helimagnetism

helimagnetism [‚hel·ə′mag·nə‚tiz·əm]

(solid-state physics)

A property possessed by some metals, alloys, and salts of transition elements or rare earths, in which the atomic magnetic moments, at sufficiently low temperatures, are arranged in ferromagnetic planes, the direction of the magnetism varying in a uniform way from plane to plane.

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Helimagnetism

A property possessed by some metals, alloys, and salts of transition elements in which the atomic magnetic moments, at sufficiently low temperatures, are arranged in a spiral or helix. Simple antiferromagnets and ferromagnets can be considered as nonconical helimagnets with helical angles of 180 and 0°, respectively. In the same way, nonconical helimagnets may be considered as conical helimagnets with cone angle of 0°. Some typical helimagnets are listed in the table. The magnetic structures have been detected by neutron diffraction.

Some representative helimagnets

Substance	Magnetic structure	Temperature, K
MnO2	Nonconical helix	0 < T < 84
MnAu2	Nonconical helix	0 < T < 363
Dy	Nonconical helix	85 < T < 179
	Ferromagnet	0 < T < 85
MnCr2O4	Simple ferrimagnet	18 < T < 43
	Complex conical helix	0 < T < 18
Er	Conical helix	0 < T < 20
	Complex oscillation	20 < T < 53
	Sinusoidal antiferromagnet	53 < T < 85