Heisenberg spin triangles in {V6}-type magnetic molecules: Experiment and theory

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Luban, Marshall
Borsa, Ferdinando
Bud'ko, Sergey
Jun, Suckjoon
Jung, Jae Kap
Kögerler, Paul
Mentrup, Detlef
Müller, Achim
Modler, Robert
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Canfield, Paul
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Ames National Laboratory

Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.

For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.

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We report the results of systematic experimental and theoretical studies of two closely related species of magnetic molecules of the type {V6}, where each molecule includes a pair of triangles of exchange-coupled vanadyl (VO2+,spin s=1/2) ions. The experimental studies include the temperature dependence of the low-field susceptibility from room temperature down to 2 K, the dependence of the magnetization on magnetic field up to 60 T for several low temperatures, the temperature dependence of the magnetic contribution to the specific heat, and the 1H and 23Nanuclear magnetic resonance spin-lattice relaxation rates 1/T1. This body of experimental data is accurately reproduced for both compounds by a Heisenberg model for two identical uncoupled triangles of spins; in each triangle, the spins interact via isotropic antiferromagnetic exchange, where two of the three V-V interactions have exchange constants that are equal and an order of magnitude larger than the third; the ground-state eigenfunction has total spin quantum number S=1/2 for magnetic fields below a predicted critical field Hc≈74T and S=3/2 for fields above Hc.


This article is from Physical Review B 66 (2002): 054407, doi:10.1103/PhysRevB.66.054407. Posted with permission.

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