MAGNETIC ORDER OF CU IN ND2-XCEXCUO4

The magnetic ordering in single crystals of Nd2-xCexCuO4 with x = 0.0 to 0.22 has been studied by neutron diffraction measurements. Long-range antiferromagnetic order for Cu is observed for crystals with small Ce concentrations. Both the ordered moment for Cu and the Neel temperature decrease with increasing Ce concentration x. Two Cu spin reorientation transitions are also observed for crystals with small Ce concentrations. The temperature dependence of the (1/2 1/2 0) magnetic Bragg peak shows that these spin reorientation transitions are sharp for the pure sample, while they are not as sharp for the doped samples due to the randomness of the Ce. The fraction of the Cu spins which participate in the spin reorientations also decreases with increasing x. In Nd2CuO4, both spin reorientation transition temperatures increase with magnetic field at the rate of about 1.2 and 0.8 K/T, respectively.