Micromagnetics

By the Group of Lance De Long, UK Physics and Astronomy Dept.
The De Long Group is involved in running simulations using the OOMMF (Object Oriented MicroMagnetic Framework) software from NIST as well as other micromagnetic solvers. The OOMMF software imports a magnetic geometry with some initial configuration and then proceeds to calculate the evolution of the geometry as time (and/or field) evolves. The geometry is meshed and allows us to calculate the solution to differential equations by using the method of finite difference (OOMMF, MuMax) or finite element (Nmag). The evolution is calculated through two computational methods; time integration (i.e., Runge Kutta time integration) or energy minimization (specifically, conjugate gradient method/steepest decent). The solvers we use run on a single node and are capable of using all processors on a given node. The solvers are bottlenecked by the processor and are not memory intensive; therefore, most calculation is done on regular compute nodes, with jobs ranging from 1 hour to 3-4 days. The group also uses Python along with NumPy, SciPy, and matplotlib libraries; this is used for analyzing the datasets produced from the solvers. Specifically, we use Numpy for FFT of data and matplotlib for plotting. The Python scripts are mostly memory intensive and some require a FatNode to be able to load the datasets into memory.

Students

The graduate students working on this project are:
Barry Farmer
Vinayak Bhat

Ali Frotanpour

Amrit P Kaphle, Added 06/01/2021

Softwares

OOMMF
MuMax
Nmag
NIST
Python
NumPy
SciPy
matplotlib libraries

Publications

2016 - 2019

“Dynamic origin of segment magnetization reversal in thin-‎film Penrose tilings”, Federico Montoncello, Loris Giovannini, Barry Farmer and Lance E. De Long, J. Magn. Magn. Mats. 423, 158-163 (2017).
“Macrospin reversals and spin wave softening in isolated nodes of Kagome-like structures: statics and dynamics”, F. Montoncello, L. Giovannini, J. B. Ketterson, W. Bang, L. E. DeLong and B. Farmer. Proceedings of INTERMAG Europe 2017, Dublin, Ireland (EU), April 24-28, 2017; 2017 IEEE International Magnetics Conference (INTERMAG), pp. 1-1 (2017).
"Coupled macrospins: Mode dynamics in symmetric and asymmetric vertices", Wonbae Bang, Matthias B. Jungfleisch, Federico Montoncello, Barry W. Farmer, Pavel N. Lapa, Axel Hoffmann, Loris Giovannini, Lance E. De Long and John B. Ketterson, AIP Advances 8, 056020 (2018); doi: 10.1063/1.5007281
“Mutual influence between macrospin reversal order and spin-wave dynamics in isolated artificial spin-ice vertices”, F. Montoncello, L. Giovannini, W. Bang, J. B. Ketterson, M. B. Jungfleish, A. Hoffmann, B. W. Farmer and L. E. De Long, Phys. Rev. B 97, 014421 (2018).

We have recently published an important paper in Physical Review Letters:

(Bhat et al. Phys. Rev. Lett. 111, 077201 (2013) that acknowledges UK CCS support.
V. Bhat et al., IEEE Transactions on Magnetics—Conferences, 49(7), 3101-3104 (2013).

Collaborators

We have an ongoing collaboration with Prof. John B. Ketterson of Northwestern U. Dept. Physics and Astronomy, which relies upon the output of our UK simulations.

Grants

Delong, Lance NO ID SEMPA Study of the Nucleation, Stability and Dynamics of Ferromagnetic Vortices....." Oak Ridge Associated Universities 4/9/2012 - 2/28/2014 $800
Delong, Lance DE-FG02-97ER45653 Disorder and Topological Defects in Magnetically Frustrated Single Crystals and Thin-Film Metamaterials Department of Energy 9/1/1997 - 5/14/2015 $510,530
Delong, Lance DE-FG02-97ER45653 Competing Interactions in Complex Transitions in Complex Transition Metal Oxides $385,000 Department of Energy 9/1/1997 5/14/2014

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