when working in high frequency magnetic field, It is well know that there are strong eddy current in the domain wall. according to the LLG equation, the moment in the domain will also rotate. I have read one paper written by Kittel, which say that the electrons responsilbe for the current and the moment are different part. so it seems that there should be circle current around the H field when the changing H field affect the single domain. But on the other hand, the moment will also make a process rotation, the B field nearby will also change, which will also lead to the circle current.
secondly, in addition to the heat loss from eddy current, the dampling of the LLG equation will result in the heat loss, which is related to the dampling factor.
so who can give the details on the three losses in the single domain?
Dear Zhimin,
The eddy currents only exist if you have free electric charge. This is the physical basic condition and also an external oscillating electromagnetic field to create the eddies. If you have a magnetic domain this only tell you that you have an oscillating magnetization following the field and producing you a superparamagnetic hysteresis loop which has no a magnetic heat source at all. Thus LLG damping factor is not enough to produce a current without able free charge which must be very small due to Faraday's small magnetic flux.
Hi, Prof. Baldomir, Thanks for your answer. So do you think the first eddy term from free changes could be only related to the conductivity not to rotation permeability? on the other hands, there is complex rotation permeability deduced from the LLG equation. do you think the magnetic loss could be determined from the imaginary permeability?
Dear Zhimin,
The eddy currents are only produced by the free electric charge under a variable magnetic field (Faraday's law). And my previous answer was given for a single domain (superparamagnetism), i.e. when the hysteresis losses were zero. Your question now is more general, and the complex permeability will give you losses as you said. But the application of LLG equations is quite subtle to tell you in general what are the losses without knowning the magnetic structure of the material.
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