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In this paper, we have proposed an ultra compact, wide band, and high speed current-controlled magneto-optic (MO) switch based on the optical excitation of surface plasmon polaritons (SPPs) in a magneto-optic metal-insulator-metal (MO-MIM) waveguide. The SPPs are excited on thin metal films in a Kretschmann configuration. For description of device operation, we have derived the dispersion relation with considering MO effects for the mid layer in the five layer surface plasmon polariton (SPP) slab waveguides in a longitudinal configuration which the applied magnetic field is parallel to the layers' interfaces and the longitudinal wave propagation direction. Due to the coupling between SPP modes, there exist all components of the electromagnetic field, hence we do not have purely TM modes in this configuration. For evaluation of the excitation condition, we have used the Rourad's method to calculate the total reflection coefficient due to all layers beyond the interface of the prism and gold where the incident light is launched to the device. The optical response and operation of the device are discussed in terms of dimensions and wavelength. The device operation is based on the variations of the magnetic bias condition by altering the magnetization within the YIG layer. Switching between ON and OFF states is achieved by altering the amplitude of the control current from zero to an appropriate value which the amplitude of the magnetic field bias, changes proportional to the current value. The presented algorithm for analysis of the proposed switch is useful for the design and analysis of any magneto-optic surface plasmon device.