Described is a piston rod position-sensing system having a cylinder and piston rod arranged in the cylinder for movement with respect thereto. A magnetically hard layer is formed on the piston rod to provide a recording medium. The magnetically hard layer is made of a cobalt-phosphorous (Co--P)-based alloy. A magnetic pattern is recorded in the magnetically hard layer. A magnetic field sensor located in the cylinder senses the recorded magnetic pattern while the piston rod is moving with respect to the cylinder. Signals are generated in response to the sensed magnetic pattern for determining a position of the piston rod