# Evolution of structure and magnetism across the metal-insulator transition in the pyrochlore iridate $($Nd$_{1-x}$Ca$_x)_2$Ir$_2$O$_7$

## TL;DR

This study investigates how hole-doping via Ca substitution affects the structural, electronic, and magnetic properties of Nd$_2$Ir$_2$O$_7$, revealing a filling-controlled Mott transition with minimal structural change and coupled magnetic ordering.

## Contribution

It demonstrates that Ca doping induces a Mott-like metal-insulator transition in Nd$_2$Ir$_2$O$_7$ without significant structural alterations, maintaining spin-orbit entangled Ir states and magnetic coupling.

## Key findings

- Ca substitution causes a filling-controlled Mott transition.
- Structural symmetry remains unchanged during doping.
- Magnetic ordering coincides with the metal-insulator transition.

## Abstract

We report on the evolution of the thermal metal-insulator transition in polycrystalline samples of Nd$_2$Ir$_2$O$_7$ upon hole-doping via substitution of Ca$^{2+}$ for Nd$^{3+}$. Ca substitution mediates a filling-controlled Mott-like transition with minimal resolvable structural changes and without altering site symmetry. Local structure confirms that Ca substitution does not result in local chemical phase separation, and absorption spectroscopy establishes that Ir cations maintain a spin-orbit entangled electronic configuration. The metal-insulator transition coincides with antiferromagnetic ordering on the Ir sublattice for all measured samples, and both decrease in onset temperature with Ca content. Weak low-temperature upturns in susceptibility and resistivity for samples with high Ca content suggest that Nd sublattice antiferromagnetism continues to couple to carriers in the metallic regime.