Antiferromagnetic order above antiferroquadrupolar transition temperature of HoB2C2

Abstract We have performed neutron diffraction measurements on a single crystal sample of tetragonal Ho 11 B 2 C 2 , which shows an antiferromagnetic order above an antiferroquadrupolar transition temperature. The magnetic structure of the intermediate phase, phase IV, has a long periodicity, and the order is short ranged. It is represented with a propagation vector k=[1+δ δ δ′] , where δ ∼0.11 and δ ′∼0.04.