antiferromagnetically

Antiferromagnetically is an adverb describing the manner in which magnetic moments in a material orient themselves in an antiferromagnet. In such materials, neighboring atomic spins align in opposite directions due to exchange interactions, resulting in little or no net macroscopic magnetization under normal conditions. The term is used to describe both the orientation of spins and the response of the system to external stimuli when the interaction is antiferromagnetic.

Antiferromagnetic order typically emerges below a characteristic Néel temperature. The simplest description uses the Heisenberg model with an exchange coupling J<0, favoring antiparallel alignment on neighboring sites. Real materials may exhibit noncollinear or canted order due to anisotropy, defects, or external fields, which can produce a small residual magnetization.

Techniques such as neutron diffraction detect antiferromagnetic ordering; magnetic susceptibility follows a Curie-Weiss law with a negative Weiss constant in the high-temperature paramagnetic phase. Common antiferromagnets include transition metal oxides such as MnO, FeO, NiO, and Cr2O3; layered or doped systems show complex order, including spin-flop transitions under applied magnetic fields.

Antiferromagnetic materials are important in spintronics, for exchange bias in spin valves, and as reference layers in magnetic sensors; their lack of stray fields offers advantages for device scaling, though control of antiferromagnetic order is technologically challenging.