Magnetization and spin dynamics of the spin S = ½ hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O
Magnetization and spin dynamics of the spin S = ½ hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O
Nath, R.; Tsirlin, A. A.; Khuntia, P.; Janson, O.; Förster, T.; Padmanabhan, M.; Li, J.; Skourski, Y.; Baenitz, M.; Rosner, H.; Rousochatzakis, I.
Abstract
We report a combined experimental and theoretical study of the spin S = ½ nanomagnet Cu5(OH)2(NIPA)4·10H2O (Cu5-NIPA). Using thermodynamic, electron spin resonance, and 1H nuclear magnetic resonance measurements on one hand, and ab initio density-functional band-structure calculations, exact diagonalizations, and a strong-coupling theory on the other, we derive amicroscopicmagnetic model of Cu5-NIPA and characterize the spin dynamics of this system. The elementary fivefold Cu2+ unit features an hourglass structure of two corner-sharing scalene triangles related by inversion symmetry. Our microscopic Heisenberg model comprises one ferromagnetic and two antiferromagnetic exchange couplings in each triangle, stabilizing a single spin S = ½ doublet ground state (GS), with an exactly vanishing zero-field splitting (by Kramers’ theorem), and a very large excitation gap of ∆ ≈ 68 K. Thus, Cu5-NIPA is a good candidate for achieving long electronic spin relaxation (T
1) and coherence (T
2) times at low temperatures, in analogy to other nanomagnets with low-spin GS’s. Of particular interest is the strongly inhomogeneous distribution of the GS magnetic moment over the five Cu2+ spins. This is a purely quantum-mechanical effect since, despite the nonfrustrated nature of the magnetic couplings, the GS is far from the classical collinear ferrimagnetic configuration. Finally, Cu5-NIPA is a rare example of a S = ½ nanomagnet showing an enhancement in the nuclear spin-lattice relaxation rate 1/T
1 at intermediate temperatures.
Beteiligte Forschungsanlagen
- Hochfeld-Magnetlabor (HLD)
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Physical Review B 87(2013)21, 214417
DOI: 10.1103/PhysRevB.87.214417
Cited 20 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-19412