Patent ID: 8105704
Filing Date: 2012-01-31
Classification: C01G,C01P,G11B,H01F,Y10T

Abstract:
1. A nonvolatile phase change magnetic memory, comprising: a substrate; and a non-volatile magnetic memory layer on said substrate, the non-volatile magnetic memory layer being made of a crystalline non-stoichiometric transition metal chalcogenide binary compound, which in composition is deficient in transition metal from its stoichiometric ratio composition, wherein the crystalline transition metal chalcogenide binary compound is expressed by formula: Fe wherein said crystalline transition metal chalcogenide compound is structured such that spins of the transition metal atoms in each crystallographic c-plane are ferromagnetically coupled to each other, and spins of the transition metal in each crystallographic c-plane are antiferromagnetically coupled to spins of the transition metal atoms in an adjacent crystallographic c-plane, wherein said crystalline transition metal chalcogenide compound has first and second phases: the first phase having an ordered distribution of the vacancies at the transition metal sites such that the c-plane that has the vacancies at the transition metal atom sites occurs periodically in every other c-plane along an c-axis so that said crystalline transition metal compound exhibits ferromagnetism, a second phase thereof having a disordered distribution of the vacancies in the transition metal sites such that the vacancies at the transition metal sites are distributed randomly relative to the first phase so that said crystalline transition metal compound exhibits antiferromagnetism, wherein said crystalline transition metal chalcogenide compound in said first phase is transformed to said second phase when a first temperature history is applied thereto, and said crystalline transition metal chalcogenide compound in said second phase is transformed to said first phase when a second temperature history is applied thereto, wherein said first temperature history comprises heating the crystalline transition metal chalcogenide compound to a temperature at which said ordered distribution of the vacancies at the transition metal sites vanishes, followed by rapid cooling, wherein such second temperature history includes one of first and second sequences, the first sequence comprising heating the crystalline transition metal chalcogenide compound to a temperature at which said vacancies at the transition metal sites diffuse to exhibit said ordered distribution of the vacancies, followed by cooling, the second sequence comprising heating the crystalline transition metal chalcogenide compound to a temperature at which said ordered distribution of the vacancies at the transition metal sites vanishes, followed by cooling said crystalline transition metal chalcogenide compound at such a rate as to produce said ordered distribution of the vacancies at the transition metal sites upon cooling, and wherein said non-volatile magnetic memory layer has ferromagnetic portions in which said crystalline transition metal chalcogenide compound is in its first phase, and antiferromagnetic portions in which said crystalline transition metal chalcogenide compound is in its second phase to represent information by a spatial distribution of said ferromagnetic portions and said antiferromagnetic portions.