Magnetization measurements of antiferromagnetic domains in Sr2Cu3O4Cl2 - art. no. 134433

The Cu3O4 layer in Sr2Cu3O4Cl2 is a variant of the square CuO2 lattice of t he high-temperature superconductors, in which the center of every second pl aquette contains an extra Cu2+ ion. Whereas the ordering of the spins in th e ground-state and the spin-wave excitations of this frustrated spin system are both well understood, we find peculiar behavior resulting from antifer romagnetic domain walls. Pseudodipolar coupling between the two sets of Cu2 + ions results in a ferromagnetic moment, the direction of which reflects t he direction of the antiferromagnetic staggered moment, allowing us to prob e the antiferromagnetic domain structure. After an excursion to the high fi elds (>1 T), as the held is lowered, we observe the growth of domains with ferromagnetic moment perpendicular to the field. This gives rise to a finit e domain wall susceptibility at small fields, which diverges near 100 K, in dicating a phase transition. We also find that the shape of the sample infl uences the domain-wall behavior.