MEMM

[PaulLowrance]

The following was just added to http://peswiki.com/index.php/Directory:MEMM

Note, there would be no applied field to the above images. There are several factors that determine domain size. First is temperature. Second is magnetic strength from ferromagnetic atom to ferromagnetic atom. Third factor that affects domain size with no applied field is grain or crystal size. The grain walls make it more difficult for the domains to extend beyond. So basically it's a battle between temperature & crystal size versus magnetic strength. An increase in temperature makes the domains smaller. An increase in ferromagnetic affective density increases domain size. Decrease in crystal size can decrease the domain size.

Image A is one domain. In order to achieve this for an appreciable amount of material, say 1 cubic inch, you have to lower the temperature to near absolute zero. In such a case the magnetic moments would all flip in alignment because there would no longer be the vibrating atoms to prevent such an alignment.

Now consider magnetic material in Image D. We have small domains at no applied field. If we then apply a saturating field we end up with one large domain (Image A). Image D has high potential energy. Image A has zero potential energy. Therefore, that energy must go somewhere. When the electrons flip they give off radiation. There are techniques to lessen the magnetic materials ability to absorb the radiation.

In a nutshell, there is more potential energy in Image D than Image C. It requires energy to make Image C go to Image D.

Lets say we saturate magnetic material. Now our material is one large domain, Image A. So you might ask how does the magnetic material get back to Image D. When we remove our applied magnetic field it is the ambient temperature (vibrating atoms) that knocks / forces the magnetic moments to reverse. Note that this requires energy because the magnetic moment is in alignment with the net magnetic field. So it is ambient temperature that forces the magnetic moments (intrinsic electron spins) to unaligned. If it were not for ambient temperature then it would require energy from our coil to cause the magnetic moments to become unaligned. That is the reason magnetic materials near absolute zero have square loop hysteresis, high coercivity.

What is happening when the material changes from Image D to Image A when we apply a saturating field is the magnetic moments are snapping in alignment, thus giving off energy. This heats up the magnetic material as it absorbs the radiation. When the applied field is removed the vibrating atoms knock the magnetic moments out of alignment, which slows down the atoms as it requires energy. This cools down the magnetic material. Although, what if we robbed the magnetic material of its radiation. This means the material would not heat up, but it would cool down, meaning we gain energy. This gain energy is in the form of electricity.

As previously described, the amount of radiation in some materials is in the megawatts for one cubic inch of material with a 100 KHz signal that changes the net internal field up to 1 T. In the section below titled, "Relevant Post" we see an example of amorphous and nanocrystalline material, Finemet, that possess 15 mega joules of energy exchages per second, 15 megawatts. Such material requires but a fraction of a watt to generate such a net internal field within the core. This fraction of a watt is a catalyst for 15 megawatts!

[MeggerMan]

Hi Paul,
Thanks for all the additional information.
I will digest this over the next few days.

Did you have any joy with getting samples for the Metglas C cores?
I have emailed them again requesting samples and filled in the form on their website so hopefully they will respond this time.
In the meantime I will build the pulse circuit with some minor updates to use better components.


Regards

Rob

[PaulLowrance]

Hi kingrs,

No, I haven't received metglas core yet. :-(

Is there any chance you could get the exact same parts that Naudin used?  If not then perhaps there are higher performance parts. Perhaps a MOSFET with higher breakdown voltage and faster switching speed. Although if the exact same parts are not used then that further changes the capacitance, etc. of the circuit.

I hope you get the "smoking gun" before me. Are you a perfectionist like myself? I'm still messing with the testing process of various types of cores.  A company sent me an interesting core that has a Curie Temperature of 43 C, permeability of 5500 and saturation of 1900 G.  It was ordered for its extremely low Curie temperature.  According to my MCE theory the magnetic moment boding strength is one of the major factors that determines domain size. So far this material is giving a lot of trouble. The temperatures can swing huge amounts one moment, but then hardly any the next. It might be for the reason that this core is very small and is actually touching the rod that goes down the center of the core. I use a thick aluminum rod as a single turn to decrease wire heat.

Regards,
Paul Lowrance

[PaulLowrance]

Hi mramos,

Naudin uses the BUZ11 MOSFET ->

Features:
Nanosecond switching speed
30A, 50V
rds = 0.04 ohms
High input impedance
Input capacitance is 1500 pF typical
Output capacitance is 750 pF typical

www.ortodoxism.ro/datasheets/fairchild/BUZ11.pdf

Looks nice. Fast switching speed, but somewhat low breakdown voltage.

I see digikey sells them for $0.84 in quantity of one:

http://www.digikey.com
just search for BUZ11

Paul Lowrance

[PaulLowrance]

Hi mramos,

20 cents each? What a deal!  Do you have any specs on them?

Paul Lowrance