Neutron-diffraction study of the magnetic structure of GdB2C2

There are two purposes in this study. One is to see the performance of our powder neutron diffractometer, HERMES, for a very heavy neutron absorber, GdB2C2. The other is to see the magnetic structure of GdB2C2 as a compound of the tetragonal RB2C2 family, in which antiferroquadrupolar and magnetic interactions compete. We choose GdB2C2 to clarify the purely magnetic interaction in this system because the Gd ion has no quadrupolar moment. We obtained diffraction data using reflection geometry and concluded that the magnetic interaction is antiferromagnetic in the c plane and ferromagnetic along the c axis. (orig.)