Investigation of the magnetic structure and crystal field states of pyrochlore antiferromagnet Nd2Zr2O7

TL;DR

This study combines diffraction and neutron scattering techniques to elucidate the magnetic structure and crystal field states of Nd2Zr2O7, revealing an all-in/all-out antiferromagnetic order with quantum fluctuations affecting the magnetic moment.

Contribution

It provides detailed experimental insights into the magnetic ordering and crystal field states of Nd2Zr2O7, highlighting the role of quantum fluctuations in its magnetic properties.

Findings

Long-range all-in/all-out antiferromagnetic order below 0.4 K

Ordered magnetic moment smaller than expected, indicating quantum fluctuations

Identification of a dipolar-octupolar Kramers doublet ground state

Abstract

We present synchrotron x-ray diffraction, neutron powder diffraction and time-of-flight inelastic neutron scattering measurements on the rare earth pyrochlore oxide Nd2Zr2O7 to study the ordered state magnetic structure and cystal field states. The structural characterization by high-resolution synchrotron x-ray diffraction confirms that the pyrochlore structure has no detectable O vacancies or Nd/Zr site mixing. The neutron diffraction reveals long range all-in/all-out antiferromagnetic order below T_N ~ 0.4 K with propagation vector k = (0 0 0) and an ordered moment of 1.26(2) \mu_B/Nd at 0.1 K. The ordered moment is much smaller than the estimated moment of 2.65 \mu_B/Nd for the local <111> Ising ground state of Nd3+ (J=9/2) suggesting that the ordering is partially suppressed by quantum fluctuations. The strong Ising anisotropy is further confirmed by the inelastic neutron scattering data which reveals a well-isolated dipolar-octupolar type Kramers doublet ground state. The crystal field level scheme and ground state wavefunction have been determined.