Exchange coupling constant in micromagnetic simulation

In summary, the conversation was about finding the value of exchange constant for a material in the LLG equation. The unit for exchange constant is "J/m" and the typical value is 10^-11 J/m for some magnetic metals. However, it is difficult to derive this value based on the material's structure and the speaker was looking for a reliable source. One suggestion was to check the Nmag manual for generic values and another was to look up A = Exchange-stiffness constant on Wikipedia for a table of exchange constants for different materials.
  • #1
rocdawn
1
0
Hi, all.

I'm wondering if anyone's done some simulation of magnetic material with LLG equation. The question is where can I find the value of exchange constant for a material.

In LLG equation, the exchange constant is in the unit of "J/m", and the typical value is 10^-11 J/m, for some magnetic metal as far as I know. But I can't find a handbook or any online material summarizing this parameter for different materials. It seems complicated to derive based on the structure. Does anyone know where to look for such values?

Thanks in advance.
 
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  • #2
Hi,
Not sure if you still require this information but I am doing some similar work, using Nmag. http://nmag.soton.ac.uk/nmag/current/manual/manual.pdf contains some generic value's mostly for Permalloy (Nickel-Iron) which should be about 13e-12 J/m .

If you do find a better source please let me know as I am looking for something more concrete.

All the best
 
  • #3
I was confronted with the same problem, but the answer was in wikipedia: en.wikipedia.org/wiki/Exchange_interaction
Look up A = Exchange-stiffness constant
 

Related to Exchange coupling constant in micromagnetic simulation

1. What is the exchange coupling constant in micromagnetic simulation?

The exchange coupling constant is a material parameter that represents the strength of the exchange interaction between neighboring magnetic moments in a micromagnetic simulation. It determines the energy cost of aligning neighboring spins in the same direction, and is essential for describing the stability and dynamics of magnetic systems.

2. How is the exchange coupling constant calculated in micromagnetic simulation?

The exchange coupling constant can be calculated from the material properties of the system, such as the atomic spin density and lattice constant, using theoretical models or experimental measurements. It can also be directly fitted to experimental data or obtained from first-principles calculations.

3. What are the units of the exchange coupling constant in micromagnetic simulation?

The exchange coupling constant is typically expressed in energy units, such as joules per meter squared (J/m^2) or electron volts (eV), depending on the system and simulation method used. It can also be converted to dimensionless units by dividing by the magnetization saturation of the material.

4. How does the exchange coupling constant affect the behavior of a magnetic system in micromagnetic simulation?

The exchange coupling constant plays a crucial role in determining the stability, domain structure, and switching dynamics of a magnetic system in micromagnetic simulation. It affects the strength of magnetic interactions, the formation of magnetic domains, and the energy barrier for switching between magnetic states.

5. Can the exchange coupling constant be varied in micromagnetic simulation?

Yes, the exchange coupling constant can be varied by changing the material properties or by introducing external stimuli, such as magnetic fields or temperature. It can also be used as a tuning parameter to study the effects of varying the exchange interaction on the behavior of a magnetic system in micromagnetic simulation.

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