Repolarizing ceramic magnets.

[Hero999]

I've quickly read the Wikipedia article on neo magnets and the only difference seems to be the actual manufacturing of the metal blocks before they're magnetised. Both traditional ferrite and neo magnets are magnetised in exactly the same way, heat is applied along with a magnetic field. Neo magnets can also be made of polymer composites which can be moulded like any plastic. I doubt they are magnetised before being moulded and the polymer wouldn't stand up to much heating so I'd assume that they're just magnetised by brute force.

I don't see why you shouldn't be able to repolarise neo magnets but you'd need a huge amount of energy to do it.

 

[unclejed613]

one thing i did glean from the information i looked up was that there are two types of ferrite "hard" and "soft" ferrites, and this has nothing to do with material hardness. it's the magnetic properties.

Soft ferrites

Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. They have a low coercivity and are called soft ferrites. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies (SMPS).

The most common soft ferrites are manganese-zinc (MnZn, with the formula MnaZn(1-a)Fe2O4) and nickel-zinc (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz. MnZn have in comparison higher permeability and saturation induction.
 

Hard ferrites

In contrast, permanent ferrite magnets are made of hard ferrites, which have a high coercivity and high remanence after magnetization. These are composed of iron and barium or strontium oxides. In a magnetically saturated state they conduct magnetic flux well and have a high magnetic permeability. This enables these so-called ceramic magnets to store stronger magnetic fields than iron itself. They are cheap, and are widely used in household products such as refrigerator magnets. The maximum magnetic field B is about 0.35 tesla and the magnetic field strength H is about 30 to 160 kiloampere turns per meter (400 to 2000 oersteds).

a thought... i once built a screwdriver magnetizer with a bank of electrolytic capacitors a coil of about 20 turns of 12ga copper wire, and a large relay. i would charge the caps up to 50V or so, and then use the relay to dump their charge through the coil. with a screwdriver blade inside the coil, it would magnetize the screwdriver enough to to pick up quite a few screws. 3 treatments would make the screwdriver difficult to use, because it would attach itself to metal near the screw befor you could get it seated into a screw. magnetizing the small screwdriver bits for an electric screwdriver was interesting. the device liked to shoot the screwdriver bits across the room. i tend to think your magnetizer doesn't need to be on long enough to heat up at all, but a quick spike might do the job. and the trick is getting enough ampere-turns, not just the amount of current used 4 turns of wire carrying 75 amps creates the same field strength as one turn of wire carrying 300 amps.

 

[Sceadwian]

Shut up Hero, I think you're giving tcmtech ideas! Considering such high power usage in the magnetic domain will carry much like an AM signal if it has any low frequency components, I want times and possible frequency listings of anything tcmtech decides to try to build over peaks of a few hundred watts =)