A manganese-implanted silicon substrate exhibits ferromagnetism and a Curie temperature above room temperature when magnetized. The implant is done at a temperature of between about 250 C and about 800 C, while the manganese concentration is between about 0.01 atomic percent and 10 atomic percent. The silicon substrate can be p- or n-type with a doping concentration between 10.sup.15 and 10.sup.21 cm.sup.-3. Annealing may be done to increase the saturation magnetization.