The energy bandgap of an insulator is large enough to prevent electron excitation and electrical conduction. But in addition to charge, an electron also has spin, and the collective motion of spin ...can propagate-and so transfer a signal-in some insulators. This motion is called a spin wave and is usually excited using magnetic fields. Here we show that a spin wave in an insulator can be generated and detected using spin-Hall effects, which enable the direct conversion of an electric signal into a spin wave, and its subsequent transmission through (and recovery from) an insulator over macroscopic distances. First, we show evidence for the transfer of spin angular momentum between an insulator magnet Y(3)Fe(5)O(12) and a platinum film. This transfer allows direct conversion of an electric current in the platinum film to a spin wave in the Y(3)Fe(5)O(12) via spin-Hall effects. Second, making use of the transfer in a Pt/Y(3)Fe(5)O(12)/Pt system, we demonstrate that an electric current in one metal film induces voltage in the other, far distant, metal film. Specifically, the applied electric current is converted into spin angular momentum owing to the spin-Hall effect in the first platinum film; the angular momentum is then carried by a spin wave in the insulating Y(3)Fe(5)O(12) layer; at the distant platinum film, the spin angular momentum of the spin wave is converted back to an electric voltage. This effect can be switched on and off using a magnetic field. Weak spin damping in Y(3)Fe(5)O(12) is responsible for its transparency for the transmission of spin angular momentum. This hybrid electrical transmission method potentially offers a means of innovative signal delivery in electrical circuits and devices.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We investigated anomalous Ettingshausen effect (AEE) and anomalous Nernst effect (ANE) for the same device consisting of an FePt thin film. The temperature modulation due to the AEE was visualized ...using the active infrared emission microscopy, called lock-in thermography. On the other hand, the ANE voltage was detected under the temperature gradient induced by the heater built into the device. We experimentally evaluated the magnitudes of AEE and ANE, taking into account the heat loss to the substrate, and discussed the relationship between AEE and ANE.
Spin caloritronics, a research field studying on the interconversion between a charge current (Jc) and a heat current (Jq) mediated by a spin current (Js) and/or magnetization (
), has attracted much ...attention not only for academic interest but also for practical applications. Newly discovered spin-caloritronic phenomena such as the spin Seebeck effect (SSE) have stimulated the renewed interest in the thermoelectric phenomena of a magnet, which have been known for a long time, e.g. the anomalous Nernst effect (ANE). These spin-caloritronic phenomena involving the SSE and the ANE have provided with a new direction for thermoelectric conversion exploitingJsand/or
. Importantly, the symmetry of ANE allows the thermoelectric conversion in the transverse configuration betweenJqandJc. Although the transverse configuration is totally different from the conventional longitudinal configuration based on the Seebeck effect and has many advantages, we are still facing several issues that need to be solved before developing practical applications. The primal issue is the improvement of conversion efficiency. In the case of ANE-based applications, a material with a large anomalous Nernst coefficient (SANE) is the key for solving the issue. This review article introduces the increase ofSANEcan be achieved by forming superlattice structures, which has been demonstrated for several kinds of materials combinations. The overall picture of studies on spin caloritronics is first surveyed. Then, we mention the pioneering work on the transverse thermoelectric conversion in superlattice structures, which was performed using Fe-based metallic superlattices, and show the recent studies for the Ni-based metallic superlattices and the ordered alloy-based metallic superlattices.
This paper reports the systematic investigation of vortex-type spin torque oscillation in circular disks of highly spin-polarized Co2Fe0.4Mn0.6Si (CFMS) Heusler alloys. We fabricated the ...current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with various disk diameters (D) using the layer stack of CFMS/Ag3Mg/CFMS. The gyrotropic motion of the vortex core was successfully excited for the CFMS circular disks with 0.2 µm D 0.3 µm. The CPP-GMR device with D = 0.2 µm exhibited the Q factor of more than 5000 and the large output power of 0.4 nW owing to the high coherency of vortex dynamics and the high spin-polarization of CFMS. However, the Q factor was remarkably decreased as D was reduced from 0.2 µm to 0.14 µm. The comparison with the calculated resonance frequencies suggested that this degradation of the Q factor was due to the transition of the oscillation mode from the vortex mode to other modes such as the low-coherent out-of-plane precession mode. The present experimental results also suggest that there exists an adequate disk size for the enhanced Q factor of the vortex-type spin torque oscillation.
The perpendicular magnetocrystalline anisotropy, magnetoelastic properties as well as the Gilbert damping factor in Co2Fe0.4Mn0.6Si thin films were found to depend on a magnetic layer thickness, and ...they can be also tuned by the application of additional Ag buffer layer. The tetragonal distortion of a magnetic layer was found to increase with decreasing thickness, and after the application of an additional Ag buffer layer, the character of this distortion was changed from tensile to compressive in the plane of a film. A correlation between the tetragonal distortion and perpendicular magnetocrystalline anisotropy was found. However, the magnitude of the observed tetragonal distortion for most samples seems to be too small to explain alone the experimentally found large magnitude of the perpendicular magnetocrystalline anisotropy. For these samples, other mechanisms including both surface and volume effects must be taken into account.
Abstract
Co
2
Fe
0.4
Mn
0.6
Si (CFMS) and Co
2
FeGa
0.5
Ge
0.5
(CFGG) Heusler alloys are among the most promising thin film materials for spintronic devices due to a high spin polarization, low ...magnetic damping and giant/tunneling magnetoresistance ratios. Despite numerous investigations of Heusler alloys magnetic properties performed up to now, magnetoelastic effects in these materials remain not fully understood; due to quite rare studies of correlations between magnetoelastic and other magnetic properties, such as magnetic dissipation or magnetic anisotropy. In this research we have investigated epitaxial CFMS and CFGG Heusler alloys thin films of thickness in the range of 15–50 nm. We have determined the magnetoelastic tensor components and magnetic damping parameters as a function of the magnetic layer thickness. Magnetic damping measurements revealed the existence of non-Gilbert dissipation related contributions, including two-magnon scattering and spin pumping phenomena. Magnetoelastic constant B
11
values and the effective magnetic damping parameter α
eff
values were found to be in the range of − 6 to 30 × 10
6
erg/cm
3
and between 1 and 12 × 10
–3
, respectively. The values of saturation magnetostriction λ
S
for CFMS Heusler alloy thin films were also obtained using the strain modulated ferromagnetic resonance technique. The correlation between α
eff
and B
11
, depending on magnetic layer thickness was determined based on the performed investigations of the above mentioned magnetic properties.
We have developed a new non-destructive sub-surface interfacial imaging technique. By controlling the penetration depth of the incident electrons, through control of the electron beam acceleration ...voltage in a scanning electron microscope, we can observe sub-surface interfaces. The voltages for imaging are selected based on Monte Carlo electron flight simulations, where the two voltages have >5% difference between the number of backscattered electrons generated in the layers above and below the buried interface under investigation. Due to the non-destructive nature, this imaging method can be used alongside an applied electrical current and voltage, allowing concurrent observations of the interfacial structures and transport properties, e.g. effective and active junction area, to occur. Magnetic tunnel junctions used in magnetic random access memory have been imaged and the data has been fed back to improve their fabrication processes. Our imaging method is therefore highly useful as both a quality assurance and development tool for magnetic memory and nanoelectronic devices.
We report an enhancement of the anomalous Nernst effect (ANE) in Ni/Pt (001) epitaxial superlattices. The transport and magnetothermoelectric properties were investigated for the Ni/Pt superlattices ...with various Ni layer thicknesses (t). The anomalous Nernst coefficient was increased up to more than 1 μ V K−1 for 2.0 nm ≤ t ≤ 4.0 nm , which was the remarkable enhancement compared to the bulk Ni. It has been found that the large transverse thermoelectric conductivity (αxy) , reaching αxy = 4.8 A K−1 m−1 for t = 4.0 nm , plays a prime role for the enhanced ANE of the Ni/Pt (001) superlattices.
PDF
