We present synchrotron x-ray diffraction, neutron powder diffraction, and time-of-flight inelastic neutron scattering measurements on the rare earth pyrochlore oxide ${\mathrm{Nd}}_2{\mathrm{Zr}}_2{\mathrm{O}}_7$ 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 $T_{\mathrm{N}}\approx 0.4$ K with propagation vector k = (0 0 0) and an ordered moment of $1.26\left(2\right){\mu }_{\mathrm{B}}$/Nd at 0.1 K. The ordered moment is much smaller than the estimated moment of $2.65{\mu }_{\mathrm{B}}$/Nd for the local $\langle 111\rangle$ Ising ground state of ${\mathrm{Nd}}^{3+}$ $\left(J=9/2\right)$ suggesting that the ordering is partially suppressed by quantum fluctuations. The inelastic neutron scattering experiment further confirms the Ising anisotropic ground state of ${\mathrm{Nd}}^{3+}$ and also reveals its dipolar-octupolar character which possibly induces the quantum fluctuation. The crystal-field level scheme and ground state wave function have been determined.

• Received 12 October 2015
• Revised 3 December 2015

DOI:https://doi.org/10.1103/PhysRevB.92.224430