Portnichenko, P. Y., Paschen, S., Prokofiev, A., Vojta, M., Cameron, A. S., Mignot, J.-M., Ivanov, A., & Inosov, D. S. (2016). Incommensurate short-range multipolar order parameter of phase II in Ce₃Pd₂₀Si₆. Physical Review B, 94(24), Article 245132. https://doi.org/10.1103/physrevb.94.245132
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.
