Freezing of anisotropic spin clusters

A spin-glass compound, (Formula presented) shows quasi-three-dimensional magnetic ordering below (Formula presented) A remarkable feature is that the magnetic correlation length along the orthorhombic (Formula presented) axis is much longer than that along the (Formula presented) axis, suggesting that the spin structure is closely related to the diagonal stripe structure. The spin-glass state can be expressed as a random freezing of quasi-three-dimensional spin clusters with anisotropic spin correlations (Formula presented) and (Formula presented) at 1.6 K). The new magnetic state is important as an intermediate phase between the three-dimensional antiferromagnetic ordered phase in (Formula presented) and the incommensurate phase in (Formula presented) in which the positions of the incommensurate peaks are rotated by (Formula presented) in reciprocal space about (Formula presented) from those observed in the superconducting (Formula presented) compounds.