Interplay of Ferromagnetic and Antiferromagnetic Interactions in Epitaxial Co$_3$ZnN

TL;DR

This study synthesizes epitaxial Co$_3$ZnN thin films, revealing complex magnetic behavior with competing ferromagnetic and antiferromagnetic interactions, supported by experimental measurements and theoretical simulations.

Contribution

It provides the first detailed synthesis, magnetic characterization, and theoretical analysis of epitaxial Co$_3$ZnN, highlighting the interplay of magnetic interactions in this antiperovskite nitride.

Findings

Epitaxial Co$_3$ZnN films are phase-pure and exhibit magnetic hysteresis at low temperatures.

Magnetic measurements show a transition near 25 K with competing AFM and FM interactions.

Theoretical calculations indicate a ferromagnetic ground state with close energy to AFM states.

Abstract

Antiperovskite nitrides with the general formula M$_3$N have attracted significant attention due to their tunable electronic and magnetic properties. Among them are many cobalt-based compounds predicted to exhibit high thermodynamic stability and intriguing magnetic behavior. Here, we report the synthesis and magnetic characterization of epitaxial Co$_3$ZnN thin films grown by radio frequency sputtering on SrTiO$_3$ (STO) and MgO substrates. X-ray diffraction confirms phase-pure (00l)-oriented films with cube-on-cube epitaxy on STO, with a c-lattice parameter of 3.752 angstroms. Magnetic measurements reveal clear hysteresis at 2 K with a coercive field of ~ 0.12 T and a small net moment of 0.11 ${\mu}_B$/f.u., suggesting either a canted antiferromagnetic (AFM) or ferrimagnetic (FiM) configuration. Temperature-dependent magnetization measurements show a transition near 25 K, with strong AFM interactions (Curie-Weiss $\Theta$ = -80.6 K) at high temperatures and short-range ferromagnetic correlations ($\Theta$ = +9.7 K) emerging near the transition. Complementary density functional theory (DFT) and Monte Carlo simulations indicate a ferromagnetic (FM) ground state, with the FM-AFM energy difference decreasing systematically with increasing supercell size, consistent with competition between FM and AFM/FiM interactions. These results highlight Co$_3$ZnN as a magnetically complex antiperovskite nitride with competing exchange interactions.