The structural, electronic, and magnetic properties of a Mn x Ge 1− x alloy prepared through room-temperature ion implantation (100 keV, 2× 10 16 ions∕ cm 2) and subsequent 400 C annealing have been investigated with several experimental techniques. The as-implanted sample shows a quasi-Gaussian Mn concentration depth profile with a projected range (peak Mn concentration x≃ 12 at.∕%) at 55 nm and end of range at 140 nm. The structural investigation shows that the overall implanted Ge layer is amorphous. In particular, up to a depth of 60 nm, the implanted layer is also porous and oxidized, whereas the deepest implanted region (60–140 nm) is purely composed of amorphous Ge with Mn atoms diluted in it. This sample manifests magnetic hysteresis up to 20 K and a strong nonlinear S-shaped magnetic response up to 150 K. Upon annealing at 400 C, the top porous layer remains essentially …