On Fri, 25 Nov 2005, Nick Reiter wrote: > Is anyone aware of a source of white noise in > electronic circuits that is related to either magnetic > domain or electron spin polarization? (Or > de-polarization?)
Barkhausen noise. Caused by the walls of magnetic domains suddenly becoming un-pinned and jumping to new shapes. It also appears on a transformer secondary when you apply slowly-varying DC to the primary. Also, some of the early radio detectors (from the pre-tube era) were based on this, where a motorized loop of thin iron wire was passed between pole pieces and the RF influenced the hiss and made a sort of pulsewidth modulated audio. It was also claimed to be a source of FE by these guys years ago: http://amasci.com/freenrg/bark.html http://jlnlabs.imars.com/spgen/barkhausen.htm Here's another which, if real, must be from Barkhausen effect: http://my.voyager.net/~jrrandall/CookCoil.htm > I've been playing with non- or > micro-inductive coils made from ferromagnetic > materials (nickel wire mainly) and I've found a neat > effect that manifests as a burst of strong hissy white > noise "whooshing" when a large magnet is moved by hand > toward the coil. Try using pieces of steel shim foil, or of transformer lamination. The noise seems to depend on how many pieces you stack up (with thin sheets giving fewer but louder clicks.) I've heard that metglas gives weird results but haven't tried it. And years ago there was a company selling single-domain iron fibers which would give huge pulses when the field hit a certain threshold and caused the entire fiber to switch. > Still, I've been thinking along the lines of spin-spin > communication, If a domain wall is getting stressed by a rising field and is about to flip, perhaps non-magnetic signals can determine when the click happens. If so, then Barkhausen radio detectors might also pick up non-EM signals. (((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))) William J. Beaty SCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775 unusual phenomena, tesla coils, weird sci
