Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session R2: Advances in Collective Effects in Organic SemiconductorsInvited
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Sponsoring Units: DCMP GMAG Chair: Michael Flatte, University of Iowa Room: Ballroom II |
Thursday, March 17, 2016 8:00AM - 8:36AM |
R2.00001: Electrical detection of proton-spin motion in a polymer device at room temperature Invited Speaker: Christoph Boehme With the emergence of spintronics concepts based on organic semiconductors there has been renewed interest in the role of both, electron as well as nuclear spin states for the magneto-optoelectronic properties of these materials. In spite of decades of research on these molecular systems, there is still much need for an understanding of some of the fundamental properties of spin-controlled charge carrier transport and recombination processes [1]. This presentation focuses on mechanisms that allow proton spin states to influence electronic transition rates in organic semiconductors. Remarkably, even at low-magnetic field conditions and room temperature, nuclear spin states with energy splittings orders of magnitude below thermal energies are able to influence observables like magnetoresistance and fluorescence [2]. While proton spins couple to charge carrier spins via hyperfine interaction, there has been considerable debate about the nature of the electronic processes that are highly susceptible to these weak hyperfine fields. Here, experiments are presented which show how the magnetic resonant manipulation of electron and nuclear spin states in a $\pi$-conjugated polymer device causes changes of the device current [3]. The experiments confirm the extraordinary sensitivity of electronic transitions to very weak magnetic field changes and underscore the potential significance of spin-selection rules for highly sensitive absolute magnetic fields sensor concepts [4]. However, the relevance of these magnetic-field sensitive spin-dependent electron transitions is not just limited to semiconductor materials but also radical pair chemistry [5] and even avian magnetoreceptors [6]. [1] C. Boehme, J. M. Lupton, \textit{Nat. Nanotechn.} \textbf{8}, 9 (2013); [2] S.-Y. Lee et al., \textit{JACS} \textbf{133}, 072019 (2011); [3] H. Malissa et al., \textit{Science} \textbf{345}, 1487 (2014); [4] W. J. Baker et al., \textit{Nature Commun.} \textbf{3}, 898 (2012); [5] U.E. Steiner and T. Ulrich, \textit{Chem. Rev.} \textbf{89}, 51-147 (1989).; [6] T. Ritz, et al., \textit{Nature} \textbf{429}, 177–80 (2004). [Preview Abstract] |
Thursday, March 17, 2016 8:36AM - 9:12AM |
R2.00002: \textbf{Active control of magnetoresistance of organic spin valves using ferroelectricity} Invited Speaker: Jian Shen Organic spintronic devices have been appealing because of the long spin lifetime of the charge carriers in the organic materials and their low cost, flexibility and chemical diversity. In previous studies, the control of resistance of organic spin valves is generally achieved by the alignment of the magnetization directions of the two ferromagnetic electrodes, generating magnetoresistance. Here we employ a new knob to tune the resistance of organic spin valves by adding a thin ferroelectric interfacial layer between the ferromagnetic electrode and the organic spacer: the magnetoresistance of the spin valve depends strongly on the history of the bias voltage, which is correlated with the polarization of the ferroelectric layer; the magnetoresistance even changes sign when the electric polarization of the ferroelectric layer is reversed. These findings enable active control of resistance using both electric and magnetic fields, opening up possibility for multi-state organic spin valves. [Preview Abstract] |
Thursday, March 17, 2016 9:12AM - 9:48AM |
R2.00003: Organic magnetoelectroluminescence for room temperature transduction between magnetic and optical information Invited Speaker: Markus Wohlgenannt |
Thursday, March 17, 2016 9:48AM - 10:24AM |
R2.00004: New Directions for Organic Spintronics: Novel Materials and Emergent Phenomena Invited Speaker: Ezekiel Johnston-Halperin Organic and organic-based materials are attractive candidates for applications in magnetoelectronics and spintronics due to their low cost, ease of fabrication, and low spin-orbit coupling (and consequently long spin lifetimes). However, in comparison to the case for inorganic systems, robust intrinsic magnetic ordering in this class of materials is exceedingly rare and as a result the potential of these materials has yet to be fully realized. Here we present a series of recent breakthroughs in the synthesis, encapsulation, and measurement of organic-based magnets that lay the foundation for all organic magnetoelectronic and spintronic devices. We will discuss advances in encapsulation strategies that allow lifetimes of up to 1 month in air for functional magnetoelectronic devices, the use of ligand substitution to generate a library of related magnetic materials, the growth of all-organic and hybrid organic/inorganic magnetic heterostructures, and measurements of the magnetization dynamics that reveal ferromagnetic resonance (FMR) linewidths of \textasciitilde 1 G, comparable to or narrower than corresponding measurements in yttrium iron garnet (YIG). These results establish the validity of organic-based magnets for applications in next-generation magnetoelectronics and provide unique leverage on long-standing challenges in the field of organic spintronics. For example, organic magnetic heterostructures promise to provide an exciting opportunity to explore exchange, dynamic spin injection, and spin transport in all-organic spintronic devices. [Preview Abstract] |
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