Metamagnetism and crystal-field splitting in pseudohexagonal CeRh3Si2

CeRh
3
Si
2
has been reported to exhibit metamagnetic transitions below 5 K, a giant crystal field splitting, and anisotropic magnetic properties from single crystal magnetization and heat capacity measurements. Here we report results of neutron and x-ray scattering studies of the magnetic structure and crystal-field excitations to further understand the magnetism of this compound. Inelastic neutron scattering and resonant inelastic x-ray scattering reveal a
J
z
=
1
/
2
ground state for Ce when considering the crystallographic
a
direction as quantization axis, thus explaining the anisotropy of the static susceptibility. Furthermore, we find a total splitting of 78 meV for the
J
=
5
/
2
multiplet. The neutron diffraction study in zero field reveals that, on cooling from the paramagnetic state, the system first orders at
T
N
1
=
4.7
K
in a longitudinal spin density wave with ordered Ce moments along the
b
axis (i.e., the [0 1 0] crystal direction) and an incommensurate propagation vector
k
=
(
0
,
0.43
,
0
). Below the lower-temperature transition
T
N
2
=
4.48
K
, the propagation vector locks to the commensurate value
k
=
(
0
,
0.5
,
0
)
, with a so-called lock-in transition. Our neutron diffraction study in applied magnetic field
H
∥
b
axis shows a change in the commensurate propagation vector and development of a ferromagnetic component at
H
=
3
kOe
, followed by a series of transitions before the fully field-induced ferromagnetic phase is reached at
H
=
7
kOe
. This explains the nature of the steps previously reported in field-dependent magnetization measurements. A very similar behavior is also observed for the
H
∥
[0 1 1] crystal direction.