STUDIES OF THE MAGNETIC PHASE-DIAGRAM OF HOLMIUM USING NEUTRON-DIFFRACTION

We report measurements of the intensity and position of the satellites arising from the helimagnetic structure of holmium in magnetic fields applied along different crystal axes, concentrating on lock-in effect s at commensurate values of the spiral wave vector tau. We have made t he first observations of the lock-in at tau = 1/5 near 42 K in a 3 T c -axis field as well as the lock-in at tau = 1/4 in a 3 T b-axis field. We have also observed a lock-in at tau = 5/18 in a b-axis field near the Neel temperature of 132 K, in contrast to an earlier reported valu e of 8/29. This illustrates the origin of the splitting previously rep orted by us in magnetization and dilatometric measurements.