% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Maraytta:890138,
      author       = {Maraytta, Nour},
      title        = {{S}tructure and {D}ynamics of {M}agnetocaloric {M}aterials},
      volume       = {240},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2021-00727},
      isbn         = {978-3-95806-557-4},
      series       = {Schriften des Forschungszentrums Jülich Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {vii, 146},
      year         = {2021},
      note         = {Dissertation, RWTH Aachen University, 2021},
      abstract     = {The search for more efficient use of energy has been
                      leading to a growing interest in the research field of
                      magnetocaloric materials. The magnetocaloric effect (MCE)
                      describes the change of temperature or entropy of a material
                      when exposed to a change of the magnetic field and forms the
                      basis of magnetocaloric refrigeration technologies. This
                      utilization of the effect can offer a novel method for
                      cooling that is economically feasible and ecologically
                      friendly, and hence the effect attracts the attention of
                      many researches. MCE is identified by the temperature change
                      ($\Delta$T$_{ad}$) in an adiabatic process, and by the
                      entropy change ($\Delta$S$_{iso}$) in an isothermal
                      process.Part of this thesis is devoted to the investigation
                      of the magnetocaloric effect (MCE) by direct measurements in
                      pulsed magnetic fields as well as by analyzing the
                      magnetization and specific heat data collected in static
                      magnetic fields. The emphasis is on the direct measurement
                      of the adiabatic temperature change $\Delta$T$_{ad}$ in
                      pulsed magnetic fields as it provides the opportunity to
                      examine the sample-temperature response to the magnetic
                      field on a time scale of about 10 to 100 ms, which is on the
                      order of typical operation frequencies (10 - 100 Hz) of
                      magnetocaloric cooling devices. Furthermore, the accessible
                      magnetic field range is extended to beyond 70 T and the
                      short pulse duration provides nearly adiabatic conditions
                      during the measurement. In the last years there has been an
                      upsurge in the knowledge of the MCE and many materials have
                      been investigated for their MCE characteristics. In the
                      context of this thesis, the magnetocaloric properties of the
                      single crystalline compounds MnFe$_{4}$Si$_{3}$ and
                      Mn$_{5}$Ge$_{3}$ are investigated. Moreover, the nuclear and
                      magnetic structure of the AF1' phase of the single
                      crystalline compound Mn$_{5}$Si$_{3}$ are determined. For
                      the MnFe$_{4}$Si$_{3}$, we have studied the magnetic and
                      magnetocaloric response to pulsed and static magnetic fields
                      up to 50 T. We determine the adiabatic temperature change
                      $\Delta$T$_{ad}$ directly in pulsed fields and compare to
                      the results of magnetization and specific heat measurements
                      in static magnetic fields. The high ability of cycling even
                      in high fields confirms the high structural stability of
                      MnFe$_{4}$Si$_{3}$ against field changes, an important
                      property for applications. The magnetic response to magnetic
                      fields up to $\mu_{0}$H = 35 T shows that the anisotropy can
                      be overcome by fields of approx. 7 T. For the
                      Mn$_{5}$Ge$_{3}$, we have investigated the field direction
                      dependence of the thermo-magnetic behavior in single
                      crystalline Mn$_{5}$Ge$_{3}$. The adiabatic temperature
                      change $\Delta$T$_{ad}$ in pulsed fields, the isothermal
                      entropy change $\Delta$S$_{iso}$ calculated from static
                      magnetization measurements and the heat capacity have been
                      determined for field parallel and perpendicular to the easy
                      magnetic direction [001]. The isothermal magnetization
                      measurements yield furthermore the uniaxial anisotropy
                      constants in second and fourth order, K$_{1}$ and K$_{2}$.
                      We discuss how the anisotropy affects the magneto-caloric
                      effect (MCE) and compare the results to the related [...]},
      cin          = {JCNS-2 / PGI-4 / JARA-FIT},
      cid          = {I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-4-20110106 /
                      $I:(DE-82)080009_20140620$},
      pnm          = {899 - ohne Topic (POF4-899)},
      pid          = {G:(DE-HGF)POF4-899},
      experiment   = {EXP:(DE-MLZ)HEIDI-20140101 /
                      EXP:(DE-MLZ)POLI-HEIDI-20140101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/890138},
}