μSR study of frustrated S=12 Delafossites YCuO2+δ

Over-oxidized Delafossites MCuO2+δ are frustrated antiferromagnets formed by a stacking of alternating M3+ and Cu(1+2δ)+ planes. Frustration arises from the geometry of the magnetic lattice, which is based on corner sharing triangles. We present here a study of YCuO2.5 and YCuO2.66, both with S=12 spin magnetic atoms. μSR data of YCuO2.5, a one-dimensional Δ-chain compound, show dynamical behaviour with no transition to a frozen state down to 100 mK. YCuO2.66, which possesses a 2D kagomé-like magnetic lattice, orders at 100 K, with an internal magnetic field of about 700 G at 5 K. Further hole doping is achievable in this compound through Ca2+/Y3+ substitution. We show that only 1% Ca doping strongly reduces the transition temperature to 80 K.