Incommensurate magnetism near quantum criticality in CeNiAsO

TL;DR

This study investigates the magnetic phase transitions in CeNiAsO using neutron scattering and muon spin rotation, revealing incommensurate and commensurate magnetic orders near quantum criticality.

Contribution

It provides detailed experimental insights into the magnetic ordering and quantum critical behavior in CeNiAsO and related compounds, highlighting the nature of incommensurate magnetism.

Findings

Incommensurate spin density wave with wave vector (0.44, 0, 0) below 8.7 K.

Co-planar commensurate order with reduced magnetic moment below 7.6 K.

Transition from incommensurate order to paramagnetic Fermi liquid at x=0.4 in CeNiAs_{1-x}P_xO.

Abstract

Two phase transitions in the tetragonal strongly correlated electron system CeNiAsO were probed by neutron scattering and zero field muon spin rotation. For $T <T_{N1}$ = 8.7(3) K, a second order phase transition yields an incommensurate spin density wave with wave vector $\textbf{k} = (0.44(4), 0, 0)$. For $T < T_{N2}$ = 7.6(3) K, we find co-planar commensurate order with a moment of $0.37(5)~\mu_B$, reduced to $30 \%$ of the saturation moment of the $|\pm\frac{1}{2}\rangle$ Kramers doublet ground state, which we establish by inelastic neutron scattering. Muon spin rotation in $\rm CeNiAs_{1-x}P_xO$ shows the commensurate order only exists for x $\le$ 0.1 so the transition at $x_c$ = 0.4(1) is from an incommensurate longitudinal spin density wave to a paramagnetic Fermi liquid.