OBSERVATION OF A COMMENSURATE TEMPERATURE PLATEAU INDUCED BY C-AXIS APPLIED MAGNETIC-FIELDS IN HOLMIUM

Measurements of the magnetic structure of holmium in c-axis applied magnetic fields were made by neutron diffraction in the (h0l) plane. In applied fields of 1.7 and 2.2 T directed along the c-axis, the overall periodicity of the spiral structure locks into the commensurate superlattice value 4c 0 over a finite range of temperature (approximately 2 K at 2.2 T) near 98 K, whereas no such effect is seen in the crystal in zero field. The commensurate plateau extends between two transitions bracketing 98 K reported in magnetization and dilatometry by Steinitz et al. [Phys. Rev. B 40, 763 (1989)]. No new satellites were found in this temperature range, but the intensities of the fundamental magnetic Bragg peaks exhibited precursor behavior as the commensurate state was approached in temperature both from above and below.