Critical behavior of sputter-deposited magnetoelectric antiferromagnetic Cr$_2$O$_3$ films near N\'eel temperature

TL;DR

This study investigates the critical magnetic behavior of sputter-deposited Cr₂O₃ films near the Néel temperature, revealing differences in phase transition exponents and domain reversal probabilities compared to bulk single crystals.

Contribution

It provides the first detailed comparison of critical exponents and domain reversal behavior between sputter-deposited films and bulk Cr₂O₃ near the Néel temperature.

Findings

Film critical exponent near 0.49 below 293 K, changing to 1.06 near 298 K

Single-crystal critical exponent stable at 0.324

Reversal probability in films stabilizes only below 293 K

Abstract

Chromium(III) oxide is a classical collinear antiferromagnet with a linear magnetoelectric effect. We are presenting the measurements of the magnetoelectric susceptibility $\alpha$ of a sputter-deposited 500-nm film and a bulk single-crystal of Cr$_\mathrm{2}$O$_\mathrm{3}$. We investigated the magnetic phase-transition and the critical exponent $\beta$ of the sublattice magnetization near N\'eel temperature. For the films, an exponent of 0.49(1) was found below 293 K, and changed to 1.06(4) near the N\'eel temperature of 298 K. For the single-crystal, the exponent was constant at 0.324(4). We investigated the reversal probability of antiferromagnetic domains during magnetoelectric field cooling. For the sputtered films, reversal probability was zero above 298 K and stabilized only below 293 K. We attribute this behavior to formation of grains during film growth, which gives different intergrain and intragrain exchange-coupling energies. For the single-crystal, reversal probability was stabilized immediately at the N\'eel temperature of 307.6 K.