paramagnetism
/ PAIR-uh-mag-net-iz-um /
Imagine a room full of tiny compass needles, each free to spin but jostled constantly by heat so they all point randomly. On average they cancel and the room shows no magnetism. Switch on a strong field and they all try to line up, giving a weak net magnetism that vanishes the moment you switch off. That is paramagnetism: a weak attraction that only exists while the field is on.
The difference from diamagnetism is that a paramagnetic atom has a permanent moment of its own, usually from unpaired electrons, but these moments are not coupled to each other. Left alone they point every which way because thermal energy keeps knocking them around. An applied field nudges a small excess of them into alignment, giving a small positive susceptibility, roughly 10^-5 to 10^-3. Because heat fights the alignment, paramagnets get weaker as they warm up: the magnetization follows the Curie law, magnetization proportional to field divided by temperature.
Aluminum, titanium, magnesium, and gaseous oxygen are paramagnetic, which is why liquid oxygen poured between the poles of a strong magnet visibly clings there. Paramagnetism matters as a baseline and as a clue: measuring susceptibility tells chemists how many unpaired electrons an ion has. It is also the state a ferromagnet falls back to above its Curie temperature, once heat has broken the coupling that made the moments cooperate.
Liquid oxygen, which is paramagnetic, visibly bridges and sticks between the poles of a strong magnet until it boils away.
Permanent atomic moments align weakly with a field, but heat randomizes them again.
Paramagnetism needs the field to stay on; remove it and thermal agitation randomizes the moments so the net magnetization drops back to zero, unlike a ferromagnet that stays magnetized.