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a phenomenon in ferrites where there can be incomplete cancellation of antiferromagnetic arranged spins giving a net magnetic moment

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/07 11:01:08」(JST)

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Not to be confused with Ferromagnetism; for an overview see Magnetism

Ferrimagnetic ordering

In physics, a ferrimagnetic material is one in which the magnetic moments of the atoms on different sublattices^{[clarification needed]} are opposed, as in antiferromagnetism; however, in ferrimagnetic materials, the opposing moments are unequal and a spontaneous magnetization remains.^[1] This happens when the sublattices consist of different materials or ions (such as Fe²⁺ and Fe³⁺).

Ferrimagnetism is exhibited by ferrites and magnetic garnets. The oldest known magnetic substance, magnetite (iron(II,III) oxide; Fe₃O₄), is a ferrimagnet; it was originally classified as a ferromagnet before Néel's discovery of ferrimagnetism and antiferromagnetism in 1948.^[2]

Some ferrimagnetic materials are YIG (yttrium iron garnet) and ferrites composed of iron oxides and other elements such as aluminum, cobalt, nickel, manganese and zinc.

Effects of temperature[edit source | edit]

➀ Below the magnetization compensation point, ferrimagnetic material is magnetic. ➁ At the compensation point, the magnetic components cancel each other and the total magnetic moment is zero. ➂ Above the Curie point, material loses magnetism.

Ferrimagnetic materials are like ferromagnets in that they hold a spontaneous magnetization below the Curie temperature, and show no magnetic order (are paramagnetic) above this temperature. However, there is sometimes a temperature below the Curie temperature at which the two sublattices have equal moments, resulting in a net magnetic moment of zero; this is called the magnetization compensation point. This compensation point is observed easily in garnets and rare earth - transition metal alloys (RE-TM). Furthermore, ferrimagnets may also exhibit an angular momentum compensation point at which the angular momentum of the magnetic sublattices is compensated. This compensation point is a crucial point for achieving high speed magnetization reversal in magnetic memory devices.^[3]

Properties[edit source | edit]

Ferrimagnetic materials have high resistivity and have anisotropic properties. The anisotropy is actually induced by an external applied field. When this applied field aligns with the magnetic dipoles it causes a net magnetic dipole moment and causes the magnetic dipoles to precess at a frequency controlled by the applied field, called Larmor or precession frequency. As a particular example, a microwave signal circularly polarized in the same direction as this precession strongly interacts with the magnetic dipole moments; when it is polarized in the opposite direction the interaction is very low. When the interaction is strong, the microwave signal can pass through the material. This directional property is used in the construction of microwave devices like isolators, circulators and gyrators. Ferrimagnetic materials are also used to produce optical isolators and circulators.

Molecular ferrimagnets[edit source | edit]

Ferrimagnetism can also occur in molecular magnets. A classic example is a dodecanuclear Manganese molecule with an effective spin of S = 10 derived from antiferromagnetic interaction on Mn(IV) metal centres with Mn(III) and Mn(II) metal centres.^[4]

References[edit source | edit]

^ Spaldin, Nicola A. (2010). "9. Ferrimagnetism". Magnetic materials : fundamentals and applications (2nd ed.). Cambridge: Cambridge University Press. pp. 113–129. ISBN 9780521886697.
^ L. Néel, Propriétées magnétiques des ferrites; Férrimagnétisme et antiferromagnétisme, Annales de Physique (Paris) 3, 137-198 (1948).
^ C. D. Stanciu, A. V. Kimel, F. Hansteen, A. Tsukamoto, A. Itoh, A. Kirilyuk, and Th. Rasing, Ultrafast spin dynamics across compensation points in ferrimagnetic GdFeCo: The role of angular momentum compensation, Phys. Rev. B 73, 220402(R) (2006).
^ Sessoli, Roberta; Tsai, Hui Lien ; Schake, Ann R. ; Wang, Sheyi; Vincent, John B.; Folting, Kirsten; Gatteschi, Dante; Christou, George; Hendrickson, David N. (1993). "High-spin molecules: [Mn₁₂O₁₂(O₂CR)₁₆(H₂O)₄]". J. Am. Chem. Soc., 115 (5): 1804–1816. doi:10.1021/ja00058a027.

English Journal

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Direct interactions between nanoparticles of Mn-doped magnetite or maghemite (clearly differentiated by Raman spectroscopy) grouped in spherical clusters minimize the effect related to their characteristic magnetic dead layer at the surface. Hence, the clustering process jointly with the manganese d
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In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn7) to nonadecamer (Mn19) satisfying the relation 1 + Σn6n, where n is the ring number of the Brucite structure
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Controlled Phase and Tunable Magnetism in Ordered Iron Oxide Nanotube Arrays Prepared by Atomic Layer Deposition.

Zhang Y1, Liu M1,2, Peng B1, Zhou Z3, Chen X3, Yang SM2,4, Jiang ZD2,4, Zhang J1, Ren W1,2, Ye ZG1,2,5.
Scientific reports.Sci Rep.2016 Jan 27;6:18401. doi: 10.1038/srep18401.
Highly-ordered and conformal iron oxide nanotube arrays on an atomic scale are successfully prepared by atomic layer deposition (ALD) with controlled oxidization states and tunable magnetic properties between superparamagnetism and ferrimagnetism. Non-magnetic α-Fe2O3 and superparamagnetic Fe3O4 wi
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