Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Correlated Electrons: Poster Session
TT 45.88: Poster
Donnerstag, 29. März 2012, 15:00–19:00, Poster B
Magnetic structures and magnon dispersion of LaSrFeO4 — •N. Qureshi1, H. Ulbrich1, Y. Sidis2, A. Cousson2, and M. Braden1 — 1University of Cologne — 2LLB, Saclay (France)
We have conducted an extensive study on the single-layered perovskite LaSrFeO4, a transition metal oxide of the Ruddelsden-Poppers series. This system orders antiferromagnetically at TN=380 K and undergoes two further magnetic phase transitions at 90 K and 30 K [1,2] whose nature is still unclear. Our neutron diffraction experiments shed some light on this open issue: We have observed that there is no significant difference between the three magnetic structures. Although, the presence of four magnetic domains renders it impossible to determine the Fe moment direction within the basal plane using unpolarized neutrons. Hence, we conclude that the transitions must be connected to a spin reorientation within the basal plane. Additionally, we have investigated the magnon dispersion along two main symmetry directions. We find that the dispersions are well described by a Heisenberg antiferromagnet Hamiltonian including isotropic nearest and next-nearest neighbour interaction as well as an effective magnetic anisotropy field. The resulting values fit well into the series of the isostructural homologues. In LaSrFeO4 the Fe ions nominally present a three-valent 3d5 state yielding S=2.5 and L=0. However, the results of our neutron study give rise to the assumption of a non-quenched orbital moment.
References
J. L. Soubeyroux et al., J. Solid State Chem. 31, 313 (1980).
M. H. Jung et al., J. Appl. Phys. 97, 10A926 (2005)