Everyone prefers to avoid the frustration of failing to achieve a desired outcome. Now it seems this even applies to materials and the arrangement of their atomic magnets, referred to as spins.
Researchers from RIKEN’s Nishina Center for Accelerator-Based Science in Wako, in collaboration with researchers from the University of Hyogo and Kyoto University, have uncovered an intriguing interplay between the arrangement of atomic spins and atomic interactions in the metallic compound Mo3Sb7.
The molybdenum (Mo) atoms in Mo3Sb7 crystals are arranged in octahedra. Unusually, the atomic bonds between the Mo atoms at the tips of the octahedra are stronger than between the Mo atoms in the plane. This leads to the formation of ‘dumbbells’ of Mo pairs along the three main crystal directions (Fig. 1). “The unusual arrangement between the dumbbells and the other Mo atoms makes this material unique and interesting to study,” comments Isao Watanabe from the research team.
Of particular interest is a sudden structural change that occurs at temperatures below 50 K (-223.15 °C). The origin of this phase transition has now been unveiled by a number of experiments that probe the magnetic and electric properties of the Mo atoms (1). These measurements present clear evidence that the phase transition is accompanied by symmetry changes in the crystal.
The symmetry changes are triggered by the spins associated with Mo atoms. The researchers found that an unusual competition in interaction between the Mo atoms takes place. At the phase transition, the strength of the interaction between the Mo atoms in the octahedra becomes comparable to the bond between the Mo atoms in the dumbbells. Consequently, the Mo atomic spins then begin to arrange in an up-and-down fashion along the entire crystal rather than within the dumbbells. However, owing to the particularities of the three-dimensional crystal structure, a periodic up-and-down arrangement, which is homogeneous across the entire crystal, is impossible. Frustration is the result.
To break this frustration the Mo octahedra elongate in one direction, breaking the crystal symmetry. This in turn finally allows the Mo dumbbells to order themselves periodically throughout the crystal in an arrangement termed a ‘valence bond crystal’.
The unusual competition of the atomic bonds between the Mo atoms in Mo3Sb7 has led to dramatic consequences involving crystallographic, electronic and magnetic properties. “This is the first example of its kind and we expect that this opens a new field to study similarly complex systems,” say Watanabe and his colleagues.
1. Koyama, T., Yamashita, H., Takahashi, Y, Kohara, T., Watanabe, I., Tabata, Y. & Nakamura, H. Frustration-induced valence bond crystal and its melting in Mo3Sb7. Physical Review Letters 101, 126404 (2008).
Organic light-emitting diodes become brighter and more durable
28.05.2018 | Technische Universität Dresden
APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
28.05.2018 | Event News
25.05.2018 | Event News
02.05.2018 | Event News
28.05.2018 | Trade Fair News
28.05.2018 | Physics and Astronomy
28.05.2018 | Event News