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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Old Harry Scratches His Head Over Elementary Magnetics...
I've been puzzling over the nature of the magnetic domains, and wondered if folks might be able to help me out with some answers put in simple terms, to what I suspect are very simple questions to the woman or man who knows their magnetics.
1. Is there a sense in which a domain could be said to be located in a definite time and space as a singularity, or can a domain exist only in the context of other domains?
2. Imagining ourselves the femti-technologists of the future, if we started cutting a magnet up into ever smaller pices, would we ever arrive at a time when our femti-filings ( ) were the size of a single domain? What would that size be, and what would be the content of the space it occupied (if any)
3. If were to take an 'ideal' bar magnet, and cut it in two, would the sum of the domains in two cut halves be equal to the number of domains in the original uncut bar.
4. Does a magnetic field exist in the absence of an attractor, and if it does, how can we know?
5. Is a magnetic field a special case of the deformation of space-time?
6. If we to were to take a magnet formed from a metal wholly digestiblle in (for example only) aqua regia and place it at the heart of a sensing solenoid, would an EMF be induced in the inductance proportional to the rate at which the magnet was being dissolved?
7. I have read of, but not tried, a simple experiment in which a field coil is used to slowly reverse the field of a bar magnet. I understand that a sense coil, with an amplified output, will detect a series of clicks as the domains are reversed. With a more sophisticated set-up, what information would be contained in the amplitude, duration, and shape factor of the clicks?
8. In the experiment in 7. above, and with an array of suitable transducers arranged around the bar, would it be possible (in theory) to locate the origin of the click-pulse to a definite place within the bar?
9. In the first formation of an ideal permanent magnet within a magnetic field, and assuming a field rising from zero, would the formation of the first domains be ordered in some way, or probablistic?
Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
Hi Harry, Have a look at these sites for info on domains.
Overview:
Mathematical treatment:
In an oversimplified nutshell: domain size is related to the strength of spin coupling between the atoms of a ferromagnetic crystal and the size of the crystals. The atoms of the crystals are tightly coupled and hence form a domain while across crystalline boundaries/defect boundaries, domain walls tend to form as a result of the weaker spin coupling across defect boundaries....
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On the nature of the magnetic domains
) were the size of a single domain? What would that size be, and what would be the content of the space it occupied (if any)
