K. Iwasa et al., LATTICE MODULATIONS INDUCED BY MAGNETOELASTIC EFFECT IN CRYSTALS CONTAINING RARE-EARTH ELEMENTS, Journal of the Physical Society of Japan, 63(1), 1994, pp. 127-134
Lattice modulations associated with magnetic order in Tm and Er were i
nvestigated by means of X-ray diffraction. Satellite peaks at wave vec
tors (0 0 2q(0)) and (0 0 4q(0)) were observed in Tm where q(0) is the
fundamental wave number specifying the modulations of the magnetic mo
ment along the hexagonal c-axis. The modulation amplitude, the atomic
displacement along the c-axis, was estimated to be of the order of 10(
-3) Angstrom. No peak was detected at q(0). Peaks for 2q(0) and 4q(0)
were observed also in Er. The amplitude of the 2q(0) modulations decre
ased with decreasing temperature below 30 K. A model based on the magn
etoelastic interactions was constructed to calculate these amplitudes
of lattice modulations. It involves the elastic, exchange and crystal
field energies. The latter two magnetic energies were assumed to vary
with the interatomic distance. This model, combined with the temperatu
re variations of the magnetic moment, was found to reproduce the tempe
rature dependence of the lattice modulations in Tm and Er. X-ray diffr
action measurements were also made for UPdIn and NdCo2Si2. The magneto
elastic effects in these materials appear to be much weaker than those
in Tm and Er.