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Inhomogeneous magnetic state in LaMn0.5Fe0.5O3

Dmitry Karpinsky 1Igor Troyanchuk Henryk Szymczak 2

1. Institute of Solid State and Semiconductor Physics National Academy of Sciences (ISSSP), P. Brovki, 17, Minsk 220072, Belarus
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland


Magnetization and neutron diffraction studies on LaMn0.5Fe0.5O3+d perovskites have been performed. In order to exclude the influence of Mn4+ ions from concideration the as-prepared one has been annealed in vacuumed tube that led to nearly stoichiometry of the sample that has been confirmed by computer refinement of the NPD data. The oxygen reduction led to certain changes in the magnetic properties of the sample.
Both of the samples have smeared magnetic transition and branching point near the same temperature (~ 180 K) thus demonstrating inhomogeneous magnetic states of the compounds. Although the reduced sample has a less pronounced divergence between FC and ZFC curves, possibly confirming a stronger ferromagnetic component in comparison with the as-prepared one. The reduced sample most likely has certain ferromagnetic order which is seen from the neutron measurements, whereas the as-prepared compound demonstrates dominated spin glass component. The NPD measurements revealed an antiferromagnet component in the both samples. Most likely an origin of the antiferromagnet ordering is similar to that discussed for LaCo0.5Fe0.5O3 compound thus confirming a certain phase separation. An essential role of competed phases is supported by the field magnetization measurements, thus even in relatively high magnetic fields no saturation was observed.
Fitting of the NPD data revealed that differences in the Mn-O distances are almost neglected thus indicates a removing of the static Jahn-Teller distortions. Magnetic properties of the stoichiometric solid solution can be well described in the terms of superexchange model assuming positive Mn3+ - O - Mn3+ dynamic interactions whereas Fe3+ - O - Fe3+ interactions are strongly antiferromagnetic.


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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium K, by Dmitry Karpinsky
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 11:50
Revised:   2009-06-07 00:44