antiferromagnetické

Antiferromagnetism is a form of magnetic ordering that occurs in certain materials below a specific temperature known as the Néel temperature. In an antiferromagnetic material, the magnetic moments of neighboring atoms align in an antiparallel fashion. This means that for every magnetic moment pointing in one direction, there is an adjacent magnetic moment pointing in the opposite direction.

Unlike ferromagnetic materials, where all magnetic moments align parallel to create a net macroscopic magnetization, the antiparallel alignment in antiferromagnets results in a zero net magnetic moment at the atomic level. Consequently, antiferromagnetic materials do not exhibit spontaneous magnetization and are therefore not attracted to external magnets in the same way that ferromagnetic materials are.

The Néel temperature, denoted as $T_N$, is a critical parameter for antiferromagnetic substances. Above this temperature, thermal agitation overcomes the exchange interactions that favor antiparallel alignment, and the material behaves paramagnetically. Below $T_N$, the magnetic ordering sets in.

Examples of antiferromagnetic materials include chromium, manganese oxide, and nickel oxide. While they don't produce a strong external magnetic field, antiferromagnetic materials are important in various technological applications, particularly in spintronics and magnetic storage devices, where their unique magnetic properties can be exploited for data manipulation and reading. Their study is a significant area within condensed matter physics.