Chapter 8
Mössbauer Spectroscopy in External
Magnetic Fields
Michael Reissner
Abstract The application of external magnetic fields allows to broaden the knowledge, which can be gained by Mössbauer spectroscopy enormously. In combination
with magnetic measurements, detailed information about local magnetic and electronic structure can be obtained. After an introduction to the influence of an external
magnetic field on hyperfine interactions, examples are given. Starting from simple
magnetic structures like para-, ferro-, and antiferro-magnetic ones, investigations on
complex magnetic structures with spin canting are discussed. Also results on materials with inhomogeneous magnetic structures like spin glasses will be presented.
Special focus will be on the influence of high external fields on the spin dynamics.
8.1 Introduction
In contrast to magnetization measurements or NMR investigations the application of
an external field is not a prerequisite to get information about the magnetic behaviour
of a compound in case of Mössbauer spectroscopy. Nevertheless measurements in
external magnetic fields have been performed since the very early days of Mössbauer spectroscopy, because a lot of new and more in-depth information can be
gained. Especially in the case of the investigation of magnetic ground state properties in-field measurements are extremely valuable. The determination of the precise
hyperfine structure in magnetically ordered samples is often a non-trivial task. The
simultaneous presence of magnetic dipole and electric quadrupole interaction makes
modelling of the hyperfine structure quite complicate. But if external field is high
the influence of electric field gradient can be reduced and interpretation of measured
spectra might become easier. One of the first applications of external fields in Mössbauer spectroscopy was the measurements of the sign of the hyperfine field in α-Fe
[1, 2]. For alloys with traces of iron the local susceptibility of the iron moments
could be determined [3–7]. Knowledge about crystal field parameters and the atomic
arrangement in complex structures, as well as the investigation of magnetic order can
M. Reissner (B)
Institute of Solid State Physics, TU Wien, Vienna, Austria
e-mail: reissner@tuwien.ac.at
© Springer Nature Singapore Pte Ltd. 2021
Y. Yoshida and G. Langouche (eds.), Modern Mössbauer Spectroscopy,
Topics in Applied Physics 137, https://doi.org/10.1007/978-981-15-9422-9_8
381
Mössbauer Spectroscopy in External
Magnetic Fields
Michael Reissner
Abstract The application of external magnetic fields allows to broaden the knowledge, which can be gained by Mössbauer spectroscopy enormously. In combination
with magnetic measurements, detailed information about local magnetic and electronic structure can be obtained. After an introduction to the influence of an external
magnetic field on hyperfine interactions, examples are given. Starting from simple
magnetic structures like para-, ferro-, and antiferro-magnetic ones, investigations on
complex magnetic structures with spin canting are discussed. Also results on materials with inhomogeneous magnetic structures like spin glasses will be presented.
Special focus will be on the influence of high external fields on the spin dynamics.
8.1 Introduction
In contrast to magnetization measurements or NMR investigations the application of
an external field is not a prerequisite to get information about the magnetic behaviour
of a compound in case of Mössbauer spectroscopy. Nevertheless measurements in
external magnetic fields have been performed since the very early days of Mössbauer spectroscopy, because a lot of new and more in-depth information can be
gained. Especially in the case of the investigation of magnetic ground state properties in-field measurements are extremely valuable. The determination of the precise
hyperfine structure in magnetically ordered samples is often a non-trivial task. The
simultaneous presence of magnetic dipole and electric quadrupole interaction makes
modelling of the hyperfine structure quite complicate. But if external field is high
the influence of electric field gradient can be reduced and interpretation of measured
spectra might become easier. One of the first applications of external fields in Mössbauer spectroscopy was the measurements of the sign of the hyperfine field in α-Fe
[1, 2]. For alloys with traces of iron the local susceptibility of the iron moments
could be determined [3–7]. Knowledge about crystal field parameters and the atomic
arrangement in complex structures, as well as the investigation of magnetic order can
M. Reissner (B)
Institute of Solid State Physics, TU Wien, Vienna, Austria
e-mail: reissner@tuwien.ac.at
© Springer Nature Singapore Pte Ltd. 2021
Y. Yoshida and G. Langouche (eds.), Modern Mössbauer Spectroscopy,
Topics in Applied Physics 137, https://doi.org/10.1007/978-981-15-9422-9_8
381