A novel type of splayed ferromagnetic order observed in Yb2Ti2O7

TL;DR

This study reports the discovery of a new splayed ferromagnetic order in Yb2Ti2O7, revealing a distinct magnetic configuration with implications for understanding pyrochlore magnetism.

Contribution

It provides the first neutron diffraction evidence of magnetic Bragg reflections in Yb2Ti2O7 and characterizes its unique splayed ferromagnetic order.

Findings

Yb2Ti2O7 exhibits magnetic Bragg reflections at 60 mK.

The magnetic structure is a splayed ferromagnet with all-in--all-out components.

The magnetic configuration differs from Yb2Sn2O7, showing a unique perpendicular moment arrangement.

Abstract

The pyrochlore insulator Yb2Ti2O7 has attracted the attention of experimentalists and theoreticians alike for about 15 years. Conflicting neutron diffraction data on the possible existence of magnetic Bragg reflections at low temperature have been published. Here we report the observation of magnetic Bragg reflections by neutron powder diffraction at 60 mK. The magnetic diffraction pattern is analyzed using representation theory. We find Yb2Ti2O7 to be a splayed ferromagnet as reported for Yb2Sn2O7, a sibling compound with also dominating ferromagnetic interactions as inferred from the positive Curie-Weiss temperature. However, the configuration of the magnetic moment components perpendicular to the easy axis is of the all-in--all-out type in Yb2Ti2O7 while it is two-in--two-out in Yb2Sn2O7. An overall experimental picture of the magnetic properties emerges.