Studies of the magnetic behaviour of ErAl3(BO3)4 and the effects of the crystal field

Single crystals of ErAl3(BO3)(4) were produced by flux growing techniques. The principal magnetic susceptibility, XI, perpendicular to the symmetry axis of the crystal was measured in the range 300-14.2 K, and the principal anisotropy (X parallel to -X perpendicular to) was determined from 300 to 77 K, which turned out to be negative throughout. A crystal field conforming to D-3 site symmetry (obtained from structural data) accounts very well for the observed thermal variation of the magnetic susceptibilities; this yields g factors, g parallel to and g perpendicular to, of 2.32 and 8.95, respectively. The electronic heat capacity is computed, and shows a Schottky anomaly at around 45 K. Calculated quadrupole splitting of Er-167 due to crystal field effects shows a smooth decrease with decreasing temperature. The hyperfine heat capacity, contributed mainly by magnetic hyperfine splitting, displays a rounded maximum at about 8 mK. (C) 1998 Elsevier Science Ltd. All rights reserved.