Phys.org August 6, 2020 Electrical control of magnetism in van der Waals ferromagnetic semiconductors is an important step in creating novel spintronic devices capable of processing and storing information. Using an electric double-layer transistor device, an international team of researchers (Singapore, UK, China) discovered that the magnetism of a magnetic semiconductor, Cr2Ge2Te6, shows exceptionally strong response to applied electric fields. With electric fields applied, the material was found to exhibit ferromagnetism at temperatures up to 200 K (-73°C). At such temperatures, ferromagnetic order is normally absent in this material. Their analysis suggests that heavy doping promotes a double-exchange mechanism that […]
Tag Archives: Materials science
Scientists discover new class of semiconducting entropy-stabilized materials
Science Daily July 31, 2020 Almost all entropy-stabilized materials so far are either conducting metals or insulating ceramics. Researchers at the University of Michigan have experimentally synthesized and characterized a new class of the multicationic and -anionic entropy-stabilized chalcogenide alloys based on the (Ge,Sn,Pb)(S,Se,Te) formula. The configurational entropy from the disorder of both the anion and the cation sublattices reaches a record value for the equimolar composition and stabilizes the single-phase solid solution. Theoretical calculations and experiments both show that the synthesized alloys are thermodynamically stable at the growth temperature and kinetically metastable at room temperature. Doping and electronic transport […]
‘Fool’s gold’ may be valuable after all
Phys.org July 30, 2020 Magnetoionic devices either electrically tune a known ferromagnet or electrically induce ferromagnetism from another magnetic state which is a limitation for practical use. A team of researchers in the US (University of Minnesota, Augsburg University) took the non-magnetic iron sulfide material and put it in a device in contact with an ionic solution. When they applied as little as 1 volt positively charged molecules were moved to the interface between the electrolyte and iron sulfide, and induced magnetism. Importantly, they were able to turn off the voltage and return the material to its non-magnetic state. The […]
Magnetic nanoparticles change their magnetic structure in a magnetic field
Nanowerk July 27, 2020 Up to now, scientists assumed that magnetism in a nanoparticle is essentially limited to this core area. Using neutron scattering on cobalt ferrite nanoparticles an international team or researchers (France, Germany, Czech Republic) has shown that the applied magnetic field causes some of the previously disordered magnetic moments in the surface region to become aligned, and thus ordered in a way comparable to the magnetization in the core region. However, a residual area with differently aligned spins remains on the surface, which cannot be ordered by the applied magnetic field. Overall, the research showed that the […]
Physics team observes extremely fast electronic changes in real time in a special material class
Phys.org July 7, 2020 Topologically protected Weyl semimetal phase in the transition metal dichalcogenide Td-WTe2 can be controlled and, ultimately, destroyed upon the coherent excitation of an interlayer shear mode. An international team of researchers (Germany, China) provide direct experimental evidence that the shear mode acts on the electronic states near the phase-defining Weyl points. They observed a periodic reduction in the spin splitting of bands. Comparison with higher-frequency coherent phonon modes finally proved the shear mode-selectivity of the observed changes in the electronic structure. findings reveal direct experimental insights into electronic processes that are of vital importance for a […]
New quantum materials with unique properties
Nanowerk June 23, 2020 Researchers in Germany are working on a German Research Foundation funded project that focuses on novel physical phenomena of solids resulting from a particularly strong coupling between a material’s elastic properties and its electronic quantum phases. Based on the findings obtained, the researchers expect to produce new quantum materials with extraordinary properties and open the application potential resulting from interactions between mechanical and electronic properties…read more.
A new platform to stretch 2D materials
Nanowerk June 17, 2020 As the electronic and optical properties of 2D materials can be controlled by mechanical deformations of their crystal structure, strain engineering can be used to modify their electronic properties. Researchers in Spain have developed thermal strain actuators on top of polypropylene substrates to control the biaxial strain in atomically thin MoS2 layers. The actuators can reach a maximum biaxial strain of 0.64 % and reliably modulated at frequencies up to 8 Hz. The strain levels can be varied all the way from 0% to 0.6% with a negligible spatial drift. They demonstrated the operation of the […]
Metasurface opens world of polarization
Science Daily June 3, 2020 To achieve broad polarization manipulation, multiple birefringent materials need to be stacked one top of another making these devices bulky and inefficient. Researchers at Harvard University used topological optimization to design birefringent materials. They started with the functionality of the metasurface and allowed the algorithm to explore the huge parameter space to develop a pattern that can best deliver that function. The resulting metasurface was composed of nested half circles. The odd shapes have opened a whole new world of birefringence. They can achieve broad polarization manipulations; polarization can be tuned by changing the angle […]
Three research groups, two kinds of electronic properties, one material
Science Daily June 10, 2020 An international team of researchers (Israel, Germany) has shown that Bi2TeI (bismuth, tellurium and iodine ) is a dual topological insulator. It exhibits band inversions at two-time reversal symmetry points of the bulk band, which classify it as a weak topological insulator with metallic states on its ‘side’ surfaces. The mirror symmetry of the crystal structure concurrently classifies it as a topological crystalline insulator. They show the existence of both two-dimensional Dirac surface states, which are susceptible to mirror symmetry breaking, and one-dimensional channels that reside along the step edges. Their mutual coexistence on the […]
Observation of intervalley transitions can boost valleytronic science and technology
Science Daily May 15, 2020 When monolayer WSe2 absorbs a photon, a bound electron can be freed in a valley, leaving behind a hole resulting in an exiton. This is called an intravalley exciton which can emit light. The law of momentum conservation, however, forbids an electron and a hole in opposite valleys from recombining directly to emit light. As a result, intervalley excitons are “dark” and hidden in the optical spectrum. An international team of researchers (USA – UC Riverside, Taiwan, Japan) found that although the intervalley excitons are intrinsically dark, they can emit circularly polarized light. The optically […]