Berlin 2018 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 21: Poster I
MA 21.111: Poster
Dienstag, 13. März 2018, 09:30–13:00, Poster A
Giant magnetic hyperfine field, spin dynamics and colossal transverse field sensitivity in the single-atomic magnet Li2(Li1−xFex)N with x≪1 — •Sascha Albert Bräuninger1, Sirko Kamusella1, Rajib Sarkar1, Manuel Fix2, Stephan Jantz2, Anton Jesche2, Andre Zvyagin3, and Hans-Henning Klauss1 — 1Institute 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 57Fe Mössbauer studies on large single crystals of diluted Fe ions in Li2(Li1−xFex)N which forms a hexagonal symmetric α-Li3N crystal matrix. The homogeneity of the nanoscale distributed isolated Fe centers is shown. The isolated Fe centers, e.g. for x=2.5(1)%, exhibit a giant magnetic hyperfine field of B=70.22(1) T parallel to the largest principle axis Vzz=−154.10(19) V/Å2 of the electric field gradient at 2 K, same for other x≪1. The magnetic hyperfine field fluctuates between 50 K and 300 K probed by Mössbauer spectroscopy described by a two-level relaxation model. The spin dynamics is similar to a behavior known from single-molecule magnets. An Arrhenius frequency plot ν=ν0e−EA/kBT yields a thermal activation barrier of EA=542(8) K and ν0=216(22) GHz which consistent with magnetization investigations. An applied transverse magnetic field study up to 5 T at 70 K shows a sensitivity two orders of magnitude higher than expected from the conventional theory of nanomagnets.