Magnetization measurements and Mössbauer spectroscopy have been used to study the magnetic ordering and local structural aspects involving Gd ions in ${\mathrm{GdBa}}_2$${\mathrm{Cu}}_4$${\mathrm{O}}_8$. The reduced orthorhombicity of the 1:2:4 structure compared to the 1:2:3 is reflected by a significantly reduced asymmetry parameter η. Antiferromagnetic order of Gd moments is found at low temperatures. The magnetic ordering has a pronounced two-dimensional character. The magnetic spin configuration of the Gd moments, tilted by ∼17° with respect to the crystallographic c axis, shows the in-plane coupling between Gd ions to be due to exchange plus dipolar interactions.

• Received 18 July 1991

DOI:https://doi.org/10.1103/PhysRevB.44.12567