Science topic

Micromagnetic Simulation - Science topic

Explore the latest questions and answers in Micromagnetic Simulation, and find Micromagnetic Simulation experts.
Questions related to Micromagnetic Simulation
  • asked a question related to Micromagnetic Simulation
Question
2 answers
In micromagnetic simulation based on FDTD, the simulation space needs to be discretized. I have a permalloy structure with dimensions 1000 nm x 100 nm x 30 nm. Permalloy magnetostatic exchange length ~5.69 nm. Is it valid to take a cell which is 30 nm along z?
I really appreciate any suggestions and explanations.
Regards,
Anirban
Relevant answer
Answer
In general, it is widely accepted that the discretization length (D) for a reliable
micromagnetic simulation should be in the range of a0 << D <lex, being a0 the crystalline unit cell parameter and lex the exchange length.
In principle, you are proposing a cell with a z length larger than lex, so you are losing information regarding any changes of the magnetization along the z axis.
However, I found that some researchers [1, 2] consider that a discretization length (D) slightly larger than lex (about 2 or 3*lex), can be used under certain circumstances. This would be valid as long as “D stays sufficiently small with respect to other characteristic length scales in the material as the thickness of a domain wall or a vortex size” [2].
For example, this could be the case when the simulation conditions are forcing the spins to stay inside in the x-y plane of the film due to a strong in-plane anisotropy, a very thin film (z<<< x, y) or a strong applied magnetic field being larger than the anisotropy field (Happl>>HK). Under these circumstances, you probably can take a longer discretization length along the z axis without losing valuable information.
In any case, you must verify the reliability of your results by checking the angle between adjacent spins, which always must be lower than PI/2. This is due to the mathematical formulation of the exchange energy in micromagnetics, as explained in [3]. Also, it is advisable to perform convergence test of your simulations with different cell sizes; this is done in order to assure that you are arriving to the same solution regardless of the cell size.
References
[1].- S.Wang, D. Wei and K. -Z. Gao, "Limits of Discretization in Computational Micromagnetics," in IEEE Transactions on Magnetics, vol. 47, no. 10, pp.
3813-3816, Oct. 2011, doi: 10.1109/TMAG.2011.2157474.
[2].- B. Van de Wiele, L. Dupré, F. Olyslager, "Influence of space discretization size in 3D micromagnetic modeling", Physica B: Condensed Matter, Volume 403, Issues 2–3, 2008, Pages 372-375, https://doi.org/10.1016/j.physb.2007.08.052.
  • asked a question related to Micromagnetic Simulation
Question
2 answers
In which OXs_Energy or Oxs_Evolver class, we can introduce spin hall effect and specify the spin hall angle in an OOMMF .mif file?
Relevant answer
Answer
hi,have you fixed this problem?
  • asked a question related to Micromagnetic Simulation
Question
4 answers
Hi All,
I am wondering how can I simulate antiferromagnetic skyrmion in either OOMMF or Mumax?
Do I have to simulate two separate layers?
Relevant answer
Answer
Micromagnetics is a continuum theory; you start from a discrete Heisenberg model and take the continuum limit of this. Antiferromagnetism inherently breaks the continuum assumption (i.e. that spins vary only slowly) and so micromagnetic simulations are not appropriate for this type of study.
In the past people have used OOMMF/MuMax to look at antiskyrmions, but it is ill-advised. While some energy terms in the Heisenberg Hamiltonian have the same mathematical form as the micromagnetic equivalent and can therefore be mapped to the discrete equivalent simply by multiplying by appropriate constants, this is not true in all cases.
There are a few publicly available tools that can do Heisenberg model simulations and they all have a somewhat different focus.
  • asked a question related to Micromagnetic Simulation
Question
2 answers
Hi, I'm doing a project by creating micromagnetic simulation for various materials using oommf. I need some more details regarding the simulation details and initialmag part of the probEd part in the framework? Thanks
Relevant answer
Answer
Siva Sankaran The application mmProbEd provides a user interface for creating and editing micromagnetic problem descriptions in the Micromagnetic Input Format (MIF 1.1). mmProbEd also acts as a server, supplying problem descriptions to running mmSolve2D micromagnetic solvers.
References:
  • asked a question related to Micromagnetic Simulation
Question
7 answers
Assume that multiple skyrmion lattice is formed by applying out-of-plane field to a ferromagnetic multi-domain state.
Relevant answer
Answer
Ok. Should it not be related to the reversal curve instead of first magnetization curve?
  • asked a question related to Micromagnetic Simulation
Question
5 answers
Dear all, Has anyone here used the OVITO (http://ovito.org/index.php) program or the Rasmol (http://www.openrasmol.org/) program ???
I want to generate the example image of the site simulations: 
However I'm not getting success ... I use windows, if someone can help me I'll be grateful.
Relevant answer
Answer
Hello,
I have used Ovito under Linux, with no problems. Not only for creating static images, also for animated movies.
Perhaps you could explain some more what are the problems you are having?
Regards,
  • asked a question related to Micromagnetic Simulation
Question
2 answers
I'm working with the Stoner-Wohlfarth model with 5 energy terms and I want my system to evolve into a larger system with more possibilities of interaction (dipole interaction) and with different anisotropies from different angles ... It is possible to make Stoner's model -Wohlfarth (coherent rotation of magnetization) in a micromagnetic model? Any possibility or solution to this case?
Relevant answer
Answer
Basically you can keep the microscopic dipoles aligned if you artificially increase exchange interaction. Exchange keeps neighbouring dipoles oriented in the same direction. But there will be always small deviation - because exchange is quadratic in small deviation and thus small deviations carries small to second power = very small energy contribution. In this sense you will never get "perfectly aligned" elementary moments in the micro-magnetic simulation.
  • asked a question related to Micromagnetic Simulation
Question
5 answers
I have a grid of 128x128x4, the amount of grains is limited by the grid number or can I vary the number of grains? How do I define 100 grains, for example, in a simulation of an FM/AFM bilayer with Exchange Bias?
Relevant answer
Answer
Thanks!
I will try to reproduce ... you said that you have to give the parameters for each region, but if I already define my 2 layers as region 0 and region 1, will not conflict with the regions defined for the beans? for example, 100 grains goes from 0-99, the regions of the layers will have to be 100 and 101?
  • asked a question related to Micromagnetic Simulation
Question
4 answers
I want to simulate a magnetic hysteresis cycle that has displacement in the field ... any suggestions?
Thanks a lot.
Oreci.
Relevant answer
Answer
It can be done using MuMax3 as is shown in the papers 'Modelling exchange bias with MuMax3' ( ) and Modelling compensated antiferromagnetic interfaces with MuMax3 ( )
  • asked a question related to Micromagnetic Simulation
Question
1 answer
material studio
Relevant answer
Answer
Hi
If you are simulation more than one chain (Say, 4 chains). You may want to create 4 xsd fies, and construct these 4 chains. Then, this error would not happen.
  • asked a question related to Micromagnetic Simulation
Question
4 answers
  1. Can applied field affect the DWs confiugration.?
  2. If it affects than what field should we applied so that we got this Phase diagram.
Relevant answer
Answer
Dear Sourabh Aneja,
1.) yes, certainly. If a field is large enough then the material will be magnetically saturated and domain walls thus are expelled. From this very qualitative statement alone it is clear that an applied field does have an influence.
2.) that is a difficult question to answer generally, since the effect of the field will depend on the materials parameters you enter to the simulation (in your case the parameters for permalloy). Note also that in general there may exist multiple metastable domain configurations for a given element.
I would therefore guess that several configurations were calculated (for each combination of width and thickness) and total energies compared to reach the phase diagram shown in the figure you appended. The "phase boundaries" then designate those parameters where the character of the lowest energy configuration changes. [Thats what I hope to be an educated guess concerning the figure]. It could even be that a number of alternative domain configurations were additionally tested. On the other hand I would also think that the basic configurations for permalloy should be pretty well established.
Probably the #1 reference for insight into magnetic domains is the book I linked below.
You may also want to look into the paper I additionally linked; you will see the domain configs these authors considered in what I think is a similar problem.
  • asked a question related to Micromagnetic Simulation
Question
5 answers
I am working on magnetism in nano dimensions and currently synthesized magnetic nano-structures using chemical methods but i don't have good magnetic characterization techniques. Please suggest some good and open source software so that I can simulate my material properties and then experimentally characterize my samples somewhere else?
Relevant answer
Answer
OOMMF is one of the most commonly used micro-magnetic simulations.... its free and can simulate 3D structures. Gives plenty of parameters including different types of energies.
You may also check one more software 'Magpar'