus diesem Grund verabreichen Ärzte meist schon bei einem Verdacht auf Blutvergiftung Antibiotika, ohne vorher abzuklären, ob es sich tatsächlich um eine bakterielle Sepsis handelt, was wiederum die Gefahr für Resistenzen massiv erhöht. Es gilt also, eine schnelle und effektive Therapie zu finden, möglichst ohne auf Antibiotika zurückgreifen zu müssen.

  • Bit Data Goes Anti-Skyrmions

    Anti-skyrmions on a racetrack. MPI of Microstructure Physics

    Today’s world, rapidly changing because of “big data”, is encapsulated in trillions of tiny magnetic objects – magnetic bits – each of which stores one bit of data in magnetic disk drives. A group of scientists from the Max Planck Institutes in Halle and Dresden have discovered a new kind of magnetic nano-object in a novel material that could serve as a magnetic bit with cloaking properties to make a magnetic disk drive with no moving parts – a Racetrack Memory – a reality in the near future.

  • Blood flow under magnetic magnifier

    Arterial Spin Labeling allows to visualize vascular territories in the brain without the need of contrast agents – one of many applications. © Photo Fraunhofer MEVIS

    A training workshop at Fraunhofer MEVIS will deliver information about the possibilities of perfusion magnetic resonance imaging.

    When diagnosing strokes and heart diseases or looking at tumors, perfusion magnetic resonance imaging offers a gentler way to capture the blood flow circulation in the organs. However, the method is far from being implemented to its full potential at many clinics. The Fraunhofer Institute for Medical Image Computing MEVIS in Bremen, Germany is organizing a workshop entitled “Measurement of Perfusion and Capillary Exchange” from June 21 to 23 to promote adoption of the method. The event will provide information about its applications and the current state of research.

  • Construction Set of Magnon Logic Extended: Magnon Spin Currents Controlled Via Spin Valve Structure

    Depending on the magnetic configuration of the spin valve, the electrical signal is transmitted (bottom) or suppressed (top). ill./©: Joel Cramer

    Magnon spintronics employs magnons instead of electrical charges for information processing. In the emerging field of magnon spintronics, researchers investigate the possibility to transport and process information by means of so-called magnon spin currents. In contrast to electrical currents, on which todays information technology is based, magnon spin currents do not conduct electrical charges but magnetic momenta.

  • Cooling towards absolute zero using super-heavy electrons

    Temperature evolution of an Yb0.81Sc0.19Co2Zn20 single crystal during the reduction of a magnetic field from 8 to 0 Tesla. © University of Augsburg, IFP/EP VI

    New quantum material significantly improves adiabatic demagnetization cooling

  • Defects at the spinterface disrupt transmission

    An organic radical approaches a lattice of rutile crystals (red) – here with an ideal surface free of defects Graphic: Benedetta Casu and Arrigo Calzolari

    Tübingen researchers put metal-oxides and organic magnets together; applications for electronics in sight

  • Eine Mini-Antenne für die Erzeugung von hochfrequenten Spinwellen

    Eine Mini Antenne für die Erzeugung von hochfrequenten Spinwellen | Das Zentrum eines magnetischen Wirbels sendet unter hochfrequenten magnetischen Wechselfeldern Spinwellen mit sehr kurzen Wellenlängen aus. Abbildung: HZDR

    Im Zuge der rasant fortschreitenden Miniaturisierung steht die Datenverarbeitung mit Hilfe elektrischer Ströme vor zum Teil unlösbaren Herausforderungen. Eine vielversprechende Alternative für den Informationstransport in noch kompakteren Chips sind magnetische Spinwellen. Wissenschaftlern des Helmholtz-Zentrums Dresden-Rossendorf (HZDR) ist es nun bei einer internationalen Zusammenarbeit gelungen, Spinwellen mit extrem kurzen Wellenlängen im Nanometer-Bereich – eine entscheidende Eigenschaft für die spätere Anwendung – gezielt zu erzeugen.

  • Electric field shakes a magnet in one trillionth of a sec. Novel method of spin control discovered

    An intense THz pulse (red waveform) changes the electronic orbitals of a magnetic material leading to oscillation of spins (compass needles). Dr. Rostislav Mikhaylovskiy

    An international team of scientists from Germany, the Netherlands and Russia has successfully demonstrated a novel, highly efficient and ultrafast magnetization control scheme by employing electromagnetic waves oscillating at terahertz frequencies. The new concept will be published in the upcoming issue of Nature Photonics.

  • Essential Quantum Computer Component Downsized by Two Orders of Magnitude

    The new nonreciprocal device acts as a roundabout for photons. Here, arrows show the direction of photons propagation. IST Austria/Birgit Rieger

    Researchers at IST Austria have built compact photon directional devices. Their micrometer-scale, nonmagnetic devices route microwave photons and can shield qubits from harmful noise. Qubits, or quantum bits, are the key building blocks that lie at the heart of every quantum computer. In order to perform a computation, signals need to be directed to and from qubits. At the same time, these qubits are extremely sensitive to interference from their environment, and need to be shielded from unwanted signals, in particular from magnetic fields. It is thus a serious problem that the devices built to shield qubits from unwanted signals, known as nonreciprocal devices, are themselves producing magnetic fields.

  • Exotischer Materiezustand: "Flüssige" Quantenspins bei tiefsten Temperaturen beobachtet

    Exotischer Materiezustand Flüssige Quantenspins bei tiefsten Temperaturen beobachtet | Im Kristallgitter von Kalzium-Chrom-Oxid gibt es sowohl ferromagnetische Wechselwirkungen (grüne und rote Balken) als auch antiferromagnetische (blaue Balken). Abbildung: HZB

    Ein Team am HZB hat experimentell eine sogenannte Quanten-Spinflüssigkeit in einem Einkristall aus Kalzium-Chrom-Oxid nachgewiesen. Dabei handelt es sich um einen neuartigen Materiezustand. Das Besondere an dieser Entdeckung: Nach gängigen Vorstellungen war das Quantenphänomen in diesem Material gar nicht möglich. Nun liegt eine Erklärung vor. Die Arbeit erweitert das Verständnis von kondensierter Materie und könnte auch für die zukünftige Entwicklung von Quantencomputern von Bedeutung sein. Die Ergebnisse sind nun in Nature Physics veröffentlicht.

  • Fighting Myocardial Infarction with Nanoparticle Tandems

    Injection: Via a cannula introduced into the infarction area, the cells loaded with magnetic nanoparticles are injected into the damaged heart muscle tissue of the mouse. © Photo: Dr. Annika Ottersbach/Uni Bonn

    How can damaged cardiac tissue following a heart attack best be treated with replacement muscle cells? A research team under the supervision of the University of Bonn is now presenting an innovative method on mice: Muscle replacement cells, which are to take over the function of the damaged tissue, are loaded with magnetic nanoparticles. These cells are then injected into the damaged heart muscle and held in place by a magnet, causing the cells to engraft better onto the existing tissue. The scientists show that this leads to a significant improvement in heart function. The journal "Biomaterials" presents the results in advance online, the print version will be published in the future.

  • Floating Rotors Report for Duty

    Active magnetic bearings (AMB) use electromagnets to magnetically levitate a rotor.

    Siemens has developed Simotics AMB, a new magnetic bearing system for high-power machines with large rotor diameters. The new technology is based on proven standard electronic components. It optimizes the design, maintenance, and operation of machines that rely on huge rotors and integrates data from their bearings into an installation’s IT environment. Without any physical contact, the controlled magnetic fields of a new magnetic bearing system from Siemens keep 10-ton rotors in the middle of their bearings. What’s more, the rotors do not deviate by more than a hair’s breadth from the center even when spinning at maximum speed. Based on active magnetic bearing (AMB) technology, Siemens’ new Simotics AMB system uses tried and tested standard electronic components that are normally used to control electric motors in machine tool applications.

  • Forscher sehen Biomolekülen bei der Arbeit zu

    Ein Cytochrom-Molekül  wurde mit einem magnetischen Etikett versehen (farbige Struktur rechts oben). Zusammen mit einem Bestandteil des Cytochroms (rot) konnte dann der Abstand bestimmt werden. © AG Schiemann/Uni Bonn

    Wissenschaftlern der Universität Bonn ist es gelungen, einem wichtigen Zellprotein bei der Arbeit zuzusehen. Sie nutzten dazu eine Methode, mit der man Strukturänderungen komplexer Moleküle messen kann. Das weiter entwickelte Verfahren erlaubt es, derartige Prozesse in der Zelle zu beobachten, also der natürlichen Umgebung. Die Forscher stellen zudem eine Art Werkzeugkasten zur Verfügung, der die Vermessung unterschiedlichster Moleküle erlaubt. Ihre Studie ist jetzt in der Zeitschrift „Angewandte Chemie International Edition“ erschienen. Wenn wir eine vorweihnachtliche Walnuss öffnen wollen, benutzen wir dazu in der Regel einen Nussknacker. Der besteht im einfachsten Fall aus zwei Schenkeln, die sich um ein Gelenk gegeneinander bewegen und so Druck auf die Schale ausüben können. Ganz simpel, eigentlich – um zu begreifen, wie so ein Nussknacker funktioniert, genügt es uns, ihn ein einziges Mal in Aktion zu sehen.