Spin injection

Processes such as film extrusion, fiber spinning, injection molding, and drawing tend to impart orientation to products made from semicrystalline polymers. Mechanical, dielectric, and optical properties, to mention only three, are often strongly influenced by orientation. X-ray diffraction offers a direct approach to studying crystallite orientation because the Intensity that is diffracted into a detector placed at an appropriate position is directly proportional to the number of crystal lattice planes that are in the correct orientation for diffraction. The principles of such measurements are well described in textbooks 0,2). 

CH Li, G Kioseoglou, OMJ van t Erve, AT Hanbicki, BT Jonker, R Mallory, M Yasar, and A Petrou, Spin injection across (110) interfaces Fe/GaAs(110) spin-light-emitting diodes, Appl. Phys. Lett., 85 1544-1546, 2004. 

Fig. 18 Characteristics of Alq3 junctions with a CoFeB/MgO spin injection layer. The resistance switching curve is plotted as a function of applied field for different thicknesses or bias in the top panel, and the TMR ratio is plotted as function of bias, together with the d//dF curve for t = 0 and 2 nm in the bottom panel. The curve for t = 2 nm at 500 mV is included in the top panel. Taken from [23] with permission...

Barraud C, Seneor P, Mattana R, Stephane F, Bouzehouane K, Deranlot C, Graziosi P, Hueso L, Bergenti I, Dediu V, Petroff F, Fert A (2010) Unravelling the role of the interface for spin injection into organic semiconductors. Nat Phys 6 615-620... 

Rashba El (2000) Theory of electrical spin injection tunnel contacts as a solution of the conductivity mismatch problem. Phys Rev B 62 R16267-R16270... 

Fert A, Jaffres H (2001) Conditions for efficient spin injection from a ferromagnetic metal into a semiconductor. Phys Rev B 64 184420... 

Backfill the needle by using a sequencing gel loading tips to load the injectable. These tips fit inside the back of the needle, and the injectable will flow to the tip by capillary action. It is highly recommended to spin injectable before loading it, in order to remove any particles that could clog the needle. 

Injection of electron spins is preferable from the application point of view as electrons usually exhibit longer spin lifetime. Spin-injection experiments using n-type II-VI DMS in the magnetic field were performed by Fiederling et al. (1999) and Jonker et al. (2000). An appealing scheme for electrical electron spin injection from a ferromagnetic material... 

Fig. 36. (a) The structure of a light emitting diode for detection of electrical spin-injection, (b) Relative change in light polarization A P as a function of the magnetic held at four different temperatures. Inset compares the remanent magnetization as determined by SQUID magnetomery with the remanent A P (Ohno et al. 1999). 

As a result, nearly perfect interfaces between the ferromagnetic material and the semiconductor are not a prerequisite for efficient spin injection. It is for example possible to insert a non-magnetic seed layer between the ferromagnetic base layer and the semiconductor collector. Since hot electrons retain their spin moment while traversing the thin non-magnetic layer this will not drastically reduce the spin polarization of the injected current. Finally, since electron injection is ballistic in SVT and MTT devices the spin injection efficiency is not fundamentally limited by a substantial conductivity mismatch between metals and semiconductors [161, 162], The latter is the case in diffusive ferromagnetic metal/semiconductor contacts [163],... 

The second spin transistor design that is addressed uses a spin injecting current emitter, hence its acronym SPICE [167, 168], It uses semiconductors in its construction, like the SVT and MTT unlike them, however, its operation also requires spin-dependent transport in the semiconductor itself and thereby arise a small family of additional materials problems which are discussed below. 

Pending further work on these new magnetic semiconductors, metallic ferromagnets are in principle, the most convenient spin polarized sources for spin device work. The obvious configuration of direct Ohmic contact between metal and semiconductor proved to have fundamental shortcomings. The conductivity mismatch between the two materials implies very indifferent spin injection efficiency [174, 175], However it transpires that this difficulty is surmountable [176] by placing a tunnel barrier between the... 

Possible choices of semiconductor material for the SPICE design include gallium arsenide, silicon, and germanium. In the work described here, silicon was chosen as a reflection of its commercial importance, however this choice brings with it materials compatibility issues and surface chemistry complications. Silicon has a native oxide SiC>2 that is typically 2 nm thick which makes an inefficient spin injection tunnel barrier. 

In the present paper, we consider the results of the pump-probe investigation of the spin injection effects, leading to the non-magnetic material temporal magnetization. The approach used requires a time-resolved and surface-sensitive probe based on the SHG in pump-probe experiments, being intrinsically surface sensitive and consisting of contributions which are even and odd with respect to the magnetization reversal [2]. 

Important processing methods melt spinning, injection molding, extrusion... 

Schmidt, G. and L.W. Molenkamp, Electrical Spin Injection Spin-Polarized Transport from Magnetic into Non-Magnetic Semiconductors, in Semiconductor Spintronics and Quantum Computation, D.D. Awschalom, D. Loss, and N. Samarth, Editors. 2002, Springer Berlin, p. 93-106. 

The essential reason for the failure of spin injeetion from a ferromagnetic metal into a semieonduetor turned out to be the eonduetivity difference between these materials, whieh amounts to several orders of magnitude. It was shown that for the usual parameters of a ferromagnetie metal (i.e. (i) non-eomplete spin-polarisation at the Fermi-level, and (ii) spin-flip length 10 nm) the injeetion of spin-polarised electrons into a semiconductor is prohibited by fundamental laws of eleetrodynamics [6]. This impossibility of spin injection from a ferromagnetic metal into a semiconductor because of its conductance mismateh was derived eonsistently from models, based on electrochemical potential alignment or on a eireuit of parallel conductivity channels for spin-up and spin-down polarisation, respeetively [7]. 

In the last few years the first theoretical models describing spin injection at hybrid organic-inorganic interfaces and spin transport in organic materials were proposed. Most models take into account the polaronic nature of carriers in organic semiconductors [17, 18]. The interface role was strongly underlined by, among others. Smith and coworkers [19]. 

The present results show that the magnetic properties of ultrathin Fe films on ZnSe are quite different from those of bulk, in a completely similar way as in GaAs based interfaces. In particular, it is shown that spin injection into the semiconductor is possible only by using Fe films thicker than 8 ML. This will have strong impact on devices applications. 

The high orientability and the high shear-thinning behavior of liquid crystalline polymers provide a number of benefits in polymer processing, including the fiber spinning, injection molding, and fibrillation of TLCPs in... 

A number of difficulties have to be resolved to create successful devices. These include efficient spin injection into semiconductors and heterostructures, and a search for new spin-polarized materials. Other effects potentially important for spintronic devices include optical and electrical manipulation of ferromagnetism, current-induced switching and precessing of magnetization, and the possibility of a long coherence time for optically excited spins in semiconductors. For a good overview of the issues in spin electronics, including the prospects for spintronic quantum devices, see [3.118]. 

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