Spin extraction theory and its relevance to spintronics

Extraction of electrons from a semiconductor to a ferromagnet as well as the case of injection in the reverse direction may be formulated as a scattering theory. However, the presence of bound states at the interface arising out of doping on the semiconductor side must be taken into account in the scattering theory. Inclusion of the interface states yields an explanation of a recent result of spin imaging measurement which contradicts the current understanding of spin extraction. The importance of an extraction theory to spintronics is illustrated by an application to a spin switch.Comment: 4 two column pages, 3 figures, major revisions to improve the presentation. in addition, the new version includes an electrically controlled spin switc

Electric readout of magnetization dynamics in a ferromagnet-semiconductor system

We apply an analysis of time-dependent spin-polarized current in a semiconductor channel at room temperature to establish how the magnetization configuration and dynamics of three ferromagnetic terminals, two of them biased and third connected to a capacitor, affect the currents and voltages. In a steady state, the voltage on the capacitor is related to spin accumulation in the channel. When the magnetization of one of the terminals is rotated, a transient current is triggered. This effect can be used for electrical detection of magnetization reversal dynamics of an electrode or for dynamical readout of the alignment of two magnetic contacts.Comment: Revised version, 8 pages, 3 figure

Lateral diffusive spin transport in layered structures

A one dimensional theory of lateral spin-polarized transport is derived from the two dimensional flow in the vertical cross section of a stack of ferromagnetic and paramagnetic layers. This takes into account the influence of the lead on the lateral current underneath, in contrast to the conventional 1D modeling by the collinear configuration of lead/channel/lead. Our theory is convenient and appropriate for the current in plane configuration of an all-metallic spintronics structure as well as for the planar structure of a semiconductor with ferromagnetic contacts. For both systems we predict the optimal contact width for maximal magnetoresistance and propose an electrical measurement of the spin diffusion length for a wide range of materials.Comment: 4 pages, 3 figure

Spintronics for electrical measurement of light polarization

The helicity of a circularly polarized light beam may be determined by the spin direction of photo-excited electrons in a III-V semiconductor. We present a theoretical demonstration how the direction of the ensuing electron spin polarization may be determined by electrical means of two ferromagnet/semiconductor Schottky barriers. The proposed scheme allows for time-resolved detection of spin accumulation in small structures and may have a device application.Comment: Revised version, 8 two-column pages, 5 figures; Added: a comprehensive time dependent analysis, figures 3b-3c & 5, equations 6 & 13-16 and 3 references. submitted to Phys. Rev.

Spin and energy relaxation in germanium studied by spin-polarized direct-gap photoluminescence

Spin orientation of photoexcited carriers and their energy relaxation is investigated in bulk Ge by studying spin-polarized recombination across the direct band gap. The control over parameters such as doping and lattice temperature is shown to yield high polarization degree, namely larger than 40%, as well as a fine-tuning of the angular momentum of the emitted light with a complete reversal between right- and left-handed circular polarization. By combining the measurement of the optical polarization state of band-edge luminescence and Monte Carlo simulations of carrier dynamics, we show that these very rich and complex phenomena are the result of the electron thermalization and cooling in the multi-valley conduction band of Ge. The circular polarization of the direct-gap radiative recombination is indeed affected by energy relaxation of hot electrons via the X valleys and the Coulomb interaction with extrinsic carriers. Finally, thermal activation of unpolarized L valley electrons accounts for the luminescence depolarization in the high temperature regime

Penerapan Model Kooperatif Tipe Think Talk Write Untuk Meningkatkan Keterampilan Menulis Karangan Narasi Pada Siswa Sekolah Dasar

Penelitian ini bertujuan dapat meningkat keterampilan menulis karangan narasi pada mata pelajaran Bahasa Indonesia di kelas III Sekolah Dasar Negeri 015 Tandun melalui penerapan model kooperatif tipe Think Talk Write. Penelitian ini dilatar belakangi oleh rendahnya hasil keterampilan menulis karangan narasi yang tidak mencapai nilai KKM yang ditetapkan sekolah yaitu 75. Penelitian ini merupakan penelitian tindakan kelas. Subjek penelitian ini adalah siswa kelas III tahun ajaran 2018-2019 dengan jumlah siswa sebanyak 20 orang. Objek dalam penelitian ini adalah model pembelajaran kooperatif tipe Think Talk Write dan keterampilan menulis karangan narasi. Penelitian ini terdiri dari empat tahapan tiap siklus yaitu: perencanaa, pelaksanaan, pengamatan, dan refleksi. Penelitian ini dilakukan sebanyak 2 siklus yang masing-masing siklus terdiri dari dua kali pertemuan. Pengumpulan data dalam penelitian ini menggunakan dokumentasi dan tes. Berdasarkan hasil analisis data dapat diketahui bahwa terjadinya peningkatan keterampilan menulis karangan narasi pada mata pelajaran Bahasa Indonesia. Sebelum tindakan ketuntasan hasil keterampilan menulis karangan siswa hanya mencapai 25%, lalu pada siklus I pertemuan I meningkat menjadi 30%, siklus I pertemuan II meningkat menjadi 45% dan pada siklus II pertemuan I meningkat menjadi 70% kemudian siklus II pertemuan II meningkat lagi menjadi 85%. Dengan demikian dapat disimpulkan bahwa Penerapan Model Kooperatif Tipe Think Talk Write dapat Meningkatkan Keterampilan Menulis Karangan Narasi Pada Siswa Sekolah Dasar

Optical spin injection and spin lifetime in Ge heterostructures

We demonstrate optical orientation in Ge/SiGe quantum wells and study their spin properties. The ultrafast electron transfer from the center of the Brillouin zone to its edge allows us to achieve high spin-polarization efficiencies and to resolve the spin dynamics of holes and electrons. The circular polarization degree of the direct-gap photoluminescence exceeds the theoretical bulk limit, yielding ~37% and ~85% for transitions with heavy and light holes states, respectively. The spin lifetime of holes at the top of the valence band is found to be ~0.5 ps and it is governed by transitions between heavy and light hole states. Electrons at the bottom of the conduction band, on the other hand, have a spin lifetime that exceeds 5 ns below 150 K. Theoretical analysis of the electrons spin relaxation indicates that phonon-induced intervalley scattering dictates the spin lifetime.Comment: 5 pages, 3 figure

Graphite and graphene as perfect spin filters

Based upon the observations (i) that their in-plane lattice constants match almost perfectly and (ii) that their electronic structures overlap in reciprocal space for one spin direction only, we predict perfect spin filtering for interfaces between graphite and (111) fcc or (0001) hcp Ni or Co. The spin filtering is quite insensitive to roughness and disorder. The formation of a chemical bond between graphite and the open $d$-shell transition metals that might complicate or even prevent spin injection into a single graphene sheet can be simply prevented by dusting Ni or Co with one or a few monolayers of Cu while still preserving the ideal spin injection property

Design and evaluation of a subcutaneous contraceptive implant training simulator

ObjectiveTo design and fabricate a subcutaneous contraceptive implant insertion simulator, and to characterize the performance of nursing students trained with and without the simulator.MethodA cross‐sectional study was conducted on nursing students in Ghana who had no previous training in the insertion of contraceptive implants. They were given standardized training in insertion of implants from 25 April to 26 April, 2016, and then were randomly assigned to an intervention or control group. The control group watched insertions of live implants while the intervention group practiced using the simulator. Local materials were used to fabricate the simulator. The performance of both groups was assessed after the training.ResultsThe participants consisted of 50 nursing students. Those in the intervention group were more likely to: insert the implant accurately (95.2% vs 78.4%, P<0.001); take less time to complete an insertion (mean of 33.6 seconds vs 42.2 seconds, P<0.001); and commit fewer errors (1.9 vs 2.5, P=0.005) compared to the control group. In addition, participants rated the simulator high on 11/11 of the product requirements with the teaching (93.2%), learning (91.4%), and skill acquisition (88.6%) requirements being the highest rated.ConclusionA low‐cost, locally fabricated simulator is an effective tool for augmenting the current training protocol by improving insertion skills of contraceptive implants.Novices trained with the implant insertion simulator were able to perform error‐free simulated insertions more accurately and quickly compared with the current mode of training.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151337/1/ijgo12896_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151337/2/ijgo12896.pd