Topological magnetic textures such as vortex cores or skyrmions are key candidates for non-volatile information processing. This exploits the texture movement by current pulses that is typically opposed by pinning. A detailed understanding of pinning is hence crucial with previous experiments being either limited in terms of controlled magnetic texture positioning or in terms of spatial resolution. Here, we use spin-polarized scanning tunneling microscopy to track a magnetic vortex core that is deliberately moved by a 3D magnetic field. The core covering about 10.000 Fe-atoms gets pinned by defects that are only a few nm apart. Reproducing the vortex path via parameter fit, we deduce the pinning potential of the defects as a mexican hat with short-range repulsive and long-range attractive part. By comparison with micromagnetic simulations, the attractive part is attributed to a local suppression of exchange interaction. The novel approach to deduce defect induced pinning potentials on the sub-nm scale is transferable to other non-collinear spin textures eventually enabling an atomic scale design of defect configurations, e.g., for reliable read-out in race-track type devices.
Directional vortex pinning at microwave frequency in YBa$_{2}$Cu$_3$O$_{7-x}$ thin films with BaZrO$_3$ nanorods
研究了用脉冲激光烧蚀法从含5%（摩尔分数）BaZrO $_3$的靶上生长的YBaPDMATHABMM CuPDMATHABMN O $_{7-x}$薄膜的各向异性和定向钉扎效应. BaZrO $_3$夹杂物自组装得到沿c轴取向的纳米棒，从而为涡旋钉扎提供了优先方向。涡旋响应的方向性研究在高交流频率与复杂的微波响应在48 GHz，作为一个功能的应用领域和领域和c轴之间的角度$θ$。复杂的微波响应不表现出任何角度缩放，这表明YBa $_2$ Cu $_3$ O $_{7-x}$的结构各向异性的补充，至少另一个优选的取向。钉扎参数$r$显示定向钉扎的证据，在围绕c轴的宽范围的角度中有效（因此归因于BZO纳米柱）。
Unusual magneto-transport of YBa2Cu3O7-d films due to the interplay of anisotropy, random disorder and nanoscale periodic pinning
我们研究了一个流形的相互作用的弹性线的空间相关性的强烈影响随机和有序钉扎之间的竞争的一般问题。这是通过磁输运实验与YBa 2 Cu 3 O 7-d薄膜，包含一个周期性的涡旋钉扎阵列通过掩蔽离子照射，除了本地随机钉扎。我们观察到的强场匹配效应表明周期性钉扎的普遍存在，并表明在匹配场中每条涡旋线都束缚在人为钉扎位点上。然而，涡玻璃化转变的维度，准2D而不是通常的3D，证据减少沿涡线的涡玻璃相关性。这也支持了一个不寻常的角度依赖的磁阻，这大大不同于玻色玻璃系统。角磁阻的定量分析使我们能够将这种行为与系统各向异性的增强联系起来，这是离子辐照的附带效应。
Ultradense Tailored Vortex Pinning Arrays in Superconducting YBa$_2$Cu$_3$O$_{7-δ}$ Thin Films Created by Focused He Ion Beam Irradiation for Fluxonics Applications
磁场以磁通量量子的形式穿透II型超导体，称为涡旋。在一个干净的超导体中，它们以六方晶格排列，而通过添加周期性的人工钉扎中心，可以实现许多其他排列。利用氦离子显微镜的聚焦束，在铜氧化物超导体$_{2}$ O $_{7-δ}$的薄膜中制备了间距为70 nm的密集钉扎中心的周期性图案。在这些超致密的kagomé样图案中，空隙导致涡流的磁笼，导致非常规的可磁化性效应，其表现为临界电流的峰值和电阻与施加磁场的最小值，最高可达$\sim 0.4\,$ T。通过对涡旋运动的分子动力学模拟，分析了不同磁场下的涡旋模式，证实了临界电流与磁场的关系。这些发现开辟了一条道路，在铜氧化物超导体的人工亚100纳米钉扎景观的控制操纵的漩涡。
