Magnetic Structure of HoCo sub 5 Below Room Temperature

Previous neutron diffraction studies have established the ferrimagnetic coupling of Co and Ho magnetic moments in HoCo sub 5 . However, owing to the competition of Co and Ho local anisotropies, which have opposite signs, a noncollinear magnetic structure is suggested at low temp. By combining magnetization measurements on a single crystal with Mossbauer and neutron diffraction experiments, the directions of the Co and Ho magnetizations were compared with those of the bulk spontaneous magnetization. Above 200K all the magnetic moments are parallel to the c axis of the hexagonal structure. Below 200K the magnetic structure becomes noncollinear owing to the reorientation of the magnetizations. The direction of the bulk spontaneous magnetization is very different from those of the Co and Ho magnetizations.--AA