Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 30: Magnetic Materials II
MA 30.7: Vortrag
Mittwoch, 18. März 2015, 16:30–16:45, H 0112
Giant magnetic anisotropy and quantum tunneling of the magnetization in Li2(Li1−xFex)N — •Anton Jesche1 and Paul C. Canfield2 — 1Zentrum für Elektronische Korrelationen und Magnetismus, Universität Augsburg, 86135 Augsburg, Germany — 2Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
The magnetic anisotropy of 3d transition metals is usually considered to be weak. Main reason is the widely known paradigm of orbital quenching. However, a rare interplay of crystal electric field effects and spin-orbit coupling causes a large orbital contribution to the magnetic moment of iron in Li2(Li1−xFex)N. This leads not only to large magnetic moments of ∼ 5 µB per iron atom but also to an enormous magnetic anisotropy field that extrapolates to more than 200 Tesla [1]. Magnetic hysteresis emerges for T < 50 K and the coercivity fields of more than 11 Tesla exceed even the hardest 4f electron based ferromagnets.
Li2(Li1−xFex)N not only has a clear and remarkable anisotropy, generally not associated with iron moments, but also shows time-dependence more consistent with molecular magnets. In particular for low iron concentrations x ≪ 1 the spin-inversion is dominated by a macroscopic tunneling process rather than by thermal excitations.
It is shown that the huge magnetic anisotropy makes Li2(Li1−xFex)N (i) an ideal model system to study macroscopic quantum effects at elevated temperatures and (ii) a basis for novel magnetic functional materials.
[1] A. Jesche et al. Nature Commun. 5:3333 (2014)