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Counterpart of the Darrieus-Landau instability at a magnetic deflagration front
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0003-3096-1972
Chalmers University of Technology.
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2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 93, no 13, 134418Article in journal (Refereed) Published
Abstract [en]

The magnetic instability at the front of the spin avalanche in a crystal of molecular magnets is considered. This phenomenon reveals similar features with the Darrieus-Landau instability, inherent to classical combustion flame fronts. The instability growth rate and the cutoff wavelength are investigated with respect to the strength of the external magnetic field, both analytically in the limit of an infinitely thin front and numerically for finite-width fronts. The presence of quantum tunneling resonances is shown to increase the growth rate significantly, which may lead to a possible transition from deflagration to detonation regimes. Different orientations of the crystal easy axis are shown to exhibit opposite stability properties. In addition, we suggest experimental conditions that could evidence the instability and its influence on the magnetic deflagration velocity.

Place, publisher, year, edition, pages
2016. Vol. 93, no 13, 134418
Keyword [en]
Molecular magnets, Flames, Mn-12-acetate, Stability, Fusion
National Category
Condensed Matter Physics
Research subject
URN: urn:nbn:se:umu:diva-119332DOI: 10.1103/PhysRevB.93.134418ISI: 000373974800005OAI: diva2:920088
Swedish Research Council
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2016-08-12Bibliographically approved
In thesis
1. Magnetic deflagration and detonation in crystals of nanomagnets
Open this publication in new window or tab >>Magnetic deflagration and detonation in crystals of nanomagnets
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis we cover the dynamics of the macro magnetic transformations (spin avalanches) in crystals of molecular nanomagnets, also known as magnetic deflagration and detonation.

Taking a single-molecule Hamiltonian, we calculate the dependence of Zeeman energy and the activation energy as a function of an external magnetic field at different angles relative to the easy axis of the crystal. Using quantum mechanical calculations, we show that the energy levels of the molecule exhibit complex behavior in presence of a transverse component of the magnetic field. For an arbitrarily aligned magnetic field, the energy levels do not arrange in a simple "double-well" manner. We extend existing theoretical models by generalizing the Zeeman energy for a wide range of magnetic fields and its different orientations.

We obtain a new type of front instability in magnetization-switching media. Due to the dipole-dipole interaction between the molecules magnetic instability results to the front banding and change in the front propagation velocity. The magnetic instability has a universal physical nature similar to the Darrieus-Landau instability. The instability growth rate and the cutoff length are calculated for the spin avalanches in the crystals of nanomagnets.

Finally, we investigate the internal structure of the magnetic detonation front. We calculate the continuous shock profile using the transport processes of the crystal such as thermal conduction and volume viscosity. Such an approach can be applied to any weak shock wave in solids. Zero volume viscosity leads to an isothermal jump, i.e., the temperature changes continuously while the pressure and the density experience discontinuity. The analysis has shown that the volume viscosity plays a major role in the formation of the detonation front.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 40 p.
Nanomagnets, magnetic deflagration, front instability, Zeeman energy, magnetic instability, magnetic detonation, weak detonation
National Category
Physical Sciences
Research subject
Physics Of Matter
urn:nbn:se:umu:diva-124445 (URN)978-91-7601-534-6 (ISBN)
Public defence
2016-09-05, MC413, MIT-huset, Umeå, 13:00 (English)
Available from: 2016-08-15 Created: 2016-08-11 Last updated: 2016-08-15Bibliographically approved

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Jukimenko, OlexyDion, Claude M.Bychkov, Vitaly
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