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We report on the magnetic properties of HoCo dimers as a model system for the smallest intermetallic transition metal-lanthanide compound. The dimers are adsorbed on ultrathin MgO(100) films grown on Ag(100). New for $4f$ elements, we detect inelastic excitations with scanning tunneling microscopy and prove by their behaviour in applied magnetic field that they are spin-excitations. In combination with density functional theory and spin Hamiltonian analysis we determine the magnetic level distribution, as well as sign and magnitude of the exchange interaction between the two atoms. In contrast to typical $4f-3d$ bulk compounds, we find ferromagnetic coupling in the dimer.

Spin-polarized scanning tunneling microscopy (SP-STM) measures tunnel magnetoresistance (TMR) with atomic resolution. While various methods for achieving SP probes have been developed, each is limited with respect to fabrication, performance, and allowed operating conditions. In this study, we present the fabrication and use of SP-STM tips made from commercially available antiferromagnetic $\rm{Mn_{88}Ni_{12}}$ foil. The tips are intrinsically SP, which is attractive for exploring magnetic phenomena in the zero field limit. The tip material is relatively ductile and straightforward to etch. We benchmark the conventional STM and spectroscopic performance of our tips and demonstrate their spin sensitivity by measuring the two-state switching of holmium single atom magnets on MgO/Ag(100).

We report on the magnetic properties of Fe and Co adatoms on a Cu$_{2}$N/Cu(100)-$c(2 \times 2)$ surface investigated by x-ray magnetic dichroism measurements and density functional theory (DFT) calculations including the local coulomb interaction. We compare these results with properties formerly deduced from STM spin excitation spectroscopy (SES) performed on the individual adatoms. In particular we focus on the values of the local magnetic moments determined by XMCD compared to the expectation values derived from the description of the SES data.The angular dependence of the projected magnetic moments along the magnetic field, as measured by XMCD, can be understood on the basis of the SES Hamiltonian. In agreement with DFT, the XMCD measurements show large orbital contributions to the total magnetic moment for both magnetic adatoms.

We study the coexistence of strain- and charge-mediated magnetoelectric coupling in a cobalt (0-7 nm) wedge on ferroelectric [Pb(Mg$_{1/3}$/Nb$_{2/3}$)O$_{3}$]$_{0.68}$-[PbTiO$_{3}$]$_{0.32}$ (011) using surface-sensitive x-ray magnetic circular dichroism spectroscopy at the Co L$_{3,2}$ edges. Three distinct electric field driven remanent magnetization states can be set in the Co film at room temperature. Ab-initio density functional theory calculations unravel the relative contributions of both strain and charge to the observed magnetic anisotropy changes illustrating magnetoelectro-elastic coupling at artificial multiferroic interfaces.

We combine density functional theory, x-ray magnetic circular dichroism, multiplet calculations, and scanning tunneling spectroscopy to assess the magnetic properties of Fe atoms adsorbed on a thin layer of MgO(100) on Ag(100). Despite the strong axial field due to the O ligand, the weak cubic field induced by the four-fold coordination to Mg atoms entirely quenches the first order orbital moment. This is in marked contrast to Co, which has an out-of-plane orbital moment of $L_z = \pm 3$ that is protected from mixing in a cubic ligand field. The spin-orbit interaction restores a large fraction of the Fe orbital moment leading a zero-field splitting of $14.0 \pm 0.3$~meV, the largest value reported for surface adsorbed Fe atoms., Comment: 6 pages, 4 figures

Possible ferromagnetism induced in otherwise non-magnetic materials has been motivating intense research in complex oxide heterostructures. Here we show that a confined magnetism is realized at the interface between SrTiO3 and two insulating polar oxides, BiMnO3 and LaAlO3. By using polarization dependent x-ray absorption spectroscopy, we find that in both cases the magnetic order is stabilized by a negative exchange interaction between the electrons transferred to the interface and local magnetic moments. These local magnetic moments are associated to Ti3+ ions at the interface itself for LaAlO3/SrTiO3 and to Mn3+ ions in the overlayer for BiMnO3/SrTiO3. In LaAlO3/SrTiO3 the induced magnetic moments are quenched by annealing in oxygen, suggesting a decisive role of oxygen vacancies in the stabilization of interfacial magnetism., Comment: 5 pages, 4 figures