Dresden 2020 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Bio- and Molecular Magnetism (joint session MA/CPP)

CPP 25.2: Vortrag

Montag, 16. März 2020, 15:15–15:30, HSZ 101

Magnetic field tuning of low energy spin dynamics in the single-atomic magnet Li2(Li1−xFex)N with x≪1 — •Sascha Albert Bräuninger1, Sirko Kamusella1, Felix Seewald1, Rajib Sarkar1, Manuel Fix2, Stephan Jantz2, Anton Jesche2, Andre Zvyagin3, and Hans-Henning Klauss11Institute of Solid State and Materials Physics, TU Dresden, D-01069 Dresden, Germany — 2Institute of Physics, University Augsburg, D-86135 Augsburg, Germany — 3Max-Planck-Institute for the Physics of Complex Systems, Nöthnitzer Str., 38, D-01187 Dresden, Germany

We present a systematic 57Fe-Mössbauer study on highly diluted Fe centers in Li2(Li1−xFex)N single-crystals as a function of temperature and magnetic field applied transverse and longitudinal with respect to the single-ion anisotropy axis. Below 30 K the Fe centers exhibit a giant magnetic hyperfine field of BA=70.25(2) T parallel to the axis of strongest electric field gradient Vzz=−154.0(1) V/Å2. Fluctuations of the magnetic hyperfine field are observed between 50 K and 300 K and described by the Blume two-level relaxation model. An Arrhenius analysis yields a single thermal activation barrier of ĒA=570(6) K. Mössbauer spectroscopy studies with applied transverse magnetic fields up to 5 T reveal a large increase of the fluctuation rate by more than one order of magnitude. The experimental observations are qualitatively reproduced by a single-ion effective spin Hamiltonian analysis assuming a Fe1+ d7 charge state with unquenched orbital moment and a J=7/2 ground state.

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