Magnetic Properties of Spin Quantum Cross Devices Utilizing Stray Magnetic Fields
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Magnetic Properties of Spin Quantum Cross Devices Utilizing Stray Magnetic Fields Hideo Kaiju1, Haruya Kasa1, Takashi Komine2, Taro Abe1, Takahiro Misawa1, and Junji Nishii1 1 Laboratory of Nanostructured Functional Materials, Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020, Japan 2 Faculty of Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan ABSTRACT We investigate structural and magnetic properties of Co thin-film electrodes used in a new type of spin quantum cross (SQC) devices, in which a strong stray magnetic field could be generated between the both edges of magnetic thin-film electrodes. We also calculate the stray field between the two edges of Co thin-film electrodes in SQC devices and discuss the possibility to novel spintronics devices. As a result of magnetic force microscopy (MFM) observations, the stray fields are generated from the Co edges, and they are uniformly distributed. This result indicates that magnetic single-domain structures can be formed. This is consistent with the result obtained by magneto-optical Kerr effect (MOKE). The theoretical calculation reveals that the stray field exhibits as high as 7000 Oe under the condition that the distance between the two Co edges is 5 nm and the Co thickness is 19 nm. These results indicate that SQC devices utilizing stray fields can be expected as novel spintronics devices, such as spin filtering devices and beyond CMOS switching devices. INTRODUCTION The field of spintronics has attracted much attention due to the discovery of fascinating fundamental phenomena, such as tunnel magnetoresistance (TMR) effect, spin Hall effect, and spin Seebeck effect, and for potential applications in data storage, sensing, beyond CMOS devices, and energy conversion devices [1-5]. Among them, recently, spin quantum cross (SQC) devices, which consist of molecules or metal-oxide insulators sandwiched between two edges of magnetic thin-film electrodes whose edges are crossed, have been proposed as novel nanoscale spintronics devices [6-8]. In SQC devices, the junction area is determined by the thickness of magnetic thin-film electrodes, in other words, 10 nm thick films could produce 10 10 nm2 nanoscale junctions. According to the theoretical calculation, SQC devices exhibit large magnetoresistance (MR) effect at room temperature [6]. In this study, we propose a new type of SQC devices utilizing stray magnetic fields. The new type of SQC devices consists of inorganic complexes or quantum dots sandwiched between two edges of magnetic thin-film electrodes, as shown in figure 1(a). In this device, a high magnetic field could be locally generated in inorganic complexes or quantum dots due to the contribution of the stray field from the both edges of magnetic thin-film electrodes. Since the high magnetic field produces a large Zeeman effect, the energy splitting of the inorganic complexes or quantum dots can be enhanced, as shown in figure 1(b). Therefore, large spin filtering effects can be expected. As the first att
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