Optical Detection of Weak Magnetic Transitions via Photoluminescence in Cr‐Doped Van Der Waals Antiferromagnets

Abstract 2D van der Waals antiferromagnets, MPX 3 (M = Fe, Cr, and Mn; X = S and Se), are promising candidates for spintronic devices owing to their advantageous structural and magnetic properties. However, their insulating properties and high‐field requirements make magnetic characterization in 2D MPX 3 challenging. Fortunately, the correlation between magnetic and optical properties in MPX 3 crystals provides an optical approach to investigate their magnetic properties. Herein, Cr atoms are used to modulate the magnetic properties of MnPS 3 , with photoluminescence (PL) techniques used to investigate the effect of doping. Results show a new PL peak in Cr‐doped MnPS 3 crystals, with distinct temperature‐dependent PL behaviors compared to the undoped host. The influence of doping concentration, temperature, and thickness on PL is investigated. Surprisingly, even when long‐range magnetic ordering is completely disrupted, the temperature‐dependent PL properties of Cr‐doped MnPS 3 (Cr x Mn 1 − x PS 3 ) still follow the Néel transition behavior of MnPS 3 , showing the presence of local antiferromagnetism in Cr x Mn 1 − x PS 3 . This study further substantiates the correlation between magnetic ordering and PL in MnPS 3 and demonstrates that PL is a powerful tool for detecting weak local magnetism in 2D MPX 3 crystals.