Structural and Magnetic Investigations of Single-Crystals of the Neodymium Zirconate Pyrochlore, Nd2Zr2O7

TL;DR

This study investigates the structural and magnetic properties of high-quality Nd2Zr2O7 single crystals, revealing no magnetic order down to 0.5 K, ferromagnetic coupling, Ising anisotropy, and thermal anomalies, using various diffraction, scattering, and magnetic measurements.

Contribution

The paper provides detailed structural and magnetic characterizations of Nd2Zr2O7 single crystals, including crystal field analysis and exchange interactions, with no prior comprehensive study on these properties.

Findings

No magnetic ordering down to 0.5 K.

Ferromagnetic coupling between Nd moments.

Presence of a thermal anomaly below 7 K.

Abstract

We report structural and magnetic properties studies of large high quality single-crystals of the frustrated magnet, Nd$_2$Zr$_2$O$_7$. Powder x-ray diffraction analysis confirms that Nd$_2$Zr$_2$O$_7$ adopts the pyrochlore structure. Room-temperature x-ray diffraction and time-of-flight neutron scattering experiments show that the crystals are stoichiometric in composition with no measurable site disorder. The temperature dependence of the magnetic susceptibility shows no magnetic ordering at temperatures down to 0.5 K. Fits to the magnetic susceptibility data using a Curie-Weiss law reveal a ferromagnetic coupling between the Nd moments. Magnetization versus field measurements show a local Ising anisotropy along the <111> axes of the Nd$^{3+}$ ions in the ground state. Specific heat versus temperature measurements in zero applied magnetic field indicate the presence of a thermal anomaly below $T\sim7$ K, but no evidence of magnetic ordering is observed down to 0.5 K. The experimental temperature dependence of the single-crystal bulk dc susceptibility and isothermal magnetization are analyzed using crystal field theory and the crystal field parameters and exchange coupling constants determined.