Understanding the magnetism of CeRh3Si2 through neutron and x-ray scattering

CeRh3Si2 has been reported to exhibit two magnetic transitions below 5 K and multiple steps in magnetization isotherms (called metamagnetic transitions) at 1.7 K, a giant crystal field splitting, and anisotropic magnetic properties from single crystal magnetization and heat capacity measurements [1]. Here we report 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 (INS) and resonant inelastic x-ray scattering (RIXS) reveal a Jz = 1/2 ground state for the Ce ion when considering the crystallographic a-axis 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 powder diffraction study in zero field reveals that on cooling from the paramagnetic state, the system first orders at TN1= 4.7 K in a longitudinal spin density wave with ordered moments along the b-axis and an incommensurate propagation vector k= (0,0.43,0). Below the lower-temperature transitionTN2= 4.48 K, the propagation vector locks to the commensurate value k= (0,0.5,0),with a so-called a lock-in transition. Our neutron single crystal 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 = 0.3 T, followed by a series of transitions before it reaches the fully field-induced ferromagnetic phase at H = 0.7 T. This explains the nature of the steps previously reported in field-dependent magnetization measurements. A very similar behaviour has also been observed for the H // [0 1 1] crystal direction.

[1] A. P. Pikul et al, Phys. Rev. B 81, 174408 (2010).