In the Physical Review Letters study, the researchers sought to understand how energy is sustained and spreads in magnetic materials—“magnetic fire.” Such knowledge is important in designing magnetic materials for energy storage applications. This is because magnetic fire can lead to a rapid and uncontrolled release of stored energy, producing significant energy loss in, for example, an electrical generator.
Research on bursts of energy within magnetic systems dates back two decades. But scientists haven’t been able to measure and understand what prompts this phenomenon, known as “magnetic deflagration.”
Part of this mystery lies in the nature of chemical reactions. In such reactions, which produce heat, the energy released is determined by the chemical constituents and cannot be easily varied. What is known as an “activation energy” is typically necessary to start a chemical reaction; energy is then released as the reaction proceeds. In other words, scientists have concluded that a spark is needed to begin this process—much the same way a forest fire begins with a single lit match.
But in magnetic materials the energies can be manipulated by magnetic fields and are therefore very easily varied in an experiment. Thus the activation energy and the energy released are controllable, enabling systematic studies of the physical mechanisms of energy flow.
To achieve this, the researchers surmised they could produce such a “spark” through a series of spins—the chemical equivalent of striking a match. In this case, they employed small single crystals of a molecular magnet— each magnetic molecule being just one billionth of a meter—that could be magnetized, much like the needle of a compass. The researchers provided a pulse of heat as the spark, causing molecular spins near the heaters to flip in a magnetic field, a process that released energy and transmitted it to nearby material.
“When the molecules’ spins are aligned opposite the applied field direction, they possess a high level of energy,” explained Andrew Kent, a professor in NYU’s Department of Physics and the study’s senior researcher. “And then when the spins ‘flip,’ energy is released and dispersed into surrounding magnetic material that can cause a runaway reaction.”
Moreover, the scientists were able to control the speed of this process by adjusting the make-up of the magnetic field in their experiments. Through this detailed examination, they could see under what conditions energy is released and how it propagates.
“These are exciting results and ones that have prompted us to further consider whether a spark is even necessary to start a magnetic fire,” added Kent. “We hope to observe and study situations in which the fire starts spontaneously, without a spark.”
The study was conducted at NYU by Pradeep Subedi and Saul Velez, both doctoral candidates, as well as Ferran Macia, a postdoctoral researcher, and included: Shiqi Li, a City College of New York (CCNY) doctoral candidate; Myriam Sarachik, a professor at CCNY; Javier Tejada, a professor at the University of Barcelona; Shreya Mukherjee, a University of Florida doctoral candidate; and George Christou, a professor at University of Florida.
The research was supported by a grant from the National Science Foundation’s Division of Materials Research (DMR-1006575, DMR-0451605) and Division of Chemistry (CHE-0910472).
James Devitt | EurekAlert!
Glass's off-kilter harmonies
18.01.2017 | University of Texas at Austin, Texas Advanced Computing Center
Explaining how 2-D materials break at the atomic level
18.01.2017 | Institute for Basic Science
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences