Despite the high prominence of the perovskites BiFeO(3) and KNbO(3) the solid solution between the two has received little attention. We report a detailed neutron and synchrotron X-ray powder diffraction, and Raman spectroscopy study which demonstrates an R3c→P4mm→Amm2 series of structural phase transitions similar to that exhibited by the PbZrO(3)-PbTiO(3) solid solution.

aWe report a systematic X-ray and powder neutron diffraction study of the geometrically frustrated

CaMnO exhibits a complex layered structure comprised of MnO layers separated by Ca ions. In contrast with the more traditional triangular delafossite layered materials the MnO layers additionally exhibit an ordered vacancy, which forms a 'bow-tie' like arrangement of the Mn ions. We report a comprehensive study of the magnetic properties of a series of CaMnO materials with different morphologies. EXAFS and XANES analysis confirm no differences in either manganese environment or oxidation state between materials. Apparent differences in magnetic order from SQUID magnetometry can be rationalised by uncompensated surface spins arising as a result of changes to the surface to volume ratio between morphologies. Furthermore, these data suggest these materials are potentially frustrated in nature, due to the triangular connectivity of Mn spins, with a simple 'spin-up/spin-down' (↑↓) antiferromagnetic model unable to explain the data collected.

No abstract

We report the synthesis and comprehensive AC and DC susceptibility measurements of KxRu4-yNiyO8 hollandite. The value of the relative frequency shift, δTf, has been determined as 0.025 which is within the range expected for spin-glass systems (0.005 -0.06). Additionally, the characteristic flipping time of a single spin flip, τ0, and the dynamical critical exponent, -zv were determined to have values 5.82 x 10 -8 s and 6.1(3) respectively from the Power Law. Whilst the value of τ0 is comparatively very large, -zv is consistent with what is expected for spin glass systems. Field cooled hysteresis behaviour demonstrates a small increase in the remnant magnetisation (at 2 K) on increasing the strength of the cooling field suggesting that the degree of short-range correlations increases consistent with the formation of larger spin clusters. Thermoremnant magnetisation data indicates an exponential-like decay of the magnetisation as a function of time with the remnant magnetisation remaining nonzero. However, it is clear from these data that multiple components contribute to the decay behaviour. Collectively, these data confirm spin-glass character for K0.73(3)Ni1.9(5)Ru2.1(5)O8 and clearly demonstrate that the magnetic behaviour of this material is far from simplistic.