Helifan: A new type of magnetic structure

The magnetic phases which have earlier been observed when a magnetic field is applied in the plane of the helical magnetic structure of Ho are identified with structures, intermediate between the helix and the fan, which we call helifans. A number of helifan structures have been calculated by a self-consistent mean-field method, and one of them accounts very well for the observed neutron-diffraction pattern. Different sequences of helifans may, in principle, be produced by varying the magnetic field and temperature, and modifying the exchange by alloying.