Calorimetric evidence of antiferromagnetism in GdBa2Cu3O6+δ

Abstract Heat capacity measurements between 1.8 and 10K have been made on the superconductor GdBa 2 Cu 3 O 6+δ with δ ⋍ 0.7 and T c ⋍ 94K. A well defined magnetic transition prevails at 2.22K. The entropy involved agrees well with the complete antiferromagnetic ordering of Gd 3+ ions.