A Theoretical Study and Realization of New Spin Quantum Cross Structure Devices using Organic Materials
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1198-E07-01
A Theoretical Study and Realization of New Spin Quantum Cross Structure Devices using Organic Materials Kenji Kondo1, Hideo Kaiju1, 2, and Akira Ishibashi1 1 Laboratory of Quantum Electronics, Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020, Japan. 2 PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan. ABSTRACT We have proposed a spin quantum cross structure (SQCS) device as a candidate beyond CMOS. The SQCS device consists of two ferromagnetic metal thin films with their edges crossed, and sandwiches a few atoms or molecules. In this work, the spin dependent transport formula has been derived for SQCS devices with collinear ferromagnetic electrodes within the framework of the Anderson Hamiltonian. Also, the calculation of the magnetoresistance (MR) ratio has been done as a function of renormalized transfer matrices including magnetostriction effects and the other effects phenomenologically. It is shown that the MR ratio can be controlled by changing the renormalized coupling constants. The MR ratio is represented by a new formula. Also, we have realized an SQCS device with Ni magnetic thin-film electrodes, sandwiching poly (3-hexylthiophene) (P3HT): 6, 6-phenyl-C61-butyric acid methyl ester (PCBM) organic molecules between both the electrodes. The current-voltage characteristics of SQCS devices were measured by a four-terminal method and agree well with the theoretical results, quantitatively. INTRODUCTION Spintronic devices have attracted great interest from the viewpoint of new switching devices and new memory devices. Among these devices, a molecular spintronic device is one of many promising candidates since the discovery of the magnetoresistance (MR) effect in ferromagnetic metal/organic molecules/ferromagnetic metal [1]-[4]. Recently we have proposed a spin quantum cross structure (SQCS) device, in which organic molecules are sandwiched between two ferromagnetic thin films with their edges crossed [5]-[7]. The magnetic thin films are made by the evaporation method on polyethylene naphthalate (PEN) substrates. We can make SQCS devices by using the edges of evaporated metal thin films as both the electrodes. Therefore, the area of the cross point of the SQCS device can ultimately be reduced to dimensions in the order of a few square nanometers since the area size is determined by the metal-deposition rate, which can be changed from 0.01 nm/s to the order of 0.1 nm/s. In this paper, we have developed a formula for spin dependent transport in SQCS devices with collinear Ni magnetic electrodes within the framework of the Anderson Hamiltonian, and we have studied the current-voltage characteristics and the MR ratio of SQCS devices with application of the theory. Also, we have realized an SQCS device with Ni magnetic thin-film electrodes, including poly (3-hexylthiophene) (P3HT): 6, 6-phenyl C61-butyric acid methyl ester (PCBM) organic molecules between both the electrodes. It is shown that the experimental results agree very well with the theoretical on
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