Emergent magnetism at transition-metal-nanocarbon interfaces
Emergent magnetism at transition-metal-nanocarbon interfaces
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DOI：
10.1073/pnas.1620216114
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发表时间：
2017-05-30
影响因子：
11.1
通讯作者：
Cespedes, Oscar
中科院分区：
文献类型：
--
作者：
Al Ma'Mari, Fatma;Rogers, Matthew;Cespedes, Oscar
在金属-分子界面处的电荷转移可用于设计具有紧急磁化的多功能混合物，其可提供对传统磁体和装置的生态友好和可调谐的替代方案。在这里，我们调查在这些接口处产生的磁性的起源，通过使用不同的技术来探测3D和5D金属膜，如Sc，Mn，Cu和Pt与富勒烯和RF溅射碳层接触。这些系统表现出小的各向异性和双折射率以及高的居里点。低能μ子自旋谱在Cu和Sc-C-60多层膜显示了快速的自旋去极化和振荡归因于不均匀的局部磁场靠近金属-碳界面。碳层的杂化状态起着至关重要的作用，我们观察到增加的磁化作为sp（3）轨道退火到sp（2）-π石墨态溅射碳/铜多层膜。X射线磁性圆二色性（XMCD）测量在C-60层的碳K边缘与Sc膜接触显示自旋极化在最低未占分子轨道（LUMO）和更高的π *-分子水平，而在西格玛 *-共振的二色性很小或不存在。这些结果支持通过从金属和dz-pi杂化的电荷转移介导的相互作用的想法。薄膜碳基磁体可以允许使用电光信号在金属表面操纵自旋有序，在计算、传感器和其他多功能磁性设备中具有潜在的应用。
Charge transfer at metallo-molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc-C-60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo-carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp(3) orbitals are annealed into sp(2)-pi graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C-60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher pi*-molecular levels, whereas the dichroism in the sigma*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz-pi hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices.