### Abstract

We report a combined experimental and theoretical study of the spin S=12 nanomagnet Cu_{5}(OH)_{2}(NIPA)_{4}·10H _{2}O (Cu_{5}-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 Cu_{5}-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 Δâ‰ 68 K. Thus, Cu_{5}-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, Cu_{5}-NIPA is a rare example of a S=12 nanomagnet showing an enhancement in the nuclear spin-lattice relaxation rate 1/T_{1} at intermediate temperatures.

Original language | English |
---|---|

Article number | 214417 |

Journal | Physical Review B - Condensed Matter and Materials Physics |

Volume | 87 |

Issue number | 21 |

DOIs | |

Publication status | Published - Jun 14 2013 |

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### ASJC Scopus subject areas

- Condensed Matter Physics
- Electronic, Optical and Magnetic Materials

### Cite this

*Physical Review B - Condensed Matter and Materials Physics*,

*87*(21), [214417]. https://doi.org/10.1103/PhysRevB.87.214417

**Magnetization and spin dynamics of the spin S=12 hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O.** / Nath, R.; Tsirlin, A. A.; Khuntia, P.; Janson, O.; Förster, T.; Padmanabhan, M.; Li, Jing; Skourski, Yu; Baenitz, M.; Rosner, H.; Rousochatzakis, I.

Research output: Contribution to journal › Article

*Physical Review B - Condensed Matter and Materials Physics*, vol. 87, no. 21, 214417. https://doi.org/10.1103/PhysRevB.87.214417

}

TY - JOUR

T1 - Magnetization and spin dynamics of the spin S=12 hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O

AU - Nath, R.

AU - Tsirlin, A. A.

AU - Khuntia, P.

AU - Janson, O.

AU - Förster, T.

AU - Padmanabhan, M.

AU - Li, Jing

AU - Skourski, Yu

AU - Baenitz, M.

AU - Rosner, H.

AU - Rousochatzakis, I.

PY - 2013/6/14

Y1 - 2013/6/14

N2 - 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 Δâ‰ 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.

AB - 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 Δâ‰ 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.

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U2 - 10.1103/PhysRevB.87.214417

DO - 10.1103/PhysRevB.87.214417

M3 - Article

AN - SCOPUS:84879991695

VL - 87

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 21

M1 - 214417

ER -