How does temperature affect magnetism in materials?

Temperature can affect magnetism in materials by altering their magnetic properties, often reducing their magnetism as temperature increases.

In more detail, the relationship between temperature and magnetism is quite complex. It's all about the alignment of magnetic domains within a material. In a magnetised material, the magnetic domains are aligned in the same direction. However, as the temperature increases, the thermal energy also increases. This added energy can cause the magnetic domains to move around and become misaligned, which weakens the magnetic field of the material.

This is particularly noticeable in ferromagnetic materials, such as iron, nickel, and cobalt. These materials are strongly magnetic because their magnetic domains are naturally aligned. But when they are heated to a certain temperature, known as the Curie temperature, they lose their magnetism completely. This is because the thermal energy is so high that the magnetic domains can't stay aligned. Once the material cools down, the domains can realign and the material becomes magnetic again.

In contrast, paramagnetic materials, like aluminium and platinum, are only weakly magnetic and their magnetism increases slightly with temperature. This is because the thermal energy helps to align their magnetic domains. However, the effect is very small and usually not noticeable.

In summary, temperature can have a significant effect on the magnetism of a material. For ferromagnetic materials, increasing temperature can reduce their magnetism, and can even eliminate it at high enough temperatures. For paramagnetic materials, the effect is much less pronounced, but there can be a slight increase in magnetism with temperature.