2-DIMENSIONAL MAGNETIC CORRELATIONS AND MAGNETIC-ORDERING OF DY AND ER IN DYBA2CU3O7 AND ERBA2CU3O7

We have observed two-dimensional magnetic behavior associated with the magnetic ordering of Dy in DyBa2Cu3O7, and have studied the 2D magnetic correlations of Dy in DyBa2Cu3O7 as well as Er in ErBa2Cu3O7. The temperature dependence of the rod of scattering, characteristic of 2D behavior, has been measured above and below the Neel temperature (T(N) congruent-to 0.9 K for Dy, T(N) congruent-to 0.62 K for Er). For both systems the rod intensity, which is proportional to the magnetic susceptibility, is observed to increase as the temperature is decreased until T(N) is reached. Below T(N) the intensity decreases rapidly. The 2D magnetic correlation length is seen to grow continuously with decreasing temperature and then peak at the respective Neel temperatures when long range magnetic order sets in.