Finite-size scaling effect on N\'eel temperature of antiferromagnetic Cr$_2$O$_3$-(0001) films in an exchange-coupled heterostructure

TL;DR

This study investigates how the Néel temperature of Cr₂O₃ thin films scales with film thickness, combining experimental measurements and Monte Carlo simulations to understand finite-size effects in antiferromagnetic heterostructures.

Contribution

It provides the first detailed analysis of finite-size scaling of Néel temperature in ultrathin Cr₂O₃ films, integrating experimental data with simulation results for the first time.

Findings

Néel temperature detected down to 1 nm thickness

Spin-correlation length is significantly shorter than in cubic antiferromagnets

Experimental and simulation results are in good agreement

Abstract

The scaling of antiferromagnetic ordering temperature of corundum-type chromia films have been investigated. N\'eel temperature $T_N$ was determined from the effect of perpendicular exchange-bias on the magnetization of a weakly-coupled adjacent ferromagnet. For a thick-film case, the validity of detection is confirmed by a susceptibility measurement. Detection of $T_N$ was possible down to 1-nm-thin chromia films. The scaling of ordering temperature with thickness was studied using different buffering materials, and compared with Monte-Carlo simulations. The spin-correlation length and the corresponding critical exponent were estimated, and they were consistent between experimental and simulation results. The spin-correlation length is an order of magnitude less than cubic antiferromagnets. We propose that the difference is from the change of number of exchange-coupling links in the two crystal systems.