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.