<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Δ</mml:mi><mml:mi>B</mml:mi></mml:mrow></mml:math>mechanism for fringe-field organic magnetoresistance

Cox, M Matthijs; Kersten, S. P.; Veerhoek, J M; Bobbert, PA Peter; Koopmans, B.

doi:10.1103/physrevb.91.165205

Cited by 7 publications

(11 citation statements)

References 22 publications

(42 reference statements)

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“…30 The second term gΔB is referred to as the ΔB mechanism, where ΔB is the difference of magnetic field at two adjacent sites, resulting in different spin precession rates causing the spin mixing between singlet states and triplet states. 18,40 Without MNPs, the spin mixing rate is proportional to ∆𝐵 = |∆𝑩 𝑵 |, where ∆𝑩 𝑵 is the nuclear field gradient (Fig. 6a).…”

Section: Resultsmentioning

confidence: 99%

“…Most recently, Wang et al 39 and Cox et al 40 have demonstrated a method of introducing a randomly localized magnetic field by using the magnetic fringe field of an additional ferromagnetic thin film positioned in the proximity of the OSEC film. Although the magnetic fringe field unambiguously interferes with the hyperfine field to distort the OMAR response, the line shape of the original OMAR response caused by HFI changes significantly.…”

Section: Introductionmentioning

confidence: 99%

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Magnetically tunable organic semiconductors with superparamagnetic nanoparticles

et al. 2019

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maximum 250 words) Magnetic nanoparticles (MNPs) exhibiting superparamagnetic properties might generate large magnetic dipole-dipole interaction with electron spins in organic semiconductors (OSECs). This concept could be considered analogous to the effect of hyperfine interaction (HFI). In order to investigate this model, Fe3O4 MNPs are used as a dopant for generating random hyperfine-like magnetic fields in a HFI-dominant π-conjugated polymer host, poly(2-methoxy-5-(2ethylhexyloxy)-1,4-phenylenevinylene) (MeH-PPV). The magnetoconductance (MC) response in organic light emitting diodes made by MeH-PPV/MNP blends is used to estimate the effective hyperfine field in the blends. Firstly, we find that the shape of the MC response essentially remains the same regardless of the MNP concentration, which is attributed to the similar functionality between the nuclear spins and magnetic moments of the MNPs. Secondly, the width of the MC response increases with increasing MNP concentration. Magneto-optical Kerr effect (MOKE) experiments and micromagnetic simulation indicate that the additional increase of the MC width is associated with the magnetization of the blend. Finally, the MC broadening has the same temperature dependent trend as the magnetization of the MNPs where the unique effect of the MNPs in their superparamagnetic and ferromagnetic regimes on the MC response is observed. Magneto-photoinduced absorption (MPA) spectroscopy confirms that the MC broadening is not due to defects introduced by the MNPs but a result of their unique superparamagnetic behavior. Our study yields a new pathway for tuning OSECs' magnetic functionality, which is essential for organic optoelectronic devices and magnetic sensor applications.Keywords: organic semiconductor, magnetic nanoparticle, magnetic field effect, hyperfine interaction, coherent spin mixing rate.Recently, there has been interest in coherent spin manipulation via controlling of the HFI by several state-of-the-art methods, including isotope exchange with different nuclear spins and pulsed electron-nuclear double resonance (ENDOR) spectroscopy. 13-15, 30, 35-38 The former method chemically replaces particular atoms in the molecule by atoms with different nuclear spins. [13][14][35][36][37] In conventional conducting polymers, the presence of new isotopes, e.g. 2 H and 13 C, significantly

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnetically tunable organic semiconductors with superparamagnetic nanoparticles

et al. 2019

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“…Thus, any explanation for the MR(B) response in the OSV-like device based on an intrinsic MR effect, such as organic MR (OMAR) [34] in the Feq3 layer, may be excluded. Other explanations such as B mechanism [35] can be also ruled out because of the absence of fringe field from the NiFe electrode, which exhibits uniform in-plane magnetization (confirmed by SQUID measurement below in Fig. 3a).…”

Section: A Magnetoresistance Measurementsmentioning

confidence: 99%

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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“…Engineered fringe field was first mentioned in MFE response of Alq 3 -based OLED having a structured FM electrode . Subsequently, magnetic fringe field control of the MFE response in OLEDs have been studied using different FM films. − Spatially inhomogeneous magnetic fringe field was believed to be responsible for these phenomena. Ref dubbed this mechanism as “Δ B mechanism”.…”

Section: Introductionmentioning

confidence: 99%

Magneto-Electroluminescence Study of Fringe Field in “Magnetic” Organic Light-Emitting Diodes

Liu

Chanana

Liu

et al. 2019

ACS Appl. Mater. Interfaces

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Magneto-electroluminescence (MEL) represents the electroluminescence intensity change upon application of an external magnetic field. We show that the MEL field response in "magnetic" organic light-emitting diodes, where one electrode is ferromagnetic (FM), is a powerful technique for measuring the induced fringe field, B ⃗ F , from the FM electrode in the organic layer. We found that the in-plane fringe field, B ⃗ F∥ , from 3 nm Co and Ni 80 Fe 20 FM electrodes is proportional to the applied field, B ⃗ ∥ . The fringe field of the 3 nm Ni 80 Fe 20 film was also investigated for an applied out-ofplane magnetic field, B ⃗ ⊥ . We found that the out-of-plane fringe field has two components: a component that is parallel or antiparallel to B ⃗ ⊥ and remains unchanged with the distance, d, from the FM electrode and the other component that is highly inhomogeneous, parallel to the surface, and steeply decreases with d. We show that the obtained B ⃗ F is independent of the underlying mechanism for the MEL(B) response and thus may be considered universal.

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ΔBmechanism for fringe-field organic magnetoresistance

Cited by 7 publications

References 22 publications

Magnetically tunable organic semiconductors with superparamagnetic nanoparticles

Magnetically tunable organic semiconductors with superparamagnetic nanoparticles

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

Magneto-Electroluminescence Study of Fringe Field in “Magnetic” Organic Light-Emitting Diodes

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