Excitation of finite chains of magnetic atoms adsorbed on a surface by tunnelling electrons from an STM (Scanning Tunnelling Microscope) tip is studied using a Heisenberg Hamiltonian description of the magnetic couplings along the chain and a strong coupling approach of inelastic tunnelling. The excitation probability of the magnetic levels is very high and the excitation spectra in chains of different lengths are very similar. The excitations in finite chains can be considered as spin waves quantized in the finite object. The energy and momentum spectra of the spin waves excited in the idealized infinite chain by tunnelling electrons are determined from the results on the finite chains. Both ferro- and antiferromagnetic couplings are considered, leading to very different results. In particular, in the anti-ferromagnetic case, excitations linked to the entanglement of the chain ground state are evidenced.
Electrical transport properties of nanostructured ferromagnetic perovskite oxides La_0.67Ca_0.33MnO_3 and La_0.5Sr_0.5CoO_3 at low temperatures (5 K > T >0.3 K) and high magnetic field
Magnetic field dependent variable range hopping behaviour in resistivity at low temperatures in polycrystalline colossal magnetoresistive manganites: evidence of spin polarised tunnelling
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Department of Physics, University of Basel（巴塞尔大学物理系）
High-spin orbital interactions across van der Waals gaps controlling the interlayer ferromagnetism in van der Waals ferromagnets
我们研究了什么样的相互作用控制范德华铁磁体（如Fe 3-xGeTe 2，Cr2 Ge 2 Te 6，CrI 3和VI 3）中层间耦合的符号和强度，发现范德华能隙中的高自旋轨道相互作用是理解其铁磁性的关键。Fe_（3-x）GeTe_2Cr_2Ge_2 Te_6和Cr_I_3的层间铁磁耦合是由高自旋双轨道双电子不稳定性控制的，而VI_3的层间铁磁耦合是由高自旋四轨道双电子不稳定性控制的。这些相互作用解释了范德瓦尔斯铁磁体中许多看似令人困惑的观测结果。
RbEu(Fe$_{1-x}$Ni$_x$)$_4$As$_4$: From a ferromagnetic superconductor to a superconducting ferromagnet
本征空穴掺杂的RbEuFe $_4$ As $_4$在$T_{\mathrm{sc}}=36.5$ K下表现出体超导电性，在$T_\mathrm{m}=15$ K下表现出Eu亚晶格中的铁磁有序性.在这里，我们提出了一个空穴补偿的研究，通过引入额外的巡回电子通过Ni替代的铁磁超导体RbEuFe $_4$作为$_4$与$T_{\mathrm{sc}}>T_{\mathrm{m}}$。随着Ni的掺杂，$T_{\mathrm{sc}}$迅速降低，Eu自旋铁磁性及其$T_{\mathrm{m}}$保持不变。因此，系统RbEu（Fe $_{1-x}$ Ni $_x$）$_4$ As $_4$转变为超导铁磁体，其中$T_{\mathrm{m}}>T_{\mathrm{sc}}$为$0.07\leq x\leq0.08$。超导铁磁体的出现归因于Eu $^{2+}$自旋与超导Cooper对之间的退耦。建立了超导和磁相图，其中还包括恢复但抑制自旋密度波状态。
