Dipartimento di Fisica, Università di Genova and CNISM, Sede Consorziata di Genova, via Dodecaneso 33, I-16146 Genova, Italy.
CNR-SPIN, Corso Perrone 24, I-16152 Genova, Italy.
Phys Rev Lett. 2014 Jan 24;112(3):037201. doi: 10.1103/PhysRevLett.112.037201. Epub 2014 Jan 23.
We investigated the magnetic anisotropy energy of monatomic surface-step atoms in antiferromagnetic/ferromagnetic (AF/FM) epitaxial Mn/Co bilayers grown on vicinal Cu(001) surfaces. The step-induced anisotropy of the Co/Cu(001) films was quenched upon submonolayer Mn deposition, but a reentrant uniaxial surface anisotropy was observed for Mn thickness (tMn) between 1 and 2 monolayers, which disappears for Mn thickness above 2 monolayers. In the Mn/Co/Cu(001) system, Mn films undergo a tMn-dependent transition from FM to AF in the 1-2 Mn monolayer thickness range, which entails the coexistence of FM and AF Mn phases in the film. The observation of a sizeable uniaxial anisotropy exclusively in the Mn-thickness range of coexistence of the FM and AF phases points out the crucial role of the boundaries between FM and AF regions within the Mn film. A symmetry-breaking mechanism of a magnetic type, rather than a purely geometric one, is therefore proposed as the origin of the reentrant anisotropy.
我们研究了在倾斜 Cu(001) 表面上生长的反铁磁/铁磁 (AF/FM) 外延 Mn/Co 双层膜中单原子表面台阶原子的磁各向异性能。在亚单层 Mn 沉积后，Co/Cu(001) 薄膜的台阶诱导各向异性被猝灭，但在 Mn 厚度 (tMn) 在 1 到 2 单层之间时，观察到再入各向同性表面各向异性，当 Mn 厚度超过 2 单层时，这种各向异性消失。在 Mn/Co/Cu(001) 体系中，Mn 薄膜在 1-2 Mn 单层厚度范围内经历了从 FM 到 AF 的 tMn 依赖性转变，这导致了薄膜中 FM 和 AF Mn 相的共存。在 FM 和 AF 相共存的 Mn 厚度范围内仅观察到可观的各向同性各向异性，这表明 Mn 膜中 FM 和 AF 区域之间的边界起着至关重要的作用。因此，提出了一种磁型而非纯几何型的对称破缺机制作为再入各向异性的起源。
