Magnetic ordering in single crystals of PrBa2Cu3O7-δ

Heat capacity measurements on pure but twinned single crystals of PrBa 2 Cu 3 O 7-δ reveal a sharp peak at T N Pr = 16.6 K , which according to thermal expansion, neutron diffraction, and magnetic susceptibility measurements originates from an antiferromagnetic ordering of the Pr-ion moments. A modest coupling to the Cu(2) spin system is observed. Below T N Pr a first-order transition in the magnetic structure of the Pr spin system (at 13.4 K in warming; 11 K in cooling) is found. Field-dependent heat capacity data show anisotropic temperature dependences of the c p -peaks and recover a Schottky-like anomaly due to the crystal-field-split ground state of the Pr3 + .