[nmag-users] Spin angle of multi-body system

[Alessandro Schaer]

Dear all,

I am simulating multi-body systems like the two cubes example of the documentation (http://nmag.soton.ac.uk/nmag/0.2/manual/html/example_two_materials/doc.html). I need the bodies to be made of different materials, thus I define the different magnetic materials Material1, Material2, and so on.

In order to verify the accuracy of my results I need to look at the maximum spin angle. By using the ncol tool to visualise the data stored as results I see that there is one vector of maximum spin angles for each material, namely the data maxangle_m_Material1, maxangle_m_Material2, ...

The problem I encountered is that only maxangle_m_Material1 contains some nonzero values. All other maxangle_m_MaterialN are empty (all values are exactly 0, not even 0.0000).

My question is whether this is normal, i.e. the maximum spin angle is computed and stored for the entire system and thus only one value is returned, or not.

If not, is there something "special" I need to consider when simulating such systems?

As a note, the simulation did not return any error message at all.

Thank you in advance. Regards,

Alessandro Schaer

[Fangohr H.]

Dear Alessandro,

On 5 May 2014, at 12:13, Alessandro Schaer <alessand...@gmail.com<mailto:alessand...@gmail.com>> wrote:

Dear all,

I am simulating multi-body systems like the two cubes example of the documentation (http://nmag.soton.ac.uk/nmag/0.2/manual/html/example_two_materials/doc.html). I need the bodies to be made of different materials, thus I define the different magnetic materials Material1, Material2, and so on.

In order to verify the accuracy of my results I need to look at the maximum spin angle. By using the ncol tool to visualise the data stored as results I see that there is one vector of maximum spin angles for each material, namely the data maxangle_m_Material1, maxangle_m_Material2, ...

The problem I encountered is that only maxangle_m_Material1 contains some nonzero values. All other maxangle_m_MaterialN are empty (all values are exactly 0, not even 0.0000).

My question is whether this is normal, i.e. the maximum spin angle is computed and stored for the entire system and thus only one value is returned, or not.
If not, is there something "special" I need to consider when simulating such systems?

I would think that the spin angle should be computed per region; that is certainly what the column headers seem to suggest. However, you may well have found a bug.

Other reasons why the spin angle is zero could be that you have exchange coupling but nothing that disturbs the magnetisation in a spatially non-uniform way (no demag?)

Finally, if may be worth noting that if you only save the relaxed states (such as in a hysteresis loop, say), the max_angle will only record the maximum angle of the relaxed configuration (i.e. what you can see via ncol does not reflect what maxangles may have occurred in the dynamics that have led to the recorded state).

I hope this is of some use.

If your data is still suspicious, you could circulate a complete test so that others can see in more detail what you have done, reproduce and comment.

Regards,

Hans