antiferromagnetische

Antiferromische, or antiferromagnetism, refers to a type of magnetic order in which neighboring atomic spins align in opposite directions. In an antiferromagnet, the exchange interaction between adjacent magnetic moments favors antiparallel alignment, so the net magnetization cancels out in zero external field. In many materials the lattice is bipartite, consisting of two interpenetrating sublattices whose moments are roughly equal in magnitude but oppositely oriented.

Below a characteristic temperature, the Néel temperature (TN), long-range antiferromagnetic order emerges. Above TN the material is paramagnetic and shows Curie–Weiss-like behavior; the magnetic susceptibility decreases with increasing temperature.

The response to external magnetic fields is distinctive: the net moment remains small until high fields, and a spin-flop or spin-flip transition can reorient spins, often resulting in a larger net magnetization along the field.

Common antiferromagnets include transition-metal oxides such as MnO, NiO, FeF2, CoO, Cr2O3, and certain perovskites. Antiferromagnetic order also arises in some metals and itinerant systems with complex spin structures, including spin-density waves.

Dynamics: spin waves (magnons) in antiferromagnets have two branches due to two sublattices; they are typically gapped by anisotropy and can reach THz frequencies, enabling ultrafast spin dynamics.

Applications: Antiferromagnetic materials are robust against external magnetic fields, used in exchange bias to pin ferromagnetic layers, and are central to emerging antiferromagnetic spintronics, where information is encoded in the antiferromagnetic order and manipulated by spin currents or ultrafast optical pulses. In German-language contexts the term antiferromische Ordnung is used to describe this phenomenon.