How can you speed up the time it takes to magnetize a ferromagnetic material using the Earth as the magnet?
origin is right. Heat and then slow cooling is the way to go. You have to make sure that there are no stray sources of magnetic fields around, too, because the Earth's field is weak. Why not use a stronger magnet to magnetise the material?
While working on the margins of the controlled fusion problem, I had a very low inductance 20KV condenser bank. I forget the capacitance, but it would have half cycle of only slightly more than a millisecond and peak current of several hundred thousand amps. We could dump the second half cycle not into our single turn Conical Plasma Gun via ignotrons shorting out the Gun's feed current path. I don't now remember why** but I wanted to magnetize a high hysterias loop rod perpendicular to its length. I made a "Hair-pin" loop conductor slightly longer than the rod with rod inside the hair pin (and thin mylar sheets on each side of it for insulation) and dumped the first half cycle thru that shorting hair pin - less inductance than the conical gun so took less time - perhaps 2/3 of millisecond? The "hair-pin was made by milling a slot in metal (Copper? - I forget) bar about 4 inches wide and one inch thick as ~500,000 amps or so flowing parallel but in opposite directions makes a huge peak force, trying to bend or split the more than 1 square inch cross sections of the hair pin sides. My transversely magnetized rod was a very strong. magnet - Every atom of the material must have been aligned the same way magnetically during that less than 1ms huge current pulse.* The splitting hair-pin impulse force on the ~ 1 by 2 inch square sides of the hair-pin may not have been able to explode it but just to be sure, there were several layers of glass fiber tape wound around the hair pin. * It was probably much more magnetizing force than needed, but I already had all but the hair-pin current loop. ** Needed very small diameter electric generator (or motor). The spinning rod and long narrow side coils was it. As I recall the unit's cross section was less than 16mm^2 (<4mm edges)
An iron magnet is due to some of the outer electrons of the iron atoms, all having the same spin. Below this is shown by the three single up arrows, in their own separated orbitals. This is at a slightly higher energy level, than if these same outer electrons paired via opposite spin, into fewer orbitals. Nonmagnetic iron has these same electrons into fewer orbitals than magnetic iron.The trick is to create a state of iron where the slightly higher magnetic configuration of the electrons, is the lowest possible energy state, so the magnetic is always on. This can be done with pressure like the earth does. Picture if the pressure, from nuke power, pushed on the magnetic iron, to maintain the magnetic state. Please Register or Log in to view the hidden image!
The picture was apparently stolen from: http://alchemy.cchem.berkeley.edu/jeff/JoeNaturechem.pdf. The explanation is incorrect. The reason that iron can be magnatized is due to an excess of unpaired electrons.
I find good diagrams, that express my visualization, with a simple google image search. These images are on the net to be shared. I share all the time, so I borrow when I need to. The number of electrons, in both nonmagnetic iron and magnetic iron are exactly the same. The difference has to do with how these electrons are stacked in orbitals. Magnetic iron has more unpaired electrons, and thereby uses more orbitals, whereas nonmagnetic iron will use fewer orbitals, pairing electrons to cancel out spin. The three same spin electrons within magnetic iron, implies magnetic iron is at higher potential, compared to the paired electrons of nonmagnetic iron; opposite spin will cancel. To maintain magnetic iron, we need to make the ground state of iron, become defined at the higher potential, so electrons can't fall down to the lower energy nonmagnetic state. The earth does this with pressure causing the electrons to stay excited; ground state is the magnetic state. Fusion power can be used to apply pressure to magnetics, so they stay always on and can't lose power. The analogy is winding a clock's spring. There are two states; wound and unwound, with unwind the lowest energy state. The unwound does not allow motion, and is the direction the spring will try to go. The trick is we need to keep the spring in the wound state, by turning the key constantly. There is a force being applied. This is not perpetual motion. We need to recycle some of the fusion energy output, to constantly wind the magnetic spring. We loose a little energy but the system is more stable and reliable.
It seems most of your post is hand waving. The issue is that you are implying that magnetizing iron will change the spin of the electron so they are all the same. That is not what happens. The electrons will not change spin so they are all in the same direction, the inherent spin of the electrons will align from the magnetic field and if the material is heated, for example, the atoms and magnetic domains can move and change orientaion so they are aligned, resulting in a permenant magnet.
You could accomplish a substantial reduction in the time required to produce such magnets by "pinching" the magnetic flux of external fields like that of the Earth from a larger to a smaller area with appropriately shaped and oriented ferromagnetic pole pieces. It might also help to raise the temperature of the soft iron to just below the Debye temperature of the magnet to increase the mobility of the atomic dipoles. The only other suggestion I can think of is to make thinner magnets rather than thicker ones. This works because aligning a large 3D volume of magnets in the same direction will in general require a stronger magnetic field than in 2D. The magnets will flip themselves to keep themselves magnetically unaligned in thicker volumes.
To answer the practical aspects of the OP, some heat applied to the iron rod is not a bad thing. Iron loses its magnetism at (I'm just stabbing at the figure, sorry) about 1200F. Forge workers who can't tell the exact color use the magnet method to know when the metal is ready to hammer. To magnetize the thing, align it with magnetic north when its about 400F and keep it steady while you strike one end sharply several times. Keep it aligned, let it cool, and you'll have a magnet. Not like stripping down old hard disks, but a magnet all the same. Please Register or Log in to view the hidden image!
Dr_Toad, that is awesome! I had no idea blacksmiths could produce weak magnets this way, but it makes perfect sense. I also strip down old hard disks for the magnets (and also to remove the media so that it will never be read again). I have a few from an old PDP-11 10 megabyte HD. They are very big, heavy and strong.
Anyone ever notice that when knives, forks, etc. come out of a hot dishwasher, they are often magnetized? Heating the metal allows for nearby magnetic fields (earth's, motors, etc.) to re-align the random magnetic fields, that all cancel to neutral field initially, to align with a magnetic field and make the knife, fork, etc. into a magnet when it emerges and cools. Yes, heat the metal, and have a nearby magnetic field, then cool to lock.
