Magnetocurrent of Charge-Polarizable C₆₀-Diphenylaminofluorene Monoadduct-Derived Magnetic Nanocomposites

Abstract

We demonstrated the strategy of a nanocomposite design by the incorporation of both a delocalized π-electrons system in a closely bound acceptor-donor analogue chromophore, based on charge-polarizable C(60)(>DPAF-C(9)) nanostructure 1, and spin-polarized d-electrons in the form of γ-FeO(x) nanoparticles. Facile intramolecular electron transfer from the DPAF-C(9) donor moiety to the C(60) acceptor cage of 1 upon activation to the excited state with a long lifetime of the charge-separated state forms a possible mechanism to integrate semiconducting and magnetic properties in a single system. We observed an appreciable magnetocurrent (MC) of C(60)(>DPAF-C(9))-encapsulated magnetic γ-FeO(x) nanoparticles in PMMA matrix upon applying a magnetic field from 0 to 300 mT at either 77 K (12% MC) or 300 K (4.5% MC). Interestingly, the detailed analysis of magnetocurrent curve profiles taken at 77 K allowed us to conclude that the measured magnetocurrent may be attributed to the contributions from magnetic field-dependent excited-state populations in semiconducting structure (density-based MC), magnetism from magnetic structure (mobility-based MC), and product of density and mobility-based MC components (π-d electronic coupling). At the higher temperature region up to 300 K, the semiconducting mechanism dominated the determining factor of measured magnetocurrent. This experimental observation indicated the feasibility of combining delocalized π electrons and spin-polarized d electrons through charge transfer to induce internally coupled dual mobility- and density-based MC through the modulation of spin polarization and excited states in semiconducting/magnetic hybrid materials.

Microscopic theory of organic magnetoresistance based on kinetic equations for quantum spin correlations

“…where H 0 is a fitting parameter. The expression (39) was used to describe the lineshape of OMAR in a number of experimental works [6][7][8][9][10].…”

“…in organic solar cells [4]. These materials very often display an intriguing property that is called "organic magnetoresistance" or "OMAR" [5][6][7][8][9][10][11]. It is quite a strong magnetoresistance observed in magnetic fields 10 − 100gs both at low and room temperatures.…”

Investigating underlying mechanism in spectral narrowing phenomenon induced by microcavity in organic light emitting diodes

“…We know that polaron pairs can be largely formed towards light-emitting excitons in OLEDs under electrical injection 32, 33 . It has been experimentally observed that an external magnetic field can conveniently change the populations on the singlet and triplet polaron pairs, leading to magneto-EL 18, 34, 35 and magneto-current 36, 37 due to largely different recombination rates associated with singlets and triplets. Therefore, magneto-EL can be measured at two different conditions: constant-current and constant-voltage modes, while monitoring the EL intensity with scanning magnetic field 18, 19, 38 .…”

Photoexcitation-Controllable Magnetization in Magnetic–Semiconducting Nanohybrid Containing γ-Fe2O3–Graphene (0D–2D) van der Waals Heterostructure Based on Steady-State Pump–Probe Light Scattering Measurement in Magnetic Field

“…Therefore, a line shape narrowing phenomenon can provide an evidence that the magnetization becomes stronger under photoexcitation in the nanohybrid. Specifically, in the MYG nanohybrid, the graphene can interact with the γ-Fe 2 O 3 nanoparticles through d−π electron coupling , based on (i) long-range coulomb interactions and (ii) short-range spin–spin interactions between magnetic d electrons and semiconducting π electrons. , When the MYG nanohybrid is placed in excited state upon photoexcitation, both Coulomb interaction and spin–spin interaction between d electron in γ-Fe 2 O 3 nanoparticles and delocalized π electron in graphene can be enhanced. Consequently, stronger magnetization can be generated in γ-Fe 2 O 3 particles.…”