Tunneling anisotropic magnetoresistance in organic spin valves

Grünewald, M.; Wahler, M.; Schumann, Florian; Michelfeit, M.; Gould, C.; Schmidt, R.; Würthner, Frank; Schmidt, G.; Molenkamp, L. W.

doi:10.1103/physrevb.84.125208

Cited by 60 publications

(57 citation statements)

References 26 publications

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“…S7). The larger MRmax observed for the LSMO-based OSV-like device indicates that spin aligned carrier injection indeed occurs into the OSEC interlayer, consistent with the different abilities of NiFe and LSMO FM electrodes to inject spin aligned carriers into an OSEC (40% and higher MR have been reported when using LSMObased conventional OSV [4][5][6][7][8][9][10][11][12], whereas 0.1 to 0.3% MR have been reached when using NiFe- response does not originate from 'tunneling anisotropy magnetoresistance' (TAMR) [38], in which the switching field is determined by the anisotropy magnetization of the bottom FM electrode, and…”

Section: A Magnetoresistance Measurementssupporting

confidence: 54%

Spintronic detection of interfacial magnetic switching in a paramagnetic thin film of tris(8-hydroxyquinoline)iron(III)

et al. 2017

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Organic semiconductors find increasing importance in spin transport devices due to the modulation and control of their properties through chemical synthetic versatility. The organic materials are used as interlayers between two ferromagnet (FM) electrodes in organic spin valves (OSV), as well as for magnetic spin manipulation of metal-organic complexes at the molecular level. In the latter, specifically, the substrate-induced magnetic switching in a paramagnetic molecule has been evoked extensively, but studied by delicate surface spectroscopies. Here we present evidence of the substantial magnetic switching in a nanosized thin film of the paramagnetic molecule, tris(8-hydroxyquinoline)iron(III) (Feq3) deposited on a FM substrate, using the magnetoresistance response of electrical 'spin-injection' in an OSV structure; and the inverse-spin-Hall effect induced by state-of-art pulsed microwave 'spin-pumping'. We show that interfacial spin control at the molecular level may lead to a macroscopic organic spin transport device; thus, bridging the gap between organic spintronics and molecular spintronics.

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Section: A Magnetoresistance Measurementssupporting

confidence: 54%

Spintronic detection of interfacial magnetic switching in a paramagnetic thin film of tris(8-hydroxyquinoline)iron(III)

et al. 2017

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“…The magnetoresistance in such tunnel devices is referred to as tunnelling anisotropy magnetoresistance (TAMR), which arises from the magnetization-dependent total density of states of the tunnelling electrons at the surface. The observation of TAMR has also been reported in organic spin-valve structures using epitaxial lanthanum strontium manganese oxide electrodes 23 . However, our above experimental observations suggest the origin of IMR in our device to be interfacial and different to that of TAMR.…”

mentioning

confidence: 56%

Interface-engineered templates for molecular spin memory devices

Raman

Kamerbeek

Mukherjee

et al. 2013

Nature

426

409

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The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices 1, 2 , opening avenues for developing multifunctional molecular spintronics 3 . Such ideas have been researched extensively, using singlemolecule magnets 4, 5 and molecules with a metal ion 6 or nitrogen vacancy 7 as localized spin-carrying centres for storage and for realizing logic operations 8 . However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task 9 . In this regard, delocalized carbon-based radical species with unpaired spin, such as phenalenyl 10 , have shown promise. These phenalenyl moieties, which can be regarded as graphene fragments, are formed by the fusion of three benzene rings and belong to the class of open-shell systems. The spin structure of these molecules responds to external stimuli 11, 12 (such as light, and electric and magnetic fields), which provides novel schemes for performing spin memory and logic operations. Here we construct a molecular device using such molecules as templates to engineer interfacial spin transfer resulting from hybridization and magnetic exchange interaction with the surface of a ferromagnet; the device shows an unexpected interfacial magnetoresistance of more than 20 per cent near room temperature. Moreover, we successfully demonstrate the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. Owing to strong magnetic coupling with the ferromagnet, such independent switching of an adsorbed magnetic molecule has been unsuccessful with single-molecule magnets 13 . Our findings suggest the use of chemically amenable phenalenyl-based molecules as a viable and scalable platform for building molecular-scale quantum spin memory and processors for technological development.The diversity and flexibility of molecular synthesis has given researchers ample freedom to design functional molecules for spintronics. These include molecular magnets 14 , spinfilter molecules 15 , spin-crossover molecules 16 , molecular batteries 17 , molecular conductors 10 , molecular switches 12 , and spacer layers for organic spin valves 18 and magnetic tunnel junctions 19,20 . Using such synthetic techniques, we have designed a neutral planar phenalenyl-based molecule, zinc methyl phenalenyl (ZMP, C 14 H 10 O 2 Zn; see Fig. 1a and Methods), that has no net spin. When these molecules are grown on a ferromagnetic surface, interface spin transfer causes a hybridized organometallic supramolecular magnetic layer to develop, which shows a large magnetic anisotropy and spin-filter properties 21 . This interface layer creates a spin-dependent resistance and gives rise to an interface magnetoresistance (IMR) effect.

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“…[1][2][3][4][5][6][7][8]. In many cases it is still unclear whether a tunneling based magnetoresistance effect (TMR/TAMR) 6,8,9 or actual spin injection and consequently giant magnetoresistance (GMR) 2,7 is the origin of the observed effects. Although the investigation of I/V-characteristics or the temperature dependence of the device resistance can give indications about the underlying transport mechanisms, final proof is still missing.…”

Section: Introductionmentioning

confidence: 99%

“…Although the investigation of I/V-characteristics or the temperature dependence of the device resistance can give indications about the underlying transport mechanisms, final proof is still missing. Further complications arise from the facts that charge injection into organic semiconductors is often based on tunneling 10 and that intermixing of spin dependent transport and tunneling anisotropic magnetoresistance 9 can prevent a clear distinction between TMR and GMR.…”

Section: Introductionmentioning

confidence: 99%

Vertical organic spin valves in perpendicular magnetic fields

et al. 2013

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We report the results of magnetoresistance measurements in vertical organic spin valves with the magnetic field oriented perpendicular to the layer stack. The magnetoresistance measurements were performed after carefully preparing either parallel or antiparallel in-plane magnetization states of the magnetic electrodes in order to observe traces of Hanle precession. Due to the low mobility in organic semiconductors the transit time of spin polarized carriers should allow for precession of the spins in perpendicular fields which in statistical average would quench the magnetoresistance.However, in none of the experiments we do observe any change in resistance while sweeping the perpendicular field, up to the point where the electrode's magnetization starts to reorient. This absence of Hanle type effects indicates that the magnetoresistance is not based on the injection of spin polarized electrons into the organic semiconductor but rather on tunneling through pinholes superimposed with tunneling anisotropic magnetoresistance.

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Tunneling anisotropic magnetoresistance in organic spin valves

Cited by 60 publications

References 26 publications

Spintronic detection of interfacial magnetic switching in a paramagnetic thin film of tris(8-hydroxyquinoline)iron(III)

Spintronic detection of interfacial magnetic switching in a paramagnetic thin film of tris(8-hydroxyquinoline)iron(III)

Interface-engineered templates for molecular spin memory devices

Vertical organic spin valves in perpendicular magnetic fields

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