Static magnetic order in Bi/sub 2/Sr/sub 2/YCu/sub 2/O/sub x/ and spin freezing in Bi/sub 2/SrYCaCu/sub 2/O/sub x/ detected by muon-spin rotation

Muon-spin rotation measurements have been performed on insulating samples of Y-doped Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/. In Bi/sub 2/Sr/sub 2/YCu/sub 2/O/sub x/ muon-spin precession frequencies have been observed in zero applied field which are attributed to antiferromagnetic ordering, probably in the CuO/sub 2/ planes. The transition is broad with an ordering temperature of about 210 K. Bi/sub 2/SrYCaCu/sub 2/O/sub x/ appears to be a disordered magnetic system with a spin-freezing temperature of 15 K. These results establish that there are strong magnetic correlations in the Bi 2:2:1:2 phase which are analogous to those observed previously in La/sub 2-//sub x/Sr/sub x/CuO/sub 4/ and YBa/sub 2/Cu/sub 3/O/sub x/.