Neutron scattering study of the field-dependent ground state and the spin dynamics in spin-one-half NH4CuCl3.
Elastic and inelastic neutron scattering experiments have been performed on the dimer spin system NH4CuCl3, which shows plateaus in the magnetization curve at m=1/4 and m=3/4 of the saturation value. Two structural phase transitions at T1 approximately 156 K and at T(2)=70 K lead to a doubling of the crystallographic unit cell along the b direction and as a consequence a segregation into different dimer subsystems. Long-range magnetic ordering is reported below T(N)=1.3 K. The magnetic field dependence of the excitation spectrum identifies successive quantum phase transitions of the dimer subsystems as the driving mechanism for the unconventional magnetization process in agreement with a recent theoretical model.
Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. christian.rueegg@psi.ch
Ch
Ch
Rüegg
M
M
Oettli
J
J
Schefer
O
O
Zaharko
A
A
Furrer
H
H
Tanaka
K W
KW
Krämer
H-U
HU
Güdel
P
P
Vorderwisch
K
K
Habicht
T
T
Polinski
M
M
Meissner