The fabrication of large area binary magnetic nanostructures made from one or two ferromagnetic materials (Ni and Ni80Fe20) is reported using self‐aligned shadow deposition technique. The static and ...dynamic properties are characterized using magneto‐optical Kerr effects (MOKE) and broadband ferromagnetic resonance spectroscopy. Compared with Ni80Fe20 nanomagnets made using a conventional lithographic technique from identical resist templates, tunable magnetization switching is observed with a marked increase in the coercive field and more adjustable dynamic response for the Ni80Fe20/Ni80Fe20 and Ni/Ni80Fe20 binary structures. The results are validated by direct domain imaging using magnetic force microscopy and micromagnetic simulations.
The fabrication of large area binary magnetic nanostructures made from one or two ferromagnetic materials (Ni and Ni80Fe20) is reported using a self‐aligned shadow deposition technique. Tunable magnetization switching and an adjustable dynamic response is observed for the binary structures. The results are validated by direct domain imaging using magnetic force microscopy and micromagnetic simulations.
Topological surface states (TSSs) in a topological insulator are expected to be able to produce a spin-orbit torque that can switch a neighboring ferromagnet. This effect may be absent if the ...ferromagnet is conductive because it can completely suppress the TSSs, but it should be present if the ferromagnet is insulating. This study reports TSS-induced switching in a bilayer consisting of a topological insulator Bi
Se
and an insulating ferromagnet BaFe
O
. A charge current in Bi
Se
can switch the magnetization in BaFe
O
up and down. When the magnetization is switched by a field, a current in Bi
Se
can reduce the switching field by ~4000 Oe. The switching efficiency at 3 K is 300 times higher than at room temperature; it is ~30 times higher than in Pt/BaFe
O
. These strong effects originate from the presence of more pronounced TSSs at low temperatures due to enhanced surface conductivity and reduced bulk conductivity.
Pure spin currents have been ubiquitous in contemporary spintronics research. Despite its profound physical and technological significance, the detection of pure spin current has largely remained ...indirect, which is usually achieved by probing spin-transfer torque effects or spin-to-charge conversions. By using scanning transmission x-ray microscopy, we report the direct detection and spatial mapping of spin accumulation in a nonmagnetic Cu layer without any direct charge current injection. Such a pure spin current is induced by spin pumping from a Ni_{80}Fe_{20} layer and is not accompanied by concomitant charge motion. The observed frequency dependence indicates that the signal is dominated by a coherent, pure spin current, but the magnitude of the spin accumulation suggests also possible additional thermal contributions. Our technique takes advantage of the x-ray magnetic circular dichroism and the synchronization of microwave with x-ray pulses, which together provide a high sensitivity for probing transient magnetic moment. From the detected x-ray signals, we observe two distinct resonance modes induced by spin pumping, which, based on micromagnetic simulations, we attribute to nonlinear microwave excitations. Our result provides a new pathway for detecting pure spin currents that originate from many spintronics phenomena, such as spin Hall and spin Seebeck effects, and which can be applied to both metal and insulator spin current sources.
In this paper, we describe the optimization of transition-edge-sensor (TES) detector arrays for the third-generation camera for the South Pole Telescope. The camera, which contains ~16 000 detectors, ...will make high-angular-resolution maps of the temperature and polarization of the cosmic microwave background. Our key results are scatter in the transition temperature of Ti/Au TESs is reduced by fabricating the TESs on a thin Ti(5 nm)/Au(5 nm) buffer layer and the thermal conductivity of the legs that support our detector islands is dominated by the SiOx dielectric in the microstrip transmission lines that run along the legs.
We report a model that can be used to calculate superconducting transition temperature of a transition-edge sensor (TES), which is either a normal metal-superconductor-normal metal trilayer or a ...normal metal-superconductor bilayer. The model allows the T C estimation of a trilayer when the normal metals at the bottom and at the top are different. Furthermore, the model includes the spin flip time of the normal metals. We use the T C calculations from this model for selected Ir-based trilayers and bilayers to help understand potential designs of low T C TESs. A Au/Ir/Au trilayer can have a low T C because the superconducting order parameter is reduced with normal metals at both sides. On the other hand, an Ir/Pt bilayer can have a low T C because the much larger electron density of states of Pt reduces the superconducting order parameter more effectively. Moreover, the spin flip scattering of paramagnetic Pt also contributes to the T C reduction.
To control the angle between magnetizations in two adjacent ferromagnetic layers without using a rotator, a novel spin valve was designed and fabricated. A key element of the design is a replacement ...of a pinned ferromagnetic layer by a synthetic antiferromagnet (SAF). The predefined non-collinear magnetization configurations are produced by cooling the valve in different magnetic fields. Giant magnetoresistance (GMR) measurements allowed mapping of the angle between the magnetizations in the SAF and the free layer depending on the magnitude of the cooling field.
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