Four new oxyselenides with nominal formula Sr(2)AO(2)M(2)Se(2) (A=Co, Mn; M=Cu, Ag) have been synthesized. They all crystallize in an I4/mmm space group and consist of alternating perovskite-like (Sr(2)AO(2))(2+) blocks and antiflourie (M(2)Se(2))(2-) layers, which are relatively rare layered oxyselenides reported so far that are isostructural to Sr(2)Mn(3)Sb(2)O(2). From powder X-ray diffraction data, compounds Sr(2)CoO(2)Cu(2)Se(2) and Sr(2)CoO(2)Ag(2)Se(2) are found near stoichiometric, whereas Sr(2)MnO(2)Cu(2-δ)Se(2) and Sr(2)MnO(2)Ag(2-δ)Se(2) possess substantial copper or silver vacancies (δ≈0.5), consistent with their oxysulfide analogues. X-ray photoelectron spectroscopy measurements indicate the readily oxidization of Mn(2+) ions should be responsible for the occurrence of Cu/Ag vacancies. The rigid (Sr(2)AO(2))(2+) blocks within these compounds constrain the basal lattice parameters in the ab plane and result in largely deformed tetrahedral sites for the large silver ions. Magnetic susceptibility measurements of Sr(2)CoO(2)M(2)Se(2) (M=Cu, Ag) show complex antiferromagnetic transitions, while Sr(2)MnO(2)M(2-δ)Se(2) (M=Cu, Ag) show high-temperature Curie-Weiss behavior, followed by low-temperature antiferromagnetic transitions at 54 K and 67 K, respectively. Except for Sr(2)MnO(2)Ag(2-δ)Se(2), the other three compounds exhibit p-type semiconducting transport properties, with the measured resistivities several orders lower than their oxysulfide analogues. Hall measurement reveals high mobilities of Sr(2)CoO(2)M(2)Se(2) (M=Cu, Ag) compounds at room temperature. The unusually small optical band gaps (~0.07 eV) of Sr(2)CoO(2)Cu(2)Se(2), Sr(2)CoO(2)Ag(2)Se(2), and Sr(2)MnO(2)Cu(2-δ)Se(2) are also reported.

We study the change in magnetisation with paramagnetic Al addition in the CoFeNi 0.5 cr 0.5-Al x (x: 0, 0.5, 1, and 1.5) complex concentrated alloy. The compositions were developed utilising the Mulliken electronegativity and d-electron/atom ratio. Spherical FeCr rich nanoprecipitates are observed for X: 1.0 and 1.5 in an AlCoNi-rich matrix. A ~ 5 × increase in magnetisation (from 22 to 96 Am 2 /kg) coincides with this nanoprecipitate formation-the main magnetic contribution is determined to be from FeCr nanoprecipitates. The magnetisation increase is strange as paramagnetic Al addition dilutes the ferromagnetic Fe/Co/Ni additions. In this paper we discuss the magnetic and structural characterisation of the cofeni 0.5 cr 0.5-Al x composition and attempt to relate it to the interfacial energy. The innovation of new materials has been deemed to be the key topic for development of new technologies in our modern world. For alloys, the traditional approach has been to consider the effect of multiple dilute additions to a larger alloy matrix. New complex concentrated alloys (CCAs), which are near-equimolar multiple element alloys (> 3) challenge this view and have pushed alloy research towards the centre of phase diagrams 1,2. Multiple alloying components mean that they can possess large property permutations owing to the vast compositional space that they cover. Considerable work has been done on understanding how compositionalstructure affects mechanical properties. However, their functional properties are rarely the primary focus. As the base elements of CCAs are often CoFeNi (which is a known soft magnetic alloy), this can provide a basis for alloy design 1-5. Our motivation in this work is to therefore investigate the potential of CCAs as soft magnetic materials.

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