We have proposed spin quantum cross (SQC) devices, in which organic materials are sandwiched between two edges of magnetic thin films whose edges are crossed, towards the realization of novel beyond-CMOS switching devices. In SQC devices, nanometer-size junctions can be produced since the junction area is determined by the film thickness. In this study, we have fabricated Ni SQC devices with poly-3-hexylthiophene (P3HT): 6, 6-phenyl C61-butyric acid methyl ester (PCBM) organic materials and investigated the current-voltage (I-V) characteristics experimentally and theoretically. As a result of I-V measurements, ohmic I-V characteristics have been obtained at room temperature for Ni SQC devices with P3HT:PCBM organic materials, where the junction area is as small as 16 nm x 16 nm. This experimental result shows quantitative agreement with the theoretical calculation results performed within the framework of the Anderson model under the strong coupling limit. Our calculation also shows that a high onZoff ratio beyond 10000:1 can be obtained in Ni SQC devices with P3HT:PCBM organic materials under the weak coupling condition.