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@PHDTHESIS{Wang:893045,
      author       = {Wang, Xiao},
      title        = {{S}ingle crystal growth and neutron scattering studies of
                      novel quantum materials},
      volume       = {239},
      school       = {RWTH Aachen},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2021-02523},
      isbn         = {978-3-95806-546-8},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {VI, 145 S.},
      year         = {2021},
      note         = {Dissertation, RWTH Aachen, 2021},
      abstract     = {The recent development of theoretical and experimental
                      study of emergent phenomena, such as anomalous Hall effects,
                      topological electronic band structures as well as quantum
                      spin liquid states in condensed matter physics have evoked
                      tremendous research interest in the search and study of
                      novel quantum materials. High quality single crystal samples
                      of the quantum materials, which serve as a key prerequisite
                      to study the novel properties are of great importance in the
                      study of quantum materials. In this PhD work, employing two
                      cutting-edge methods: molten flux and chemical vapour
                      transport, series of novel quantum material single high
                      quality crystal samples have been grown, such as CeSb, PrSb,
                      NdSb, $\alpha$-RuCl$_{3}$, Mn$_{3}$Sn,Sr$_{2}$IrO$_{4}$,
                      Cr$_{2}$Ge$_{2}$Te$_{6}$, Cr$_{2}$Si$_{2}$Te$_{6}$,
                      CeZn$_{3}$As$_{3}$, PrZn$_{3}$As$_{3}$, PtBi$_{2}$,
                      ZrTe$_{5}$, which have been studied intensively in this PhD
                      work as well as other cooperators. The second important part
                      of this PhD thesis is to study the correlation among crystal
                      structure, magnetic structure and physical properties in two
                      novel quantum materials: Mn$_{3}$Sn and $\alpha$-RuCl$_{3}$
                      by comprehensive characterization methods. Mn$_{3}$Sn, which
                      is proposed to be a candidate of magnetic Weyl semimetal has
                      been studied by a combination of polarised and unpolarised
                      neutron diffraction techniques in this work. Single crystals
                      of topological semimetal Mn$_{3}$Sn have been grown by Sn
                      self-flux method. The magnetic susceptibility and electronic
                      resistivity showed a magnetic phase transition at 285K and
                      below that, the anomalous Hall effects at room temperature
                      disappeared completely. With a combination of unpolarised
                      and polarised neutron study, the crystal structure and
                      magnetic structure at low temperature have been determined
                      and a novel double-q magnetic ground state is found. As a
                      result of breaking symmetry, AHE could not be realised in
                      this kind of magnetic structure but the double-q magnetic
                      structure has offered a rare case to study the non coplanar
                      order in materials with kagomé lattice.a-RuCl3, which is a
                      candidate to realise Kitaev quantum spin liquid, is a
                      layered two dimensional materials bonded with the weak Van
                      der Weals force. Growing high quality samples of
                      a-RuCl$_{3}$ single crystals has been a big challenge since
                      the stacking faults will be introduced inevitably. In this
                      thesis, single crystals up to 700 mg were successfully grown
                      by optimising the crystal growth conditions. Based on the
                      high quality single crystals, the low temperature crystal
                      structure of a-RuCl$_{3}$ has been proved to be
                      R$\overline{3}$ instead of C2/$\textit{m}$ by single crystal
                      neutron diffraction which demonstrates that a-RuCl$_{3}$
                      maybe a perfect candidate to study Kitaev physics without
                      lattice distortion. Besides, with spherical polarised
                      neutron analysis the ordered magnetic moment direction of
                      Ru3$^{+}$ has been precisely determined which will help to
                      reveal the microscopic interaction in Kitaev quantum spin
                      liquids physics. In addition, the phase diagram of
                      a-RuCl$_{3}$ under isostatic pressures has also been
                      determined by single crystal neutron diffraction. The
                      results reveal the magnetic order in a-RuCl$_{3}$ could be
                      effectively suppressed with increase of external hydrostatic
                      pressure. However, a pressure induced structural phase
                      transition occurs when the pressure is higher than 0.15 GPa.
                      Despite that the quantum spin liquid state is not realised
                      in a-RuCl$_{3}$ by the isostatic pressure, this result has
                      proved that the pressure could change the transition
                      temperature in Kitaev materials explicitly and will shed
                      lights on the pressure tuning magnetic order in similar
                      materials.},
      cin          = {JCNS-4 / JCNS-FRM-II / JCNS-2 / MLZ},
      cid          = {I:(DE-Juel1)JCNS-4-20201012 /
                      I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-2-20110106 / I:(DE-588b)4597118-3},
      pnm          = {6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ)
                      (POF4-6G4) / 632 - Materials – Quantum, Complex and
                      Functional Materials (POF4-632)},
      pid          = {G:(DE-HGF)POF4-6G4 / G:(DE-HGF)POF4-632},
      experiment   = {EXP:(DE-MLZ)DNS-20140101 / EXP:(DE-MLZ)HEIDI-20140101 /
                      EXP:(DE-Juel1)ILL-IN12-20150421},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/893045},
}