Specific heat study of spin-structural change in pyrochlore Nd$_2$Mo$_2$O$_7$

TL;DR

This study investigates how magnetic fields induce spin-structural changes in Nd$_2$Mo$_2$O$_7$ using specific heat measurements, revealing transitions from antiferromagnetic to ferromagnetic states and complex spin configurations.

Contribution

It provides detailed experimental insights into field-induced spin-structural transitions in Nd$_2$Mo$_2$O$_7$, highlighting the crossover behaviors and specific spin arrangements.

Findings

Peak shift indicating antiferromagnetic to ferromagnetic crossover

Emergence of 3-in 1-out structure at high fields

Observation of a spike-like peak suggesting spin flip transition

Abstract

By measurements of specific heat, we have investigated the magnetic field ($H$) induced spin-structural change in Nd$_2$Mo$_2$O$_7$ that shows spin-chirality-related magneto-transport phenomena. A broad peak around 2 K caused by the ordering of 2-in 2-out structure of the Nd moments at zero $H$ shifts to the lower temperature ($T$) up to around 3 T and then to the higher $T$ above around 3 T with increasing $H$ for all the direction of $H$. This is due to the crossover from antiferromagnetic to ferromagnetic arrangement between the Nd and Mo moments. While the peak $T$ increases monotonically above 3 T for $H$//[100], another peak emerges around 0.9 K at 12 T for $H$//[111], which is ascribed to the ordering of 3-in 1-out structure. For $H$//[110], a spike like peak is observed at around 3 T, which is caused perhaps by some spin flip transition.