Search query: Spin injection/detection using an organic-based magnetic semiconductor

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abstract: The new paradigm of electronics, 'spintronics' promises to extend the functionality of information storage and processing in conventional electronics. The principal spintronics device, the 'spin valve' consists of two magnetic layers decoupled by a spin transporting spacer, which allows parallel (on) and antiparallel (off) alignment of the magnetizations (spins) of the two magnetic layers. The device resistance then depends on the spin alignment controlled by the external magnetic field. In pursuit of semiconductor spintronics, there have been intensive efforts devoted to develop room temperature magnetic semiconductors and also to incorporate both inorganic semiconductors and carbon based materials as the spin transporting channels. Molecule/organic based magnets, which allow chemical tuning of electronic and magnetic properties, are a promising new class of magnetic materials for future spintronic applications. Here, we report the realization of an organic based magnet as an electron spin polarizer in the standard spintronics device geometry. A thin non magnetic organic semiconductor layer and an epitaxial ferromagnetic oxide film were employed to form a hybrid magnetic tunnel junction. The results demonstrate the spin polarizing nature of the organic based magnetic semiconductor, vanadium(TCNE: tetracyanoethylene)(x) (x approximately 2; T(c) approximately 400 K) and its function as a spin injector/detector in hybrid magnetic multilayer devices.
author_names: Jung-Woo Yoo

Chia-Yi Chen

Ho Won Jang

Chung Wung Bark

Vladimir N Prigodin

C B Eom

Arthur J Epstein
title: Spin injection/detection using an organic based magnetic semiconductor.
venue: Nature materials
year: 2010

abstract: Nature Materials 9, 638 642 (2010) published online: 18 July 2010; corrected after print: 23 July 2010. In the original version of this article published online and in print, the received date should have been 29 December 2009, not 2010. This has been corrected in the PDF and HTML versions of this Letter.
author_names: Jung-Woo Yoo

Chia-Yi Chen

Ho Won Jang

Chung Wung Bark

Vladimir N Prigodin

C B Eom

Arthur J Epstein
title: Erratum: Spin injection/detection using an organic based magnetic semiconductor
year: 2010

abstract: Ferromagnetic semiconductors with structural flexibility are an indispensable feature for future flexible spin electronic applications. In this case, we introduce magnetic ingredients into an organic semiconductor, namely, pentacene, to form a ferromagnetic organic semiconductor (FOS) The first observation for ferromagnetic Ni doped pentacene semiconductors at room temperature in the field of semiconductor spintronics is reported in this article. To date, the mechanism of FOSs with ferromagnetism is not understood yet, especially when their Curie temperature is enhanced above room temperature. Here, we demonstrate dopants of Ni atoms and the modulation of the growth temperature in the FOS films to achieve room temperature ferromagnetic properties in a series of FOS films, one of which has a maximum coercivity of 257.6 Oe. The spin exchange interaction between a Ni atom and a pentacene molecule is detected through the magnetic hysteresis obtained using a superconducting quantum interference device magnetometer. We verify the effectiveness of this spin coupling through magnetic force microscopy, Raman spectroscopy, scanning Kelvin probe microscopy, and theoretical simulation. A model for the indirect spin coupling between Ni atoms is proposed for the mechanism of room temperature ferromagnetic ordering of spins due to the exchange force indirectly. We believe that the p electrons of pentacene molecules at the triple state for this model can support the spin coupling of electrons of Ni atoms. Our findings facilitate the development of brand new spintronic devices with structural flexibility and room temperature ferromagnetism.
author_names: Wei-Yang Chou

Sheng-Kuang Peng

Fu-Hsuan Chang

Jr-Jeng Ruan

Tsung Yeh Ho
title: Ferromagnetism above Room Temperature in a Ni Doped Organic Based Magnetic Semiconductor.
venue: ACS applied materials interfaces
year: 2021

abstract: summary, we have successfully produced highly ordered arrays of single crystalline antimony nanowires with diameters of 40 nm in porous anodic alumina membranes by pulsed electrodeposition. The results of XRD and HRTEM indicate that the nanowires have a uniform hexagonal antimony single crystalline structure and grow along the [112 A 0] direction. The resistance at zero magnetic field demonstrates that single crystalline antimony nanowires with diameters of 40 nm remain metallic in character. It would be very interesting to produce a metal+ semiconductor nanowire heterogeneous junction array consisting of antimony metal and bismuth semiconductor. Further work is under way. Experimental The AAM was prepared as follows: high purity (99.999 aluminum was electropolished at 23 V in a mixture solution of 70 perchloric acid and etha nol (1:9) at 4 C for 2 min. Anodization was carried out at 40 V DC in 0.25 M aqueous oxalic acid electrolyte at 7 C. After the anodization, the central sub strate was removed in a saturated SnCl 4 solution, and the surrounding aluminum was retained as a support. Then the barrier was dissolved in 6 wt. phos phoric acid solution at 30 C for 60 min. Finally, a layer of Au was sputtered onto one side of the AAM to serve as the working electrode. Field emission microscopy observations indicate that the AAM is an almost perfect hexagonally arranged nanochannel array with a channel diameter of 40 nm. The antimony plating solution consisted of 0.02 The antimony nanowire arrays were observed using a field emission microscope (JEOL JSM 6700F) and a transmission electron microscope (JEOL 200CX and JEL 2010) For TEM analysis, the specimens were prepared by dissolving the AAMs with 5 wt. NaOH solution, dispersing the antimony nano wires in ethanol by ultrasonic vibration, and then placing drops of the dispersion on carbon films on a copper grid. The FEM specimen was obtained by dissolving the upper part of the AAM with 5 wt. NaOH solution. The X ray diffraction spectrum was obtained using a rotating anode X ray diffractometer (D/MAX rA) with Cu Ka radiation (k 1.542 The electrical resistance was measured by the standard DC four probe method in the temperature range from 20 K to 273 K. In the past decade there has been extensive progress in using the spin property of electrons in inorganic multilayers as a means of introducing revolutionary new types of electronics (e.g. spin valves, spin light emitting diodes) termed spin tronics. [1] Challenges including improved
author_names: Vladimir N Prigodin

N P Raju

Konstantin Pokhodnya

Joel S Miller

Arthur J Epstein
title: Spin Driven Resistance in Organic Based Magnetic Semiconductor V[TCNE]x
year: 2002

abstract: Organic based magnets are intriguing materials with unique magnetic and electronic properties that can be tailored by chemical methodology. By using molecular layer deposition (MLD) we demonstrate the thin film fabrication of V[TCNE: tetracyanoethylene](x) of the first known room temperature organic based magnet. The resulting films exhibit improvement in surface morphology, larger coercivity (80 Oe) and higher Curie temperature/thermal stability (up to 400 K) Recently, the MLD method has been widely studied to implement fine control of organic film growth for various applications. This work broadens its application to magnetic and charge transfer materials and opens new opportunities for metal organic hybrid material development and their applications in various multilayer film device structures. Finally, we demonstrate the applicability of the multilayer V[TCNE](x) as a spin injector combining LSMO, an standard inorganic magnetic semiconductor, for spintronics applications.
author_names: Chi-yueh Kao

Jung-Woo Yoo

Yong Min

Arthur J Epstein
title: Molecular layer deposition of an organic based magnetic semiconducting laminate.
venue: ACS applied materials interfaces
year: 2012

abstract: Over the last two decades organic spintronics has developed into a striving field with exciting reports of long spin diffusion lengths and spin relaxation times in organic semiconductors (OSCs) Easily processed and inexpensive, OSCs are considered a potential alternative to inorganic materials for use in spintronic applications. Spin currents have been detected in a wide range of materials, however, there is still uncertainty over the origin of the signals. Recently, we explored spin transport through an organic semiconductor with lateral spin injection and detection architectures, where the injected spin current is detected non locally via spin to charge conversion in an inorganic detector. In this work we show that the widely used control experiments like linear power dependence and inversion of the signal with the magnetic field are not sufficient evidence of spin transport and can lead to an incorrect interpretation of the signal. Here, we use in plane angular dependent measurements to separate pure spin signal from parasitic effects arising from spin rectification (SREs) Apart from well established anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE) we observed a novel effect which we call spurious inverse spin Hall effect (ISHE) It strongly resembles ISHE behaviour, but arises in the ferromagnet rather than the detector meaning this additional effect has to be considered in future work.
author_names: Piotr Skalski

Olga Zadvorna

Deepak Venkateshvaran

Henning Sirringhaus
title: Distinguishing spin pumping from spin rectification in organic semiconductor based lateral spin pumping device architectures
year: 2021

abstract: Abstract The future of spin electronics or "spintronics" lies in the development of viable magnetic semiconductors that can effectively operate at room temperature Vanadium tetracyanoethylene (V[TCNE]~2) is a magnetic semiconductor with an ordering temperature well above that of room. Its highly disordered structure has hampered a comprehensive description of the interactions between the V and TCNE sublattices that give rise to its magnetic and electrical properties. We report the results of high resolution x ray absorption (XAS) and magnetic circular dichrosim (MCD) studies probing the electronic structure of V[TCNE]~2 in an effort to elucidate the nature of these interactions. Included in this study are the first reports of gas phase neutral TCNE XAS spectra as well as the first reports of MCD spectra of the carbon and nitrogen absorption edges for the V[TCNE]~2 system. The vanadium spectrum reveals a spin split L3 and L2 spectrum that is qualitatively modeled for V(II) using crystal field multiplet (CFM) theory calculations except for a region of excess intensity on the high energy side of both the L3 and L2 absorption edges. We speculate that the origin of this excess intensity is vanadium present in valence states higher than V(II) and antibonding states from the hybridization of the V centers and TCNE. Despite the localized nature of the x ray absorption process the C and N spectra of the TCNE suggest that we are probing molecular final states of TCNE from different sites rather atomically isolated states. In addition, the carbon and nitrogen absorption spectra reveal that this molecular orbital structure remains largely intact in going from the gas phase to the condensed phase in V[TCNE]~2.
author_names: Derek M Lincoln
title: The electronic structure and field effects of an organic based room temperature magnetic semiconductor
year: 2007

abstract: Tailoring molecular spinterface between novel magnetic materials and organic semiconductors offers promise to achieve high spin injection efficiency. Yet it has been challenging to achieve simultaneously a high and nonvolatile control of magnetoresistance effect in organic spintronic devices. To date, the largest magnetoresistance ~300% at T 10 K) has been reached in tris (8 hydroxyquinoline) aluminum (Alq3) based organic spin valves (OSVs) using La0.67Sr0.33MnO3 as a magnetic electrode. Here we demonstrate that one type of perovskite manganites, i.e. a (La2/3Pr1/3)5/8Ca3/8MnO3 thin film with pronounced electronic phase separation (EPS) can be used in Alq3 based OSVs to achieve a large magnetoresistance (MR) up to 440% at T 10 K and a typical electrical Hanle effect as the Hallmark of the spin injection. The contactless magnetic field controlled EPS enables us to achieve a nonvolatile tunable MR response persisting up to 120 K. Our study suggests a new route to design high performance multifunctional OSV devices using electronic phase separated manganites. Organic materials hold great potential of for spintronic applications. Here the authors show electronic phase dependent magnetoresistance (MR) effect in LPCMO/Alq3/Co junctions with large MR up to 440% at 10 K as well as electrical Hanle effect as the Hallmark of the spin injection.
author_names: Wenting Yang

Qian Shi

Tian Miao

Qiang Li

Peng Cai

Hao Liu

Hanxuan Lin

Yu Bai

Yinyan Zhu

Yang Yu

Lina Deng

Wenbin Wang

Lifeng Yin

Dali Sun

X-G Zhang

Jian Shen
title: Achieving large and nonvolatile tunable magnetoresistance in organic spin valves using electronic phase separated manganites
venue: Nature Communications
year: 2019

abstract: Figure 1 a) Device structure and b) schematic view of the energy levels of V[TCNE] x x 2) Spintronics is the new paradigm of electronics and utilizes the spin degree of freedom of the electron. 1 In addition to metalbased spintronic devices, which already have wide applications (e.g. read heads of hard disk drives) semiconductor spintronics provides the possibility to combine logic, communication, and storage operation using hybrid devices. 2 Recently, spintronic devices based on organic materials have attracted much attention because of the potential long spin lifetime due to low spin orbit coupling and weak hyperfi ne interaction, as well as the ability to fabricate low cost, light weight, and mechanically fl exible devices. 3 9 Organic semiconductors have been used as the spacers in spin valve devices with ferromagnetic metal or transitional metal oxide contacts. One fundamental obstacle for spin injection from a ferromagnetic metal into a semiconductor is the conductivity mismatch. 10 The development of fully spinpolarized magnetic semiconductors offers a promising route to circumvent this problem. Organic based magnets such as V[TCNE] x x 2, TCNE: tetracyanoethylene) provide advantages including high magnetic ordering temperature, fully spin polarized semiconducting electronic structure, chemical tunability, and low temperature processing. 11 Here, we show results for spin injection and detection in an all organic based spin valve using the organic magnetic semiconductor V[TCNE] x as both the spin injector and analyzer. We observed unusual inverted spin valve effect and propose that the negative magnetoresistance (MR) originates from the spin dependent tunneling between highly spin polarized bands split by Coulomb interaction. V[TCNE] x is the fi rst reported room temperature moleculebased magnet with magnetic ordering temperature T C 400 K. 12 The magnetic order originates from the antiferromagnetic coupling between the three unpaired electrons of the V 2
author_names: Bin Li

Chi-yueh Kao

Jung-Woo Yoo

Vladimir N Prigodin

Arthur J Epstein
title: Magnetoresistance in an all organic based spin valve.
venue: Advanced materials
year: 2011

abstract: The ferromagnetic electrode on which a clean high quality electrode/interlayer interface is formed, is critical to achieve efficient injection of spin dependent electrons in spintronic devices. In this work, we report on the preparation of graphene passivated cobalt electrodes for application in vertical spin valves (SVs) In this strategy, high quality monolayer and bi layer graphene sheets have been grown directly on the crystal Co film substrates in a controllable process by chemical vapor deposition. The electrode is oxidation resistant and ensures a clean crystalline graphene/Co interface. The AlO x based magnetic junction devices using such bottom electrodes, exhibit a negative tunnel magneto resistance (TMR) of ca. 1.0% in the range of 5 K 300 K. Furthermore, we have also fabricated organic based SVs employing a thin layer of fullerene C60 or an N type polymeric semiconductor as the interlayer. The devices of both materials show a tunneling behavior of spin polarized electron transport as well as appreciable TMR effect, demonstrating the high potential of such graphene coated Co electrodes for organic based spintronics.
author_names: Guoqing Zhou

Guoqiang Tang

Tian Li

Guoxing Pan

Zanhong Deng

Fapei Zhang
title: Graphene passivated cobalt as a spin polarized electrode: growth and application to organic spintronics
year: 2017