Anomalous size dependence of the coercivity of nanopatterned CrGeTe3

TL;DR

This study reveals an unusual size-dependent coercivity in CrGeTe3 nanoislands, where smaller islands have higher coercivity, indicating edge-dominated magnetic anisotropy and complex domain structures.

Contribution

The paper uncovers an anomalous inverse scaling of coercivity with island size in CrGeTe3, highlighting the role of edge states in low-dimensional magnetism.

Findings

Smaller nanoislands exhibit higher coercivity.

Coercivity scales inversely with island width and thickness (1/ wd).

Large islands show multi-domain structures with zero net remnant field.

Abstract

The coercivity of single-domain magnetic nanoparticles typically decreases with the nanoparticle size and reaches zero when thermal fluctuations overcome the magnetic anisotropy. Here, we used SQUID-on-tip microscopy to investigate the coercivity of square-shaped CrGeTe3 nanoislands with a wide range of sizes and width-to-thickness aspect ratios. The results reveal an anomalous size-dependent coercivity, with smaller islands exhibiting higher coercivity. The nonconventional scaling of the coercivity in CrGeTe3 nanoislands was found to be inversely proportional to the island width and thickness (1 over wd). This scaling implies that the nanoisland magnetic anisotropy is proportional to the perimeter rather than the volume, suggesting a magnetic edge state. In addition, we observe that 1600 nm wide islands display multi-domain structures with zero net remnant field, corresponding to the magnetic properties of pristine CrGeTe3 flakes. Our findings highlight the significant influence of edge states on the magnetic properties of CrGeTe3 and deepen our understanding of low-dimensional magnetic systems.