Hyperfine interactions and local environment of (57)Fe probe atoms in perovskite CaMn(7)O(12)статья
Статья опубликована в высокорейтинговом журнале
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Аннотация:Mossbauer spectroscopy has been applied for studying the local environment of (57)Fe probe atoms within iron-doped CaMn(7)O(12) manganite with a perovskite-like structure. The (57)Fe spectra recorded in the paramagnetic temperature range 90 K<T<380 K, where CaMn(7)O(12) has a rhombohedral structure (R (3) over bar), were discussed supposing Fe(3+) probe cations to replace manganese in the octahedral (Mn(3+)O(6)) and (Mn(4+)O(6)) polyhedra. A very small (<3%) part of Fe(3+) probe cations characterized by very large quadrupole splitting (similar to 2 mm/s) suggests that a few amounts of (57)Fe probe can be substituted for Mn(3+) in the (9e) positions with approximately a square planar surrounding. In the temperature range 380 K<T<450 K, the (57)Fe Mossbauer spectra undergo a sharp change which can be due to a formation (at T(CO)similar to 380 K) and a gradual growth with temperature of the cubic manganite phase (Im<(3)over bar>). At T >= 450 K, the (57)Fe spectrum reveals single Fe(3+) sites in an oxygen symmetric octahedral surrounding. This can be well explained by a fast electron exchange Mn(3+)< - >Mn(4+), leading to the crystallographic equivalence of all MnO(6) positions. At the temperature range T<T(M2) (=90 K), an appearance of the distributions of the hyperfine magnetic field values at the (57)Fe nucleus up to similar to 350 kOe (at 77.4 K) was observed. This result is an independent experimental evidence of magnetic ordering in the manganese sublattice.