Diffraction experiments on GdCu₂in using hot neutrons

Gd compounds with nonmagnetic partner elements are attractive probes for evaluating magnetic exchange interactions. In the Gd³⁺ ion the f-electrons have zero angular momentum with a spherical charge density. Therefore the crystal-field interaction is negligible. Compounds with one Gd atom per primitive unit cell deserve special interest because their magnetic anisotropy can be calculated from first principles provided the classical dipole-dipole interaction dominates. We investigated the magnetic structure of the Heusler compound GdCu₂In by neutron diffraction and find a complex antiferromagnetic order. Using numerical methods it is possible to interpret the data within the dipolar model. A spin reorientation occurring just below the Néel temperature is inferred.