Canted antiferromagnetism in high purity $\mathrm{NaFeF_3}$ prepared by a novel wet-chemical synthesis method

TL;DR

This paper introduces a new wet-chemical synthesis method for high-purity NaFeF3, revealing its canted antiferromagnetic structure with weak ferromagnetism confirmed by magnetometry and neutron diffraction.

Contribution

A novel wet-chemical synthesis technique for large-volume, high-purity NaFeF3 and detailed structural and magnetic characterization of its canted antiferromagnetic state.

Findings

NaFeF3 has a Neel temperature of 90 K.

Weak ferromagnetism is inherent to NaFeF3.

Magnetic structure is a weakly canted G-type antiferromagnet.

Abstract

We report a novel synthesis method for, and structural and magnetic characterization of the fluoroperovskite $\mathrm{NaFeF_3}$. We have developed a wet-chemical method that allows preparation of large volumes of air-sensitive fluoroperovskites with high purity. $\mathrm{NaFeF_3}$ has a N\'eel temperature ($T_N$) of 90 K and a Weiss constant ($\theta$) of -124 K, corresponding to dominant antiferromagnetic interactions. Below $T_N$, a slight difference is observed between zero-field and field cooled samples, indicating spin-canting and weak ferromagnetism. AC magnetometry confirms that weak ferromagnetism is inherent to $\mathrm{NaFeF_3}$ and not due to impurities. From powder neutron diffraction data, we describe the magnetic structure precisely as a weakly canted G-type (magnetic space group $Pn'ma'$). A ferromagnetic component is allowed in $Pn'ma'$, however, this component may be absent in zero magnetic fields and is too small to be confirmed on the basis of powder neutron diffraction data.