Magnetic structure and crystal field states of antiferromagnetic CeNiGe$_3$: Neutron scattering and $\mu$SR investigations

TL;DR

This study investigates the magnetic structure and crystal field states of antiferromagnetic CeNiGe$_3$ using neutron scattering and $$SR, revealing an incommensurate helical magnetic order and detailed CEF excitations.

Contribution

The paper provides a comprehensive microscopic analysis of CeNiGe$_3$, including its magnetic structure, CEF excitations, and muon spin relaxation, with new insights into its incommensurate magnetic order and CEF parameters.

Findings

CeNiGe$_3$ exhibits incommensurate helical antiferromagnetic order with $T_N \\approx 5.2$ K.

Two CEF excitations identified at 9.17 meV and 18.42 meV.

Long-range AFM order confirmed by $$SR with three internal field frequencies.

Abstract

We present the results of microscopic investigations of antiferromagnetic CeNiGe$_3$, using neutron powder diffraction (NPD), inelastic neutron scattering (INS), and muon spin relaxation ($\mu$SR) measurements. CeNiGe$_3$ crystallizes in a centrosymmetric orthorhombic crystal structure (space group: $Cmmm$) and undergoes antiferromagnetic (AFM) ordering. The occurrence of long-range AFM ordering at $T_{\rm N} \approx 5.2$~K is confirmed by magnetic susceptibility, heat capacity, neutron diffraction, and $\mu$SR measurements. The NPD data characterize the AFM state with an incommensurate helical magnetic structure having a propagation vector $k$ = (0, 0.41, 1/2). In addition, INS measurements at 10~K identified two crystal electric field (CEF) excitations at 9.17~meV and 18.42~meV. We analyzed the INS data using a CEF model for an orthorhombic environment of Ce$^{3+}$ ($J=5/2$) and determined the CEF parameters and ground state wavefunctions of CeNiGe$_3$. Moreover, zero-field $\mu$SR data for CeNiGe$_3$ at $T< T_{\rm N}$ show long-range AFM ordering with three distinct oscillation frequencies corresponding to three different internal fields at the muon sites. The internal fields at the muon-stopping sites have been further investigated using density functional theory calculations.