H. Tou et al., AL-27-NMR AND NQR STUDIES IN THE ANTIFERROMAGNETIC HEAVY-FERMION CEPD2AL3, Journal of the Physical Society of Japan, 63(11), 1994, pp. 4176-4185
Systematic measurements of the NQR spectrum and the nuclear-spin-latti
ce relaxation rate, 1/T-1, of Al-27 in the heavy-fermion antiferromagn
etic (AF) compound CePd2Al3 have revealed that the magnetic nature dra
matically changes from showing long-range and inhomogeneous AF orderin
g for annealed and as-cast polycrystals, respectively, to a disappeara
nce of any type of magnetic ordering for single crystals. A close rela
tionship between the magnetic ordering and the structural disorder in
the Al layers isolated from the Ce-Pd layers is demonstrated. The exch
ange coupling via the Al layers along the c-axis, which leads to the A
F ground state, critically depends on the occupation and distribution
of Al atoms as proposed by Mentink et al. It is pointed out that the r
andomness remaining inevitably in the Al layers masks the intrinsic ma
gnetic excitation in the AF ordered state.