American Physical Society, Physical review B, 14(83), 2011
DOI: 10.1103/physrevb.83.144419
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Several doped 6H hexagonal ruthenates, having the general formula Ba 3 MRu 2 O 9 , have been studied over a significant period of time to understand the unusual magnetism of ruthenium metal. However, among them, the M=Fe compound appears different since it is observed that unlike others, the 3d Fe ions and 4d Ru ions can easily exchange their crystallographic positions, and as a result many possible magnetic interactions become realizable. The present study involving several experimental methods on this compound establishes that the magnetic structure of Ba 3 FeRu 2 O 9 is indeed very different from all other 6H ruthenates. Local structural study reveals that the possible Fe/Ru site disorder further extends to create local chemical inhomogeneity, affecting the high-temperature magnetism of this material. There is a gradual decrease of 57 Fe Mossbauer spectral intensity with decreasing temperature (below 100 K), which reveals that there is a large spread in the magnetic ordering temperatures, corresponding to many spatially inhomogeneous regions. However, finally at about 25 K, the whole compound is found to take up a global glasslike magnetic ordering.