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DW propagation velocity

DW propagation velocity

(OP)
Hello
Where can one find domain wall propagation velocity for materials like soft/hard ferrites or electrical steel? Nothing fancy or nanoscale, only regular magnetic flux paths.
It must depend on grade and composition but it's strange that doesn't get specified. Or is there an other name to look for?
I've seen papers refering to values of 1000 m.s in some alloys. Thats gives an idea what to expect, but surely that will change for orders of magnitude from one to another.
Do you have pointer to figures, please?
Best

RE: DW propagation velocity

It is pretty fast. You might find some information about it in papers discussing Barkhausen signals.

RE: DW propagation velocity

It depends on the microstructure and applied fields. 1000m/s seems un-realistic, too fast. but I am not very sure if it can incur in some special alloys. i think the normal speed is at millmeter scale per second. Before Barkhausen jumps, DW movement shoud be pretty slow, even at Barkhausen period, it is unlikely jump to 1000 m /s, otherwise, we will not be able to mesure the steps (jumps) from the magnetization curve, since the measurement (signal pick up) takes time.

I have ever found that, for permenent magnets, VSM measurement gave a higher coercivity than SQUID. That was because VSM normally is set up to pick up data points faster than SQUID. That could also mean the measurment speed is faster than domain wall propagation or domain reversal process. so mm/s scale sounds more realistic to me.

RE: DW propagation velocity


Domain wall velocity as such is an un-important or a minor variable. Where wall motion can be identified in the devices you indicate, maximum velocities are on the order of 100 m/s at best. Other mechanisms quickly dominate the flux reveral process and are much faster.

RE: DW propagation velocity

MagBen, you seem to be implying the "coercivity" is exclusive to domain wall motion. Seems that the flux reversal process taken as a sample average is a bit more involved.

RE: DW propagation velocity

The manipulation of Hc seems to be more related to reversal. For permanent magnets, domain wall pinning mechanism for Hc seems to be more popular than nucleation and reversal. This a different topic, but may related to domain wall displacement.
I personally never measured speed of DW, but i did read some research papers saying it was a couple of mm/s. But i cannot say 100 m/s is impossible.

RE: DW propagation velocity

The 100 m/s is a typical maximum at which a domain wall can even be defined. In transformer steels, eddy currents reduce it considerably. Regardless, the velocity itself is not a useful characterization of the material.

RE: DW propagation velocity

(OP)
Thanks for pointing to Barkhausen effect, it yeld interesting reading. Seems like domain-wall velocity wasn't relevant. I lack a LOT of knowledge on magnetic and get things mixed up.
The question came from an attempt to understand why some poorly designed transformers with long cores show a voltage phase shift on secondary, seen when operated had higher frequency than designed for. An effect happening at about 20 to 100 m/s looked as a good candidate for that empiric and pagan interpretation censored

RE: DW propagation velocity



If you take a look at the equivalent circuit of a transformer (internet search is simple enough), the source of your phase shift will be come more evident.

For frequencies well above the thransormer design condiiton, you will also need to include the winding capacitances, etc.



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