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Some antiferromagnetic
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring Spin (physics), spins (on different sublattices) pointing in oppos ...
materials exhibit a non-zero magnetic moment
In electromagnetism, the magnetic moment or magnetic dipole moment is the combination of strength and orientation of a magnet or other object or system that exerts a magnetic field. The magnetic dipole moment of an object determines the magnitude ...
at a temperature near absolute zero
Absolute zero is the lowest possible temperature, a state at which a system's internal energy, and in ideal cases entropy, reach their minimum values. The absolute zero is defined as 0 K on the Kelvin scale, equivalent to −273.15 ° ...
. This effect is ascribed to spin canting, a phenomenon through which spins are tilted by a small angle about their axis rather than being exactly co-parallel.
Spin canting is due to two factors contrasting each other: isotropic exchange would align the spins exactly antiparallel, while antisymmetric exchange arising from relativistic effects ( spin–orbit coupling) would align the spins at 90° to each other. The net result is a small perturbation, the extent of which depends on the relative strength of these effects.
This effect is observable in many materials such as hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
.
References
{{reflist Magnetic ordering Spintronics