Magnetic recording medium includes at least two layers having different magnetic anisotropy constants formed on a substrate and the perpendicular magnetic anisotropy of the second magnetic film of those magnetic films, far from the substrate surface, made equal to or larger than that of the first magnetic film near to the substrate surface, thus improving the magnetic isolation. The process comprises plating the metal surface with a layer of electroless nickel, electroless cobalt or electroless tin followed by phosphating the plated layer prior to bonding the polymeric material thereto. The device can be an instrument for measuring strain in the sample, or for measuring other properties or attributes of a sample, such as temperature. The rotor rotation speed is reduced when the total load value is above a first limit value. Part of the piston retainer portion extends radially inward relative to the interior surface of the cylinder portion farther than a portion of the piston such that the piston cannot slide completely past the piston retainer portion. A light emitting diode is coupled to the first PN junction diode to provide a current sense threshold substantially proportional to a difference between a forward voltage drop of the LED and a forward voltage drop of the first PN junction diode.