Permanent Magnet: ON/OFF Mechanism...

[gyulasun]

This kind of change in magnets properties by a pulsed DC current can be current induced switching between opposite static magnetic spin directions,and happens through temporary DC current induced precession.You have a square wave DC pulses at frequency around 180 kHz.

Esa

Hi Esa,

You mention the 180kHz frequency. I would like to know why just around this frequency value happens something with permanent magnets?  Isn't there a even higher and better frequency like that because I can imagine any change in spin direction or similar effects in the magnets by exciting them in the higher GHz range? The 180kHz is way too low subharmonic in my mind.
Could you refer to some papers on the effects of the 180kHz frequency or similar frequencies on permanent magnets?
Or any other interesting info with respect to this?

Of course other people's opinion are also welcome.

Thanks
Gyula

[Esa Maunu]

I think that we should use relative weak Fe magnets in this experiment.The resonance frequency for the pulsed DC current depends of energy differencies on magnetic materials quantum level.
Here is two papers about this kind of systems,

About magnetic multilayers and coherent spin wave radiation creation,when DC current is directed perpendicular through magnetic multilayers.

http://arxiv.org/PS_cache/cond-mat/pdf/0012/0012337.pdf

In this paper is analyzed,how microwave radiation at Ghz level affects to Fe magnets magnetic properties.

http://www.weizmann.ac.il/home/fnsup/pdfs/Europhys.Lett.71,pp.110-116(2005).pdf

Esa

[valveman]

For those who want a square wave gnerator, a simple 555 timer circuit will do the trick.  If you want a kit that will work, you can order a complete frequency generator kit or simple 555 timer squarewave generator kit at:

www.qkits.com

Frankly, I think this squarewave magnet thing is BS but that's just my opinion.  If it worked then we would have seen others already replicating the results.

Valveman

[jake]

I think this squarewave magnet thing is BS but that's just my opinion.

Tell us how you really feel valveman!!!

Jake

[penguin hood]

On the first post that initiated the current topic, one specification to replicate the magnet ON/OFF phenomenon is:

Then connect these wires to a simple square wave generator circuit, capable of going up to 250khz.

Field dimishes on both poles. Square waves is AC with no DC offset. (A sine wave doesn?t do anything). The square wave needs to have a sharp leading edge.

One square wave of  frequency equal to Fo, is one sine wave of frequency Fo (called the Fundamental component) plus many lowest amplitude sine waves at multiple of Fo frequencies (called the Harmonic components).
For example, the following animation is one square wave synthesized by the sum of one fundamental sine wave plus 24 harmonic sine waves:

http://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Synthesis_square.gif/350px-Synthesis_square.gif

For one square wave with fastest rising and falling edges (shortest rise and fall time) but same amplitude and frequency parameters, the harmonic components will have highest amplitude and more harmonic components of highest frequencies is required while the fundamental remains unchanged.

From previous analysis:   
If to use a square waweform is too important then his rise time is important.
If there are a phenomenon, as some kind of resonance at Fo frequency, then a pure sine wave should produce the same effect than either one square wave of same Fo frequency, or than one square wave of lowest frequency such that Fo is multiple. (square wave of frecuency equal to Fo/N wherein N is a natural number).

I want say that if the phenomenon is produced by resonance at a highest frequency that 180 KHz (N x 180 KHz) and the square wave has low rise time then not effect because the harmonic component of frequency N x 180 KHz that excites the resonance is too weak or does not exist. Also this explains why a 180 KHz sine waveform doesn?t do anything and why the square wave needs to have a sharp leading edge.

In fact a known resonance phenomenon in ferromagnetic materials that serves as technique to probe the magnetic moment occurs at UHF frequencies:
http://en.wikipedia.org/wiki/Ferromagnetic_resonance