Abstract: Disclosed herein is an optical recording medium comprising a recording layer containing a photochromic material and a polymer which are so combined with each other that a photostationary state attained upon irradiation with light of a specific wavelength is varied with temperatures, a reflective layer for reflecting light which is passed through the recording layer, and a substrate for supporting a laminate of the recording layer and the reflective layer.

Abstract: A recording medium comprises a recording layer, a birefringent layer, and a reflecting layer. The recording layer is formed of a material whose optical rotatory power is alterable such that in one state no optical rotatory power is present and, in a second state, optical rotatory power is present. Information is recorded in the recording layer by selectively altering the state of the recording layer. The birefringent layer is formed of a material having constant birefringence without regard to the state of the recording layer. The reflecting layer reflects a light beam transmitted through the recording layer and the birefringent layer to reintroduce the beam into the birefringent layer and the recording layer. A method of reproducing information from this recording medium applies a polarized light beam to the recording medium and detects change of the polarized state of the polarized light beam reflected from the recording medium, thereby reading the information recorded in the recording layer.

Abstract: Disclosed herein is a recording/reproducing method for an optical recording medium comprising a step of heating a recording layer containing a photochromic material and a polymer which are so combined with each other that a photostationary state attained upon irradiation with light of a specific wavelength is varied with temperatures, and a step of applying the light of a specific wavelength to the heated recording layer for bringing the same into a photostationary state and recording information. In order to reproduce the information, a portion of the recording layer which is in a photostationary state is selectively heated, and reproducing light is applied to reproduce recorded and unrecorded states.

Abstract: A perpendicular magnetic recording medium comprises a non-magnetic substrate having one main surface and a magnetic film of Fe-N or Fe-Co-N formed on the substrate's main surface. The magnetic film includes not only ferromagnetic phase, but also .zeta.-Fe.sub.2 N of paramagnetic phase. The magnetic film is characterized by having columnar crystal structure extending in a direction perpendicular to the substrate's main surface and perpendicular magnetic anisotropy by including .zeta.- Fe.sub.2 N.