Curie temp?

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The Curie temperature is a point at which materials lose their ferromagnetism, the ability to align their atoms even in the absence of a magnetic field. They become paramagnetic, requiring an external magnetic field to magnetize and stay in that state. Magnetic materials can change properties at a variety of temperatures, but they are often quite high. When the temperature drops again, the material recovers its magnetism, proving that the phase change is reversible. The Curie temperature phenomenon is named after the well-known researcher Pierre Curie.

When materials are in a ferromagnetic state, exposure to a magnetic field can align their atoms and create an attraction. If the field is removed, the magnetism remains, as the material has a form of memory. This can be used to create permanent magnets and demonstrate a variety of interesting physical phenomena. Paramagnetic materials, however, require an external magnetic field to be maintained in order to remain magnetized.

At the Curie temperature, the heat agitates the atoms within the material so much that they can’t line up and it loses its magnetism. This can have important implications. In geology, for example, high heat can occur in lightning and volcanic eruptions and can change the properties of minerals in the earth’s crust. Observers looking at magnetic minerals need to consider their history and what might have influenced them.

This can also be important for magnetic materials used in high heat environments. If the temperature gets too high, they can lose their properties and may not work as intended. A simple example is sometimes used for demonstrations in science lessons, where a teacher demonstrates how heating above the Curie temperature causes a paper clip or similar metal object to lose its attraction to a magnet. In a situation where magnetic attraction could be relied upon for a process or function, it would not be desirable to reach the Curie temperature.

Data sheets on the properties of ferromagnetic and ferrimagnetic materials discuss their Curie temperatures. This information is provided for reference, so people know how materials should behave in response to changes in temperature. For companies that prepare products, it can be especially important to have technical specifications on the materials used, so they can plan the design and operate accordingly. If a material loses its magnetic attraction under normal use, the company may need to choose a different material to use in manufacturing.

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