While that’s a very clever idea, I wonder if anyone has seen a device that is KNOWN to have that construction.
I ask because the alternating domains aren’t so much reacting to the dipole orientation in an unmagnetized ferromagnetic substrate as inducing an opposing ferromagnetic dipole.
I can see the suggested mechanism working, especially if the magnets weren’t very strong in the first place (e.g. flexible magnetic material) especially with the field lines oriented perpendicular to the surface of the “striped” sheet: when the sheet is alone, the lines of manetic force would go directly between the adjacent stripes wirh very little “side leakage” (field lobes) to induce a dipole in an unmagnetized ferromagnetic substrate, and the confounding effects of the random domain orientation in the unmagnetized bulk material would have reduce the effective field even more (one reason magnetic fields penetrate magnetic materials poorly) However, when applied to a matching striped dipole, the lines would flow almost as evenly to the “partner” sheet as to the adjacent stripe in the same sheet,a d since the partner dipole is premagnetized, rather han weakly indiuced, the attraction could be quite strong.
I seem to recall working through all this as an undergrad, doing Hallidane and Resnick. My question is – has anyone specifically seen this in action or done the math recently in a Physics problem set?
Also, has anyone done the math for other combinations? E.g. If we allow two opposing orientations in the three axes defined by the edges of the stripes, how much preference would a pattern of stripes show for its partner vs. a nonmatching pattern? Would this only work effectively with alternating stripes?
In re: office use
Stray fixed magnetic fields actually pose a negligible risk to data on magnetic media. Since I can’t find a link to one of these experiments, I urge you to NOT take my word for it. Go ahead and try to induce a data error in a floppy with a permanent magnet. Dust or grease is far more likely to cause errors
The real danger, if any, comes from rapidly changing, and especially alternating magnetic fields. e.g. Bulk demagnetizers create an alternating field NOT a strong fixed field; unshielded speakers or the degaussing coil on your monitor can do more damage withtheir rapidly changing flux than even a fairly strong slow field, like the ringer on an old style telephone.
The deliberate magnetization of recording uses a strong field to orient a sizeable (but still fairly small) minority of the domains. Almost any standard college text will list the theoretical magnetism of plain iron if the domains were 100% oriented; it’s stunningly beond anything we’ve achieved with any high-tech materials.
However data corruption tends to operate on the “give me an excuse” principle. Since the vast majority of domains in magnetic media are NOT aligned, rapidly changing fields can ‘jiggle’ susceptible domains, which may, int turn, affect nearby domains somewhat. The more dense the data in a recording, the fewer domains would suffice to flip a bit. Remember: 90%+ were never contributing anyway.
I would actually worry that such small scale striped field might be more effective at demagnetizing or scrambling magnetized media than the fixed fields it’s meant to replace. Neither would pose any real danger at a distance of several centimeters, but while a kitchen magnet will do little damage if you slide on the back of a floppy, the “striped kitchen magnet” might look like a rapidly alternating field.