Three-dimensional magnetic ordering in Bi/sub 2/CuO/sub 4/

The heat capacity of Bi/sub 2/CuO/sub 4/ has been measured from 5 to 350 K in an adiabatic calorimeter. A long range ordering peak was found at 42.7 K due to the establishment of three-dimensional antiferromagnetic order. The magnetic entropy calculated for the anomaly corresponds to the theoretical value for spin 1/2, /spl Delta/S=Rln2, discarding the existence of any lower dimensional magnetic contribution at a higher temperature.