Low temperature magnetic ordering of Ba2Cu3O4Cl2 with Cu3O4 planes

Magnetic properties of single crystal Ba2Cu3O4Cl2 with Cu3O4 planes were investigated by temperature- and magnetic-field-dependent anisotropic magnetization M(T, H) and zero-field-μSR. Muon spin precession was observed below as well as above T = 32 K where an anomaly in M(T) appears. At this temperature the frequency of the precession changes and the damping of it diverges. This is an evidence for a magnetic transition. We also found the temperature dependence of the H-linear component of M(H) shows a maximum around T = 80 K, which is similar to the behavior of low-dimensional magnets with an antiferromagnetic interaction.