Incommensurate short-range multipolar order parameter of phase II in Ce3Pd20Si6

TL;DR

This study reveals the incommensurate short-range multipolar order in Ce3Pd20Si6's phase II through diffuse neutron scattering, showing complex field-tunable magnetic structures linked to hidden quadrupolar moments.

Contribution

First direct observation of diffuse magnetic neutron scattering indicating multipolar order in Ce3Pd20Si6's phase II, revealing incommensurate and field-dependent magnetic structures.

Findings

Diffuse magnetic scattering observed in phase II

Incommensurate peaks under [001] magnetic field

Field-tunable complex multipolar order

Abstract

The clathrate compound Ce3Pd20Si6 is a heavy-fermion metal that exhibits magnetically hidden order at low temperatures. Reputedly, this exotic type of magnetic ground state, known as "phase II", could be associated with the ordering of Ce 4f quadrupolar moments. In contrast to conventional (dipolar) order, it has vanishing Bragg intensity in zero magnetic field and, as a result, has escaped direct observation by neutron scattering until now. Here we report the observation of diffuse magnetic neutron scattering induced by an application of magnetic field along either the [110] or the [001] direction within phase II. The broad elastic magnetic signal that surrounds the (111) structural Bragg peak can be attributed to a short-range G-type antiferromagnetic arrangement of field-induced dipoles modulated by the underlying multipolar order on the simple-cubic sublattice of Ce ions occupying the 8c Wyckoff site. In addition, for magnetic fields applied along the [001] direction, the diffuse magnetic peaks in Ce3Pd20Si6 become incommensurate, suggesting a more complex modulated structure of the underlying multipolar order that can be continuously tuned by a magnetic field.