Exact eigenstates of highly frustrated spin lattices probed in high fields

Abstract

Strongly frustrated antiferromagnets such as the magnetic molecule {Mo72Fe30}, the kagome, or the pyrochlore lattice exhibit a variety of fascinating properties like low-lying singlets, magnetization plateaus as well as magnetization jumps. During recent years exact many-body eigenstates could be constructed for several of these spin systems. These states become ground states in high magnetic fields, and they also lead to exotic behavior. A key concept to an understanding of these properties is provided by independent localized magnons. The energy eigenvalue of these n-magnon states scales linearly with the number n of independent magnons and thus with the total magnetic quantum number M=Ns-n. In an applied field this results in a giant magnetization jump which constitutes a new macroscopic quantum effect. It will be demonstrated that this behavior is accompanied by a massive degeneracy, an extensive (T=0)-entropy, and thus a large magnetocaloric effect at the saturation field. The connection to flat band ferromagnetism will be outlined.

4 pages, submitted to the proceedings of the Yamada Conference LX on Research in High Magnetic Fields, August 16-19, 2006 Sendai, Japan

References in corpus (4)

• Exact low-temperature behavior of kagome antiferromagnet at high fields
• Magnetocaloric effect in one-dimensional antiferromagnets
• Exact eigenstates and macroscopic magnetization jumps in strongly frustrated spin lattices
• Universal low-temperature behavior of frustrated quantum antiferromagnets in the vicinity of the saturation field

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• Magnetization process and ordering of the $S=1/2$ pyrochlore magnet in a field
• Spin-wave spectra of a kagome stripe
• $\mathbf{\Delta }$S${}^z$=2 quantum magnetization discontinuities proportional in number to the spin s in C${}_{60}$: Origin and the role of symmetry
• Origin of the classical magnetization discontinuities of the dodecahedron