Investigation of Spin-Dependent Transport Properties and Spin–Spin Interactions in a Copper-Phthalocyanine–Cobalt Nanocomposite System

Abstract

We have fabricated a series of copper-phthalocyanine–cobalt (CuPc–Co) nanocomposites (compositional ratio of CuPc:Co=4:1), wherein Co nanoparticles were embedded within a CuPc matrix, in order to study the spin transport properties and to investigate spin–spin interactions between conducting spins and localized spins in the CuPc. Nonlinear characteristics of electric current, I–V (2N-1), (V: bias voltage, N: order of co-tunneling) were observed, where the fifth order co-tunneling was clarified. The order of the co-tunneling effect in CuPc–Co was almost equal to that in a rubrene–Co nanocomposite with almost the same diameter of the Co nanoparticles. We have not found clear evidence of spin-flip processes, as observed in other molecular systems, which may be attributed to the spin-coupling between localized spins in the CuPc and spins in Co.

Spin-pump-induced spin transport in a thermally-evaporated pigment-red film

“…Carbon-based molecular materials for the wide possibility of spintronic applications have attracted much attention [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Those are expected as good spin transport materials originating from the weak spin-orbit interaction in the materials.…”

“…In the conventional -conjugated molecular electronics, a copper-phthalocyanine (CuPc) molecular film [14][15][16][17] and a perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecular film [17][18][19] are usually used to overcome the above physical durability problem. The CuPc and the PTCDA are respectively called as a pigment-blue and a pigment-red, which are robust materials due to the rigid molecular frames.…”

Molecular spintronics

“…Here, it is noteworthy that spin transport even in a short organic spin channel using rubrene, Alq3 and CuPc (<10 nm) is often tunneling spin transport (for example, see Fig. 23) [69][70][71][72][73] and tunneling spin transport can be realized via ferromagnetic particles which were unintentionally formed in organic spacers [74], and also that Jiang et al reported the absence of the spin transport in the case of hole injection in Alq3 sandwiched by Co and LSMO [75]. On the other hand, Fahlman and Dediu carried out careful studies on an investigation of a band alignment of Co/Alq3/LSMO by introducing photoemission spectroscopy (Fig.…”

Modulating the Magnetic Coupling in Paramagnetic Co Nanoparticles Embedded in Tris(8-hydroxyquinoline)aluminum for Spintronics Applications

“…The investigation of coevaporation of cobalt and OSC, such as C 60 fullerenes, rubrene, copper phthalocyanine (CuPc), and Alq 3 , has been reported − because the ferromagnetic cobalt is reactive and serves as an electron donor to hybridize with OSC. Moreover, nanometallic Co clusters have been reported to show a superparamagnetic property and to express a phase transition from ferromagnetic to superparamagnetic when the size decreases to several nanometers. − Nanoclusters have thus great potential applications in nanoscale bits of novel electronics or drug delivery of diagnostic tools or therapeutic agents. − In this work we fabricated by coevaporation paramagnetic Alq 3 –Co thin films where the Co nanoclusters were embedded in Alq 3 in a series with varied volume ratios of Alq 3 to Co as shown in Figure a.…”