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.