Anomalous size dependence of the coercivity of nanopatterned CrGeTe3
Avia Noah, Nofar Fridman, Yishay Zur, Maya Klang, Edwin Herrera, Jose Antonio Moreno, Martin E. Huber, Hermann Suderow, Hadar Steinberg, Oded Millo, Yonathan Anahory
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.
Magnetization relaxation and search for the magnetic gap in bulk-insulating V-doped (Bi, Sb)$_2$Te$_3$
V掺杂的（Bi，Sb）$_2$ Te $_3$具有比其Cr掺杂的对应物高十倍的磁性，因此被认为是量子反常霍尔效应（QAHE）的优良系统。QAHE需要在狄拉克点处打开磁性带隙。我们没有发现这个差距的角度分辨光电子能谱学下降到1 K。通过X射线磁性圆二色性（XMCD），我们直接探测了V位和零场的磁性。的XMCD信号的磁滞曲线示出的磁场的斜坡速度上的磁化率的强烈依赖性。的XMCD信号衰减的时间尺度上的分钟，我们得出的结论有助于在狄拉克点的可检测的磁隙的情况下。
