Magnetic skyrmions are promising candidates for the next generation of spintronic devices due to their small size and topologically protected structure. One challenge for using these magnetic states in applications lies on controlling the nucleation process and stabilization that usually requires an external force. Here, we report on the evidence of skyrmions in unpatterned symmetric Pd/Co/Pd multilayers at room temperature without prior application of neither electric current nor magnetic field. Decreasing the ferromagnetic interlayer thickness, the tuning of the physical properties across the ferromagnetic/non-magnetic interface gives rise to a transition from worm like domains patterns to isolated skyrmions as demonstrated by magnetic force microscopy. On the direct comparison of the measured and simulated skyrmions size, the interfacial Dzyaloshinskii-Moriya interaction (iDMI) was estimated, reveling that isolated skyrmions are just stabilized at zero magnetic field taking into account non-null values of iDMI. Our findings provide new insights towards the use of stabilized skyrmions for room temperature devices in nominally symmetric multilayers.

In the zero-field-cooled exchange bias (ZEB) effect, the unidirectional magnetic anisotropy is set at low temperatures even when the system is cooled in the absence of an external magnetic field. ${\mathrm{La}}_{1.5}{\mathrm{Sr}}_{0.5}{\mathrm{CoMnO}}_6$ stands out as presenting the largest ZEB reported so far, while for ${\mathrm{La}}_{1.5}{\mathrm{Ca}}_{0.5}{\mathrm{CoMnO}}_6$ the exchange bias field ($H_{\text{EB}}$) is one order of magnitude smaller. Here we show that ${\mathrm{La}}_{1.5}{\mathrm{Ba}}_{0.5}{\mathrm{CoMnO}}_6$ also exhibits a pronounced shift of its magnetic hysteresis loop, with an intermediate $H_{\text{EB}}$ value with respect to Ca- and Sr-doped samples. To figure out the microscopic mechanisms responsible for this phenomenon, these compounds were investigated by means of synchrotron x-ray powder diffraction, Raman spectroscopy, muon spin rotation and relaxation, ac and dc magnetization, x-ray absorption spectroscopy (XAS), and x-ray magnetic circular dichroism (XMCD). The parent compound ${\mathrm{La}}_2{\mathrm{CoMnO}}_6$ was also studied for comparison as a reference of a non-ZEB material. Our results show that the Ba-, Ca-, and Sr-doped samples present a small amount of phase segregation, and that the ZEB effect is strongly correlated to the system's structure. We also observed that mixed valence states ${\mathrm{Co}}^{2+}/{\mathrm{Co}}^{3+}$ and ${\mathrm{Mn}}^{4+}/{\mathrm{Mn}}^{3+}$ are already present at the ${\mathrm{La}}_2{\mathrm{CoMnO}}_6$ parent compound, and that ${\mathrm{Ba}}^{2+}/{\mathrm{Ca}}^{2+}/{\mathrm{Sr}}^{2+}$ partial substitution at the ${\mathrm{La}}^{3+}$ site leads to a large increase of Co average valence, with a subtle augmentation of Mn formal valence. Estimates of the Co and Mn valences from the $L$-edge XAS indicate the presence of oxygen vacancies in all samples ($0.05\le \delta \le 0.1$). Our XMCD results show a great decrease of Co moment for the doped compounds, and they indicate that the shift of the hysteresis curves for these samples is related to uncompensated antiferromagnetic coupling between Co and Mn.

This article shows that the spin-to-charge current conversion in single-layer graphene (SLG) by means of the inverse Rashba-Edelstein effect (IREE) is made possible with the integration of this remarkable 2D material with the unique ferrimagnetic insulator yttrium iron garnet ($\mathrm{YIG}={\mathrm{Y}}_3\mathrm{F}{\mathrm{e}}_5{\mathrm{O}}_{12}$) as well as with the ferromagnetic metal permalloy ($\mathrm{Py}=\mathrm{N}{\mathrm{i}}_{81}\mathrm{F}{\mathrm{e}}_{19}$). By means of x-ray absorption spectroscopy and magnetic circular dichroism techniques, we show an induced magnetic moment in carbon atoms of the SLG due to the proximity effect with the magnetic layer. The spin currents are generated in the magnetic layer by spin pumping from microwave-driven ferromagnetic resonance and are detected by a dc voltage along the graphene layer, at room temperature. The spin-to-charge current conversion, occurring at the graphene layer, is explained by the extrinsic spin-orbit interaction induced by the proximity effect with the ferromagnetic layer. The results obtained for the SLG/YIG and SLG/Py systems confirm very similar values for the IREE parameter, which are larger than the values reported in previous studies for SLG. We also report systematic investigations of the electronic and magnetic properties of SLG/YIG by means of scanning tunneling microscopy.

We investigate the angular dependence of asymmetric magnetoimpedance of NiFe/IrMn multilayers and explore the possibility of tuning the linear region of the magnetoimpedance curves by modifying the angle between the applied external magnetic field and exchange bias field, and probe current frequency. We quantify the sensitivity by calculating the ratio | Δ Z | / | Δ H | at low magnetic fields as a function of the frequency for samples cut with different orientations and show that considerable values in the linear region around zero field can be reached. The results extend the possibilities for application of exchange biased magnetoimpedance multilayers as probe element for the development and improvement of auto-biased linear magnetic field sensors.