Are there any materials that magnets can stick to, but the material itself cannot be made magnetic?
A magnet will stick to a piece of ordinary steel even though the steel itself is not magnetic. However, you could treat that piece of steel and turn it into a magnet. Is that true for all materials?
Depends on the retentivity characteristic of the material. Retentivity is the ability to hold a magnetic “charge”, or to stay magnetized after the applied external field has been removed. The materials used in transformer cores, for example, are designed to have low retentivity, since it would be a major drawback if the core remained magnetized after the first time power was applied. Magnetic materials are broadly classified as magnetically “hard” or “soft”. Magnetically soft materials have low retentivity while hard materials have high retentivity. The latter make excellent permanent magnets, while the former do not. However, magnets will stick to both kinds of materials regardless of retentivity. And of course there are steels, like austentitic stainless steels which are nomagnetic.
Most of the materials to which a magnet will stick strongly enough to notice are what are called ferromagnetic materials. Iron and nickel, and most alloys made from them, are in this category. All ferromagnetic materials can be magnetized. However, there are also some materials which are called paramagnetic: These materials will be attracted to a magnet (though usually not as strong as a ferromagnetic material), but when you take the magnet away, the magnetization of the material goes away completely. I believe liquid oxygen is in this category (if you pour a stream of liquid oxygen near a strong magnet, the stream will be deflected towards the magnet). And there are even some substances, called diamagnetic, which are actually weakly repelled by a magnet. Everything which isn’t ferromagnetic or paramagnetic is diamagnetic to some degree; the simplest example is water.
I have a question. Actually, I know the answer, but I want to trip up my BIL the next time he makes a claim.
Is it true that if you repeatedly drop a magnet, over time it will lose its magnetic capabilities?
It might. Depends on the specific material of the magnet, of course, but most common metallic permanent magnets will weaken or lose their magnetism altogether if dropped or otherwise shocked often and hard enough. Ceramic magnets are more likely to break first.
But not necessarily permanently. Some, like the aforementioned transformer core materials, will only remain strongly magnetized in the presence of an externally applied field. Take the field away, and these materials retain very little, if any, magnetism.
That would be “very little”. But even transformer-core alloys will retain some trace history. I’d be willing to bet that if you sat a transformer core in a multi-Tesla field for an hour, that when you took it out you’d be able to pick up paper clips with it. Not so, for a true paramagnet.
And I don’t think that dropping a magnet will cause it to lose magnetization “over time”; each drop will either de-magnetize it or it won’t. Do it enough times, and it’s a pretty safe bet that you’ll get it, but that’s just a matter of the odds catching up to you, not a cumulative effect.
Why? how does dropping a magnet affect it’s field?
The physical shock causes realignment of the magnetic domains (which may be atoms, molecules or larger grain structures, depending on the material); how much realignment occurs depends on factors like the structure of the magnetic domains and the degree and direction of the shock:
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translation, a magnetic piece of steel and a nonmagnetic only differ in one basic way
non magnetic the molecules are pointing in random directions, in a magnet the all point the same way. drop it and some will start to point in other directions, keep dropping it and it will lose a lot of power as more and more molecules stop pointing in the same direction.
So what’s a “keeper” for a magnet? IIRC I had a fairly powerful magnet (for a kid 
) that lost its magnetism when my little sister lost the little strip of metal that sat across the ends of the magnet.
A “keeper” allows a greater magnetic flux to flow through the magnet, so that the field intensity in the magnet is greater and the zillions of tiny poles inside prefer to remain aligned. For some magnets such as steel and Alnico, keepers help prolong the life. But many magnets such as neodymium-iron-boron don’t need keepers.
Crap. He was right.