Muon spin relaxation and neutron diffraction investigations of quadrupolar and magnetically ordered states of YbRu2Ge2

TL;DR

This study investigates the magnetic and quadrupolar phase transitions of YbRu2Ge2 using muon spin relaxation and neutron diffraction, revealing incommensurate antiferromagnetic order below 8 K and multiple phase transitions.

Contribution

It provides detailed experimental evidence of the magnetic and quadrupolar states in YbRu2Ge2, including the nature of magnetic ordering and phase transitions, using combined muon spin relaxation and neutron diffraction techniques.

Findings

Incommensurate antiferromagnetic order below 8 K with q = [0.352, 0, 0]

Multiple phase transitions at T0 ~ 10 K, T1 ~ 6.5 K, T2 ~ 5.5 K

No magnetic order detected above 8 K in μSR, but neutron diffraction confirms magnetic Bragg peaks below 8 K.

Abstract

The magnetic and quadrupolar ordered states of polycrystalline YbRu2Ge2 have been investigated using zero-field muon spin relaxation ({\mu}SR) and neutron diffraction measurements. Specific heat measurements show three successive phase transitions, with decreasing temperature from a paramagnetic to a quadrupolar state at T0 ~ 10 K, from the quadrupolar to a magnetic state at T1 ~ 6.5 K and a possible change in the magnetic ground state at T2 ~ 5.5 K. Clear evidence for the magnetic transition below 7 K (spectrum at 8 K reveals paramagnetic state) and a likely change in the magnetic structure near 5.8 K is observed in the zero-field {\mu}SR measurements. The {\mu}SR data, however, do not reveal any signature of magnetic order in the temperature range 8 - 45 K. This result is further supported by neutron diffraction measurements, where clear magnetic Bragg peaks have been observed below 8 K, but not above it. Below 8 K, the magnetic Bragg peaks can be characterized by an incommensurate antiferromagnetic ordering with the propagation vector q = [0.352, 0, 0] and the magnetic moment 2.9(3) {\mu}B of Yb along the b-axis. These results are discussed in terms of quadrupolar ordered and magnetically ordered states.