Successive Short- and Long-Range Magnetic Ordering in BaMn(SeO) with Honeycomb Layers of Mn Ions Alternating with Triangular Layers of Mn Ions.

Mixed-valent BaMnMn(SeO) crystallizes in a monoclinic structure and has honeycomb layers of Mn ions alternating with triangular layers of Mn ions. We established the key parameters governing its magnetic structure by magnetization and specific heat measurements. The title compound exhibits a close succession of a short-range correlation order at = 10.

Highly anisotropic 1/3-magnetization plateau in a ferrimagnet CsCu(SeO)·2HO: topology of magnetic bonding necessary for magnetization plateau.

We prepared CsCu(SeO)·2HO composed of Cu ions at square-planar coordination sites and characterized its structural and magnetic properties, to show that CsCu(SeO)·2HO is a ferrimagnet exhibiting a highly anisotropic 1/3-magnetization plateau. This unprecedented anisotropy in a magnetization plateau is the consequence of three effects, namely, the orthogonal arrangements of the corner-sharing CuO square planes, the nearest-neighbour antiferromagnetic exchange, and the anisotropic -factor of the Cu ions at square-planar coordination sites. By analyzing the topology of magnetic bonding, we found why magnetic plateaus are observed only for certain ferrimagnets and antiferromagnets.

Quasi-1D XY antiferromagnet SrNi(SeO)Cl at Sakai-Takahashi phase diagram.

Uniform quasi-one-dimensional integer spin compounds are of interest as a potential realization of the Haldane conjecture of a gapped spin liquid. This phase, however, has to compete with magnetic anisotropy and long-range ordered phases, the implementation of which depends on the ratio of interchain J' and intrachain J exchange interactions and both uniaxial D and rhombic E single-ion anisotropies. Strontium nickel selenite chloride, SrNi(SeO)Cl, is a spin-1 chain system which passes through a correlations regime at T ~ 12 K to long-range order at T = 6 K.