Magnetic structure of erbium in field

The magnetic structure of erbium in a field up to 2.8 T along the c-axis has been studied by eleastic neutron scattering. At low temperatures the conical structure with q = 5/21 persist field. The sequence of ionics-in antiferromagnetic phases at higher temperatures in zero field is destroyed by the field. Larger fields stabilize the conical phase, though at temperatures above 20 K there is no longer a lock-in at q = 5/21. For fields between 2.1 and 2.8 T we observe a new conical phase with a lock-in at q = 1/4. This phase is stable between 34 and 39 K.