Chiral-like critical behavior in the antiferromagnet cobalt glycerolate.

Critical exponents closely matching those of the N=2 chiral universality class have been obtained for the layered magnetic system cobalt glycerolate using muon spin relaxation. This class was originally introduced to represent geometrically frustrated triangular stacked-layer XY magnets with chiral noncollinear spin structures. Since the present magnetic system is a canted XY system without geometrical frustration or chiral degeneracy, the results indicate that the order parameter for canting in this system plays a similar role to the chiral order parameter in the geometrically frustrated systems, strongly suggesting that both types of noncollinear system share the same universality class.

Layered cobalt hydroxysulfates with both rigid and flexible organic pillars: synthesis, structure, porosity, and cooperative magnetism.

The synthesis and characterization of two members of a family of porous magnetic materials is described. The structures of Co4(SO4)(OH)6(C2N2H8)0.5*3H2O and Co4(SO4)(OH)6(C6N2H12)0.5*H2O and their thermal stability can be tailored via the choice of organic pillar. The interactions between the pillaring agent and the compositionally complex inorganic layer are discussed. The influences of two pillaring agents i.e., the flexible ethylenediamine and the relatively rigid 1,4-diazabicyclo[2,2,2]octane, on thermal stability, rigidity upon guest loss, and magnetic behavior of the pillared solids are compared. The magnetism of the pillared layered cobalt hydroxides is complex due to the influences of multiple metal sites, inter- and intralayer exchange, spin-orbit coupling, and geometrical frustration. The wide variety of potential pillars, oxyanions, and possible metal substitutions at the octahedral and tetrahedral sites offers the possibility of tailoring the magnetic and porous properties of these materials.

MEM(TCNQ)2 at room temperature and 10 K, and the absence of a spin-Peierls transition.

Precise X-ray determinations of the crystal structure of the 1:2 complex of N-ethyl-N-methylmorpholinium and 7,7,8,8-tetracyano-p-quinodimethanide, abbreviated as MEM-TCNQ or MEM(TCNQ)(2) (C(7)H(16)NO(+).2C(12)H(4)N(4)(0.5-)), have been performed at 293 and at 10 K. Evidence for the expected spin-Peierls transition at 19 K is not found, and this may follow from radiation damage to the crystal or from insufficient equipment sensitivity.