We define a specific class of fractals as "net fractals" and prove that in the logarithmic scale they are isomorphic with some bulk crystals. Furthermore, with the use of logarithmic coordinates, we prove that in the "net fractal" magnetic system the indirect exchange, by itinerant electrons can be presented in the form that is reminiscent of the Ruderman-Kittel-Kasuya-Yosida interaction characteristic of a system of fractional spectral dimension.