Chengyi Chen#, Hua Zhu#, En Li, Henan Chen, Huilin Xie, Jacky W. Y. Lam, Ben Zhong Tang, Wei Ji*, and Nian Lin*
Abstract:
The low spin–orbit coupling and weak hyperfine interactions make organic radicals promising components used in molecular spintronics. Triphenylmethyl is the first stable carbon-centered organic radicals discovered more than a century ago. Here we use scanning tunneling spectroscopy to study quantum transport through single triphenylmethyl radicals that are attached to a Au(111) electrode via atomic contacts of Ni atoms. The transport exhibits a Kondo resonance evidencing the unpair electron of the radical forms a spin singlet with the itinerary electrons of the electrode. Density functional theory calculations reveal an indirect Kondo screening mechanism: the itinerary electrons couple with the radical π electron via the d orbitals of the Ni atoms. These results envision a new way to regulate spin transport of organic radicals using atomic contacts in solid state spintronic devices.
Low-dimensional magnetic materials have garnered significant interest due to their unique physical properties and potential applications. Nevertheless, the synthesis of one-dimensional (1D) magnetic materials presents challenges, and the properties of these 1D materials at the single-chain limit have not been well investigated. We here explore experimentally and theoretically 1D CrX2 (X= Cl, Br, I) magnetic single-chains residing within carbon nanotubes. Single chains of CrX2 are confirmed by atomic-resolution scanning transmission electron microscopy imaging and spectroscopy analysis. Electron energy loss spectroscopy clearly reveals the high-spin state of Cr atoms within the chain. Notably, we present the first precise measurement and analysis of Cr spin state at the single-chain level, revealing that these spin states can be controlled by the local atomic bonding configuration (CrX2 versus CrX3 phases). Density functional theory calculations support the structural stability and provide the magnetic and electronic properties of the 1D CrX2 chains.
Shuo Mi#, Manyu Wang#, Bingxian Shi#, Songyang Li, Xiaoxiao Pei, Yanyan Geng, Shumin Meng, Rui Xu, Li Huang, Wei Ji, Fei Pang, Peng Cheng*, Jianfeng Guo*, and Zhihai Cheng*
Abstract:
Two-dimensional (2D) magnetic materials have predominantly exhibited easy-axis or easy-plane anisotropy and display a high sensitivity to the underlying crystal structure and lattice symmetry. Recently, an in-plane anisotropic 2D ferromagnet of FePd2Te2 has been discovered with intriguing structure and quasi-one-dimensional spin system. Here, we report a real-space investigation of its twinning structure and magnetic states using atomic/magnetic force microscopy (AFM/MFM) combined with scanning tunneling microscopy (STM). The atomic to mesoscale hierarchical structures with the orthogonal and corrugated compressive /tensile(C/T) regions are directly observed due to the intrinsic twinning-domain characteristic. The structure-related intact ferromagnetic (FM), field-induced polarized-FM states and their transitions are comparatively discussed at the mesoscale with the corresponding macroscopic magnetic measurements. Temperature- and field-dependent evolution of magnetic phase are further investigated at the FM and PM states, and summarized to obtain a unique H-T phase diagram of FePd2Te2. Our work provides key results for understanding the complicated magnetic properties of FePd2Te2, and suggests new directions for manipulating magnetic states through the atomic and mesoscale structure engineering.
Yangjin Lee#, Linxuan Li#, Weihan Zhang#, Uje Choi, Kihyun Lee, Young-Min Kim, Wei Ji*, Wu Zhou*, Kwanpyo Kim*, and Alex Zettl*
Abstract:
Low-dimensional magnetic materials have garnered significant interest due to their unique physical properties and potential applications. Nevertheless, the synthesis of one-dimensional (1D) magnetic materials presents challenges, and the properties of these 1D materials at the single-chain limit have not been well investigated. We here explore experimentally and theoretically 1D CrX2 (X= Cl, Br, I) magnetic single-chains residing within carbon nanotubes. Single chains of CrX2 are confirmed by atomic-resolution scanning transmission electron microscopy imaging and spectroscopy analysis. Electron energy loss spectroscopy clearly reveals the high-spin state of Cr atoms within the chain. Notably, we present the first precise measurement and analysis of Cr spin state at the single-chain level, revealing that these spin states can be controlled by the local atomic bonding configuration (CrX2 versus CrX3 phases). Density functional theory calculations support the structural stability and provide the magnetic and electronic properties of the 1D CrX2 chains.
Two-dimensional (2D) non-van der Waals (vdW) Cr5Te8 has attracted widespread research interest for its air stability and thickness-dependent magnetic properties. However, the growth of large-scale ultrathin 2D Cr5Te8 remains challenging. Here, we selected GaTe powder as the precursor to supply Te monomers and fabricated submillimeter 2D Cr5Te8 nanosheets. By optimizing the growth temperature and source–substrate distance (DSS), we successfully achieved Cr5Te8 nanosheets with a lateral size of up to ∼0.19 mm and corresponding thickness down to ∼4.8 nm. The role of GaTe is to enhance the efficient Te atom concentration, which promotes the lateral growth of Cr5Te8 nanosheets. Furthermore, our findings reveal the appearance of Cr5Te8 nanosheets exhibiting serrated edges and a stacked structure like those of wedding cakes. Magnetic property measurement revealed the intense out-of-plane ferromagnetism in Cr5Te8, with a Curie temperature (TC) of 172 K. This work paves the way for the controllable growth of submillimeter ultrathin 2D ferromagnetic crystals and lays the foundation for the future synthesis of millimeter ultrathin ferromagnets.
