Co(x)Ni(1-x) alloy nanowires with varying Co content (0 ≤ x ≤ 0.95), having a diameter of 130 nm and length of around 20 μm, are synthesized by template-assisted electrodeposition into the nanopores of SiO(2) conformal coated hard-anodic aluminum oxide membranes. The magneto-structural properties of both single isolated nanowires and hexagonally ordered nanowire arrays of Co-Ni alloys are systematically studied by means of magneto-optical Kerr effect magnetometry and vibrating sample magnetometry, respectively, allowing us to compare different alloy compositions and to distinguish between the magnetostatic and magnetocrystalline contributions to the effective magnetic anisotropy for each system. The excellent tunable soft magnetic properties and magnetic bistability exhibited by low Co content Co-Ni nanowires indicate that they might become the material of choice for the development of nanostructured magnetic systems and devices as an alternative to Fe-Ni alloy based systems, being chemically more robust. Furthermore, Co contents higher than 51 at.% allow us to modify the magnetic behavior of Co-rich nanowires by developing well controlled magnetocrystalline anisotropy, which is desirable for data storage applications.

We present a photoemission electron microscopy method that combines magnetic imaging of the surface and of the inner magnetization in three-dimensional core-shell nanostructures. The structure investigated consists of a cylindrical nickel core that is completely surrounded by a shell of iron oxide and silicon oxide layers. The method enables one to image the magnetization configuration of the nickel core even though the shell is thicker than the mean-free path of the photoelectrons. Characteristic $L_3$ and $L_2$ edges can be observed not only in the yield of the photoelectrons emitted from the surface of the nanostructure but also in its shadow. X-ray magnetic circular dichroism in the electron yield of the x rays absorbed and transmitted by the multilayered nanowire allows for the individual imaging of the magnetization configurations of the iron oxide tube and the nickel core. The method suggests novel approaches for the characterization of the magnetic and material properties of complex three-dimensional nanostructures.

Spin-transfer torque nano-oscillators (STNO) are important candidates for several applications based on ultra-tunable microwave generation and detection. The microwave dynamics in these STNOs are induced by spin currents that are typically generated either by spin polarization in an adjacent ferromagnetic layer or through the spin Hall effect. In this paper, a 3-terminal STNO based on a magnetic tunnel junction is excited by both of these spin injection mechanisms. The combination of these two mechanisms excites the free layer into dynamic regimes beyond what can be achieved by each excitation mechanism individually, resulting in enhanced output powers, a key figures of merit for device performance. The system response can be coherently quantified as a function of the total injected spin current density. The experimental data shows an excellent consistency with this simple model and a critical spin current density of 4.52 ± 0.18 × 10⁹ħ/2 e⁻¹ Am⁻².

The magneto-thermopower is measured and correlated to the anisotropic magnetoresistance of Co-Ni alloyed nanowires with varying composition. The highest absolute and relative variation of the Seebeck coefficient in perpendicularly applied magnetic fields at room temperature is determined to be 1.5 μVK⁻¹ for Co_0.24Ni_0.76 and 8.1% for Co_0.39Ni_0.61 nanowires. Power factors of 3.7 mW/mK² have been achieved, which is competitive with common thermoelectric materials like Bi₂Te₃. For Co-Ni nanowires containing up to 39% Co, a linear relationship between the magnetic field dependent change of the Seebeck coefficient and the electrical conductivity is found.

Epitaxial thin films of the half-metallic $X_a$ compound Mn${}_2$CoGa (Hg${}_2$CuTi prototype) were prepared by dc magnetron co-sputtering with different heat treatments on MgO (001) substrates. High-quality films with a bulk magnetization of $1.95\left(5\right){\mu }_{\mathrm{B}}$ per unit cell were obtained. The $L_{3,2}$ x-ray magnetic circular dichroism spectra agree with calculations based on density functional theory (DFT) and reveal the antiparallel alignment of the two inequivalent Mn moments. X-ray magnetic linear dichroism, in good agreement with theory as well, allows us to distinguish between itinerant and local Mn moments. Based on noncollinear spin DFT, it is shown that one of the two Mn moments has local character, whereas the other Mn moment and the Co moment are itinerant.

Reported steady-state microwave emission in magnetic tunnel junction (MTJ)-based spin transfer torque nano-oscillators (STNOs) relies mostly on very thin insulating barriers [resulting in a resistance × area product (R × A) of ~1 Ωμm²] that can sustain large current densities and thus trigger large orbit magnetic dynamics. Apart from the low R × A requirement, the role of the tunnel barrier in the dynamics has so far been largely overlooked, in comparison to the magnetic configuration of STNOs. In this report, STNOs with an in-plane magnetized homogeneous free layer configuration are used to probe the role of the tunnel barrier in the dynamics. In this type of STNOs, the RF modes are in the GHz region with integrated matched output powers (P _out ) in the range of 1–40 nW. Here, P _{o u t} values up to 200 nW are reported using thicker insulating barriers for junctions with R × A values ranging from 7.5 to 12.5 Ωμm², without compromising the ability to trigger self-sustained oscillations and without any noticeable degradation of the signal linewidth (Γ). Furthermore, a decrease of two orders of magnitude in the critical current density for spin transfer torque induced dynamics (J _STT ) was observed, without any further change in the magnetic configuration.