Heating a magnet past a certain temperature makes it stop being a magnet

A bar magnet feels permanent. It is not. Heat one hot enough and the magnetism simply quits. The threshold has a name: the Curie temperature, after physicist Pierre Curie, who studied how heat erodes magnetism in the 1890s.

The reason lives at the atomic scale. In iron, nickel, or cobalt, each atom behaves like a tiny compass needle, and below the Curie point neighboring atoms lock into aligned regions called domains. That shared alignment is what makes the bulk material magnetic. As you add heat, the atoms jostle harder. Push past the Curie temperature and, as Georgia State’s HyperPhysics puts it, “the ferromagnetic property disappears as a result of thermal agitation” — the long-range order collapses all at once and the material turns paramagnetic, barely magnetic at all.

Below the line, atoms march in step. Above it, thermal chaos wins and the magnetism evaporates.

The numbers are specific to each metal. Iron loses its magnetism at about 770 °C (1,043 K); nickel gives up far earlier, near 354 °C, and cobalt holds out to roughly 1,115 °C. A fridge magnet’s neodymium alloy quits around 320 °C.

The best part: it is reversible. Cool the metal back below its Curie point and the domains realign, the magnetism returning as if nothing happened. It is one of physics’ cleanest phase transitions — a property that flips off and on with nothing but temperature.