Specific heat and magnetic order in GdBa2-xSrxCu3O7

C. H. Watson, Louisiana State University
D. A. Browne, Louisiana State University
Jing Chun Xu, Louisiana State University
R. G. Goodrich, Louisiana State University


We report measurements of the specific heat of GdBa2-xSrxCu3O7 for x=0, 0.25, and 0.5 in the temperature range 0.65 K. In addition, measurements in magnetic fields from 0 to 3 T for the x=0 sample are reported. In each case a peak in the specific heat at the antiferromagnetic ordering temperature is recorded and analyzed. Strontium doping does not change the Néel temperature, but drastically changes the shape of the specific-heat curve below the ordering temperature. The Néel temperature is reduced proportional to the square of the applied magnetic field. A model calculation of the spin-wave contribution to the low-temperature specific heat shows that strong couplings along the c axis and weak couplings in the a-b plane are responsible for the antiferromagnetic order. © 1989 The American Physical Society.