# OOMMF Utilities 1.0

Object Oriented Micromagnetic Framework (OOMMF) is free, portable, extensible public domain micromagnetic program and associated tools, which was developed at the National Institute of Standards and Technology (NIST). OOMMF is very powerful and useful tool which can be thinly configured for different micromagnetic studies, but at the same time, it has one drawback — the multiformat output. This situation arose from a huge history of the project and different problems that have appeared before it, but it required a global solution.

For this goal our group created an additional package to the Wolfram Mathematica framework which was called «oommfUtilities» and can get micromagnetic data from each OOMMF-snapshot (.ovf or .omf-files) and it does not matter what the format of this file was: text or binary. Also our package can read the tabular text data which is hold on in .odr-files.

oommfUtilities.zip

In this archive one can find the main package, documentation, several OOMMF-snapshots and example-file for fun. Enjoy!

If you have any questions or suggestions, write to me: [encode_email email=»» display=»»]

# The results of scientific workshop: Spin-polarized current and spin-transfer torque

According to the results of the scientific workshop I want to publish final presentation and put it to the free access, you can find it by the link: Download

# Bloch Point Structure in a Magnetic Nanosphere

Authors:

Publication:

Phys. Rev. B 85, 224401 (2012), 10.1103/PhysRevB.85.224401

8 pages, 7 figures

arXiv:

http://arxiv.org/abs/1112.2413

The micromagnetic singularity, the so–called Bloch point, can form a metastable state in the nanosphere. We classify possible types of Bloch points and derive analytically the shape of magnetization distribution inside diﬀerent Bloch point. We show that external gradient ﬁeld can stabilize the Bloch point: the shape of the Bloch point becomes radial–dependent one and compute the magnetization structure of the nanosphere, which is in a good agrement with performed spin–lattice simulations.

## Supplementary materials

Bloch point relaxation in a nanosphere

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 Sphere diamter $2R_\text{out} = 35a_0$ Exchange length $\ell=3.95a_0$ External magnetic field $\textbf H = 4\pi M_\text{sat} \textbf {R}/R_\text{out}$ Damping parameter $\eta = 0.5$ Time is measured in $\hbar/JS^2$

Here $a_0$ is lattice constant.

# Controlled vortex core switching in a magnetic nanodisk by a rotating field

Authors:

Volodymyr P. KravchukDenis D. Sheka, Yuri Gaididei, Franz G. Mertens

Publication:

J. Appl. Phys. 101, 043908 (2007), 10.1063/1.2770819

5 pages, 5 figures

arXiv:

http://arxiv.org/abs/0705.2046

The switching process of the vortex core in a Permalloy nanodisk affected by a rotating magnetic field is studied theoretically. A detailed description of magnetization dynamics is obtained by micromagnetic simulations

## Supplementary materials

The switching dymanics of permalloy disk was obtained using OOMMF numerical simulations.

Geometry parameters:

• shape — disk
• disk diameter — 132 nm
• disk thickness — 20 nm

Material parameters:

• material name — permalloy
• saturation magnetization — 8.6e5 A/m
• exchange constant — 1.3e-11 J/m
• damping constant — 0.006

### The dynamics of the perpendicular to the disk plane magnetization component.

The magnetic field orientation is denoted by the arrow. The parameters of applied mag. field are the following:

• amplitude — 0.02 T
• frequency — 10 GHz (orientation is oposite to the vortex core polarization)

### The dynamics of the in-plane magnetization component.

The out-of-plane magnetic field component is denoted by the levels of gray color. The parameters of applied mag. field are the following:

• amplitude — 0.07 T
• frequency — 10 GHz (orientation is oposite to the vortex core polarization)

The dashed blue and the solid yellow curves represent My=0 and Mx=0 isosurfaces, respectively; the black and the white curves correspond to Mz/MS = 0.75 and Mz/MS=-0.75 isosurfaces, respectively.

# Vortex polarity switching by a spin-polarized current

Authors:

Jean-Guy Caputo, Yuri Gaididei, Franz G. Mertens, Denis D. Sheka,

Publication:

Phys. Rev. Lett. 98, 056604 (2007), 10.1103/PhysRevLett.98.056604

4 pages, 3 figures

arXiv:

http://arxiv.org/abs/cond-mat/0607362

The spin-transfer effect is investigated for the vortex state of a magnetic nanodot. A spin current is shown to act similarly to an effective magnetic field perpendicular to the nanodot. Then a vortex with magnetization (polarity) parallel to the current polarization is energetically favorable. Following a simple energy analysis and using direct spin-lattice simulations, we predict the polarity switching of a vortex. For magnetic storage devices, an electric current is more effective to switch the polarity of a vortex in a nanodot than the magnetic field.

## Supplementary materials

Switching picture from numerical simulations on a square lattice with circular boundary.

 Disk diamter 200a Anisotropy coefficient 0.03 a Damping coefficient 0.01 Degree of spin polarization 0.25 Spin current -0.003