Tuning quantum well states (QWSs) to govern physical properties in nanoscale leads to the development of advanced electronic devices. Here, we propose that QWSs can be engineered to control magnetocrystalline anisotropy energy (MCAE) which dominates the magnetization orientation (that is, the easy axis) of a ferromagnetic thin film. We investigate from first-principles the MCAE of the bcc Fe film on an Ag substrate. The calculated MCAE oscillates largely as Fe thickness increases agreeing well with experiments, and reaches oscillation extremes as the Fe d-orbital QWSs approach the Fermi level (E_F). Crucially, we find that this phenomenon stems from the combined effect of intrinsic spin-orbit interaction (SOI) and Rashba SOI field on the Fe QWSs, which modulates the density of states at E_F as the Fe thickness varies. Moreover, this effect offers a way to tune not only the strength of magnetic anisotropy but also the easy axis of a Fe film by shifting E_F within ten meV via moderately charge injection, which could realize advanced memory devices with ultra-low power consumption.

调节量子阱状态（QWS）以控制纳米级的物理性质导致了高级电子设备的发展。在这里，我们建议可以设计QWS，以控制主导铁磁薄膜磁化方向（即易轴）的磁晶各向异性能（MCAE）。我们从第一原理出发，研究了在Ag衬底上的bcc Fe膜的MCAE。随着Fe厚度的增加，计算得出的MCAE大幅波动，与实验吻合得很好；随着Fe d轨道QWS接近费米能级（E _F），计算出的MCAE达到极限振荡。至关重要的是，我们发现此现象源于内在自旋轨道相互作用（SOI）和Rashba SOI场对Fe QWSs的联合作用，该作用调节了铁电量子点处的态密度。E _F随着铁厚度的变化而变化。此外，该效果提供了一种通过适度的电荷注入使E _F偏移10 meV以内的方法，不仅可以调整磁各向异性的强度，而且可以调整Fe膜的易轴，从而可以实现具有超低功耗的先进存储器件。