Caffrey Nuala M, Schröder Silke, Ferriani Paolo, Heinze Stefan
Institut für Theoretische Physik und Astrophysik, Christian-Albrecht-Universität zu Kiel, Leibnizstr. 15, 24098 Kiel, Germany.
J Phys Condens Matter. 2014 Oct 1;26(39):394010. doi: 10.1088/0953-8984/26/39/394010. Epub 2014 Sep 12.
The tunneling anisotropic magnetoresistance (TAMR) effect demonstrates the sensitivity of spin-polarized electron transport to the orientation of the magnetization with respect to the crystallographic axes. As the TAMR effect requires only a single magnetic electrode, in contrast to the tunneling magnetoresistance effect, it offers an attractive route to alternative spintronic applications. In this work we consider the TAMR effect at the single-atom limit by investigating the anisotropy of the local density of states (LDOS) in the vacuum above transition-metal adatoms adsorbed on a noncollinear magnetic surface, the monolayer of Mn on W(1 1 0). This surface presents a cycloidal spin spiral ground state with an angle of 173° between neighboring spins and thus allows a quasi-continuous exploration of the angular dependence of the TAMR of adsorbed adatoms using scanning tunneling microscopy. Using first-principle calculations, we investigate the TAMR of Co, Rh and Ir adatoms on Mn/W(1 1 0) and relate our results to the magnetization-direction-dependent changes in the LDOS. The anisotropic effect is found to be enhanced dramatically on the adsorption of heavy transition-metal atoms, with values of up to 50% predicted from our calculations. This effect will be measurable even with a non-magnetic STM tip.
隧穿各向异性磁电阻（TAMR）效应表明，自旋极化电子输运对磁化方向相对于晶体轴的取向具有敏感性。与隧穿磁电阻效应不同，由于TAMR效应仅需要一个磁电极，因此它为替代自旋电子学应用提供了一条有吸引力的途径。在这项工作中，我们通过研究吸附在非共线磁性表面（W(1 1 0)上的Mn单层）上的过渡金属吸附原子上方真空中的局域态密度（LDOS）的各向异性，来考虑单原子极限下的TAMR效应。该表面呈现出一种摆线自旋螺旋基态，相邻自旋之间的夹角为173°，因此可以使用扫描隧道显微镜对吸附的吸附原子的TAMR的角度依赖性进行准连续探索。我们使用第一性原理计算，研究了Mn/W(1 1 0)上Co、Rh和Ir吸附原子的TAMR，并将我们的结果与LDOS中与磁化方向相关的变化联系起来。我们发现，在吸附重过渡金属原子时，各向异性效应会显著增强，根据我们的计算，预测值高达50%。即使使用非磁性STM尖端，这种效应也将是可测量的。
