## Theory of the Nuclear Magnetic 1/T1 Relaxation Rate in Conventional and Unconventional MagnetsOne of the best ways to "lift the lid" on what is happening inside a given material is to study it using nuclear magnetic resonance (NMR). Of particular interest are NMR 1/T1 relaxation rates, which measure how fast energy stored in magnetic nuclei is transferred to surrounding electrons. This thesis develops a detailed, quantitative theory of NMR 1/T1 relaxation rates, and shows for the first time how they could be used to measure the speed at which energy travels in a wide range of magnetic materials. This theory is used to make predictions for"Quantum Spin Nematics", an exotic form of quantum order analogous to a liquid crystal. In order to do so, it is first necessary to unravel how spin nematics transport energy. This thesis proposes a new way to do this, based on the description of quarks in high-energy physics. Experiments to test the ideas presented are now underway in laboratories across the world. |

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### Contents

1 | |

The Néel Antiferromagnet | 31 |

A Theory of the 1T1 Relaxation Rate in Magnetic Systems | 49 |

4 Theory of the NMR Relaxation Rate in Magnetic Fepnictides | 58 |

The 3Sublattice Antiferroquadrupolar State | 83 |

The 2Sublattice Antiferroquadrupolar State | 113 |

7 How to Recognise the Quantum SpinNematic State Using NMR | 137 |

8 Conclusion and Outlook | 149 |

A Calculation of the Longitudinal Suceptibility Relevant to BaFe2As2 | 153 |

B Spectral Representations of Form Factors | 158 |

C Integrating Products of Bose Functions | 161 |

D The Form Factor for 7Li NMR in the SpinNematic State | 162 |

### Other editions - View all

Theory of the Nuclear Magnetic 1/T1 Relaxation Rate in Conventional and ... Andrew Smerald No preview available - 2015 |

Theory of the Nuclear Magnetic 1/T1 Relaxation Rate in Conventional and ... Andrew Smerald No preview available - 2013 |

Theory of the Nuclear Magnetic 1/T1 Relaxation Rate in Conventional and ... Andrew Smerald No preview available - 2013 |

### Common terms and phrases

1/T1 relaxation rate 2-sublattice AFQ AFQ order angle-resolved antiferromagnetic antiferroquadrupolar AFQ approximation associated BaFe2 BaFe2As2 bond-centred bonds boson Brillouin zone calculated canting field collinear continuum theory degrees of freedom describe dipole directors dispersion dynamic spin susceptibility dynamic susceptibility electron energy experimental external field ferromagnetic field applied field theory flavour-wave form factor frustrated magnets gapless gapped Goldstone modes Hamiltonian Heisenberg model hext hnuc inelastic neutron scattering Lett LiCuVO4 low temperatures low-energy magnetic excitations magnetic field magnetic order microscopic model Mila Momoi nearest-neighbour Néel antiferromagnet nematic nematic order NLSM NMR 1/T1 relaxation non-linear sigma model order parameter ordering vector orientation paramagnet partition function phase transition Phys physical quadrupolar quadrupole quantitative quantum spin-nematic rotations Shannon shown in Fig Smerald spin fluctuations spin wave spin-dipole spin-nematic order spin-wave excitations square lattice sublattices symmetry tensor theoretical thesis three-sublattice triangular lattice two-sublattice Unconventional Magnets