MAGNETIC-FIELD DEPENDENCE OF LOW-TEMPERATURE HEAT-CAPACITIES OF GDBA2CU4O8

Calorimetric measurements were made on a coprecipitation-synthesized G dB2Cu4O8 at temperatures between 0.5 and 13 K and in magnetic fields u p to 7 T. The heat capacity data in zero field show an antiferromagnet ic transition with T-N similar or equal to 2.2 K followed by a broad s houlder below, which is identified from entropy consideration to be al so associated with the Gd3+-ordering. Similar observations were made i n a magnetic field of 2 T, except that T-N was lowered to 1.6 K. At a higher field of 4 T the calorimetric signature of a long range orderin g disappeared, leaving behind a Schottky-type anomaly with a peak near 1 K. This peak moved to 2.5 K at 7 T.