Erbium Probes of Magnetic Order in a Layered van der Waals Material

TL;DR

This study employs Er3+ defects embedded within a layered van der Waals material as atomic-scale probes to detect and analyze magnetic order and dynamics, revealing nanoscale magnetic phenomena beyond bulk expectations.

Contribution

It introduces a novel internal probing method using Er3+ defects for atomic-scale magnetic characterization in 2D materials, capturing local magnetic behavior through photoluminescence spectroscopy.

Findings

Er3+ photoluminescence shows thermal hysteresis near the AFM transition.

Magnetic signatures persist beyond the bulk phase boundary.

In-plane magnetic field shifts PL features, indicating ferromagnetic correlations.

Abstract

There is growing interest in characterizing magnetic order and dynamics in two-dimensional magnets, yet most efforts to date rely on external probes that interrogate the sample from tens of nanometers away and inevitably average over that length scale. Here we use internal, lattice-embedded Er3+ defects in CrSBr as atomic-scale probes, accessing their telecom-band photoluminescence with spectroscopy and temperature-dependent confocal imaging to read out magnetism from within the material. At room temperature we observe narrow, long-lived photoluminescence (PL) lines in the telecom band, characteristic of erbium emitters. Upon cooling to 3 K and reheating, the Er3+ PL intensity and excited-state lifetime display pronounced thermal hysteresis with a minimum near 132 K, at the reported antiferromagnetic (AFM) transition of CrSBr. Remarkably, we observe magnetic signatures persisting over a broader temperature range than expected from bulk benchmarks, suggesting nanoscale magnetic order that locally survives beyond the nominal phase boundary. Further, a moderate in-plane field of 0.3 T shifts the PL minimum by +8 K, which we tentatively associate to field-biased ferromagnetic correlations.