Magnetization and spin dynamics of the spin S=12 hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O

R. Nath, A. A. Tsirlin, P. Khuntia, O. Janson, T. Förster, M. Padmanabhan, J. Li, Yu Skourski, M. Baenitz, H. Rosner, I. Rousochatzakis

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Abstract

We report a combined experimental and theoretical study of the spin S=12 nanomagnet Cu5(OH)2(NIPA)4·10H 2O (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 a microscopic magnetic 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=12 doublet ground state (GS), with an exactly vanishing zero-field splitting (by Kramers' theorem), and a very large excitation gap of Δ≠68 K. Thus, Cu5-NIPA is a good candidate for achieving long electronic spin relaxation (T1) and coherence (T2) 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=12 nanomagnet showing an enhancement in the nuclear spin-lattice relaxation rate 1/T1 at intermediate temperatures.

Original languageEnglish
Article number214417
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number21
DOIs
Publication statusPublished - Jun 14 2013

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Nath, R., Tsirlin, A. A., Khuntia, P., Janson, O., Förster, T., Padmanabhan, M., Li, J., Skourski, Y., Baenitz, M., Rosner, H., & Rousochatzakis, I. (2013). Magnetization and spin dynamics of the spin S=12 hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O. Physical Review B - Condensed Matter and Materials Physics, 87(21), [214417]. https://doi.org/10.1103/PhysRevB.87.214417