Antiferromagnetic ordering

In materials that exhibit antiferromagnetism, the spins of electrons align in a regular pattern with neighboring spins pointing in opposite directions. This is a different manifestation of magnetism. Generally, antiferromagnetic materials exhibit antiferromagnetism at a low temperature, and become disordered above a certain temperature; the transition temperature is called the Néel temperature. Above the Néel temperature, the material is typically paramagnetic. Image File history File links Antiferromagnetic_ordering. ... Image File history File links Antiferromagnetic_ordering. ... For other uses, see Electron (disambiguation). ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... For other senses of this word, see magnetism (disambiguation). ... ... Simple Illustration of a paramagnetic probe made up from miniature magnets. ...

The antiferromagnetic behaviour at low temperature usually results in diamagnetic properties, but can sometimes display ferrimagnetic behaviour, which in many physically observable properties is more similar to ferromagnetic interactions. Diamagnetism is a very weak form of magnetism that is only exhibited in the presence of an external magnetic field. ... A ferrimagnetic interaction is a specific type of antiferromagnetic interaction in which the net spin of the system is not equal to zero due to the spin in each direction not being equal, and therefore not cancelling. ...

The magnetic susceptibility of an antiferromagnetic material will appear to go through a maximum as the temperature is lowered; in contrast, that of a paramagnet will continually increase with decreasing temperature. Simple Illustration of a paramagnetic probe made up from miniature magnets. ...

Antiferromagnetic materials have low geometrical frustration, and a negative coupling between adjacent moments. Geometrical frustration is a phenomenon in condensed matter physics in which the geometrical properties of the atomic lattice forbid the existence of a unique ground state. ...

Antiferromagnetic materials are relatively uncommon. An example is the heavy-fermion superconductor URu₂Si₂. More everyday examples include metals such as chromium, alloys such as iron manganese (FeMn), and oxides such as nickel oxide (NiO). There are also numerous examples among high nuclearity metal clusters. Organic molecules can also exhibit antiferromagnetic coupling under rare circumstances, as seen in radicals such as 5-dehydro-m-xylylene. General Name, symbol, number chromium, Cr, 24 Chemical series transition metals Group, period, block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... 5-dehydro-m-xylylene, or DMX is an organic triradical molecule which violates Hunds Rule. ...

Antiferromagnets can also couple to ferromagnetic materials through a mechanism known as exchange anisotropy, in which the ferromagnetic film is either grown upon the antiferromagnet or annealed in an aligning magnetic field, causing the surface atoms of the ferromagnet to align with the surface atoms of the antiferromagnet. This provides the ability to "pin" the orientation of a ferromagnetic film, which provides one of the main uses in so-called spin valves, which are the basis of magnetic sensors including modern hard drive read heads. Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... Exchange bias or exchange anisotropy occurs in bilayers (or multilayers) of magnetic materials where the hard magnetization behavior of an antiferromagnetic thin film causes a shift in the soft magnetization curve of a ferromagnetic film. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... A spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance (from low to high or high to low) depending on the alignment of the magnetic layers. ... Typical hard drives of the mid-1990s. ...

There are also examples of disordered materials (such as iron phosphate glasses) that become antiferromagnetic below their Néel temperature. These disordered networks 'frustrate' the antiparallelism of adjacent spins; i.e. it is not possible to construct a network where each spin is surrounded by opposite neighbour spins. It can only be determined that the average correlation of neighbour spins is antiferromagnetic. This type of magnetism is termed 'speromagnetism'.

See also

• Exchange bias
• Geometrically frustrated magnet