Robust noncoplanar magnetism in band filling-tuned (Nd$_{1-x}$Ca$_x$)$_2$Mo$_2$O$_7$

TL;DR

This study investigates the stability of noncoplanar, canted ferromagnetic order in (Nd$_{1-x}$Ca$_{x}$)$_2$Mo$_2$O$_7$, showing how magnetic interactions evolve with calcium doping and identifying a transition to a spin-glass metallic state.

Contribution

It demonstrates the persistence of canted ferromagnetic order in Ca-doped Nd$_2$Mo$_2$O$_7$ and details the evolution of magnetic couplings with doping, revealing a transition to spin-glass behavior.

Findings

Canted ferromagnetic order remains stable for x ≤ 0.15.

Magnetic couplings change sign above x=0.22.

Transition from ferromagnetic to spin-glass metallic state occurs at higher doping.

Abstract

In the metallic pyrochlore Nd$_2$Mo$_2$O$_7$, the conducting Molybdenum sublattice adopts canted, yet nearly collinear ferromagnetic order with nonzero scalar spin chirality. The chemical potential may be controlled by replacing Nd$^{3+}$ with Ca$^{2+}$, while introducing only minimal additional disorder to the conducting states. Here, we demonstrate the stability of the canted ferromagnetic state, including the tilting angle of Molybdenum spins, in (Nd$_{1-x}$Ca$_{x}$)$_2$Mo$_2$O$_7$ (NCMO) with $x\le 0.15$ using magnetic susceptibility measurements. Mo-Mo and Mo-Nd magnetic couplings both change sign above $x=0.22$, where the canted ferromagnetic state gives way to a spin-glass metallic region. Contributions to the Curie-Weiss law from two magnetic sublattices are separated systematically.