Abstract: In A method for measuring a dimensionless coupling constant of a magnetic structure includes the following steps. A step of applying an external vertical magnetic field is performed for enabling magnetic moments of a RE-TM (Rare Earth-Transition metal) alloy magnetic layer of the magnetic structure to be vertical and saturated. A step of measuring a compensation temperature is performed when the sum of the magnetization of the RE-TM alloy magnetic layer is zero. A step of applying an external parallel magnetic field to the RE-TM alloy magnetic layer is performed. A step of adjusting the temperature of the magnetic structure to the compensation temperature and measuring a hysteresis loop of the magnetic structure under the external parallel magnetic field is performed, wherein the inverse of the slope of hysteresis loop is a dimensionless coupling constant.

Abstract: A magnetic stack structure is disclosed. The magnetic stack structure includes two metal layers and a free layer sandwiched by the two metal layers. The thickness of the free layer is 1-30 nm. The thickness of the metal layers are 0.1-20 nm respectively.

Abstract: In A method for measuring a dimensionless coupling constant of a magnetic structure includes the following steps. A step of applying an external vertical magnetic field is performed for enabling magnetic moments of a RE-TM (Rare Earth-Transition metal) alloy magnetic layer of the magnetic structure to be vertical and saturated. A step of measuring a compensation temperature is performed when the sum of the magnetization of the RE-TM alloy magnetic layer is zero. A step of applying an external parallel magnetic field to the RE-TM alloy magnetic layer is performed. A step of adjusting the temperature of the magnetic structure to the compensation temperature and measuring a hysteresis loop of the magnetic structure under the external parallel magnetic field is performed, wherein the inverse of the slope of hysteresis loop is a dimensionless coupling constant.

Abstract: A magnetic stack structure is disclosed. The magnetic stack structure includes two metal layers and a free layer sandwiched by the two metal layers. The thickness of the free layer is 1-30 nm. The thickness of the metal layers are 0.1-20 nm respectively.

Abstract: A magnetic stack structure is disclosed. The magnetic stack structure includes two metal layers and a free layer sandwiched by the two metal layers. The thickness of the free layer is 1-30 nm. The thickness of the metal layers are 0.1-20 nm respectively.

Abstract: A magnetic random access memory includes a substrate, a free layer and a spacer layer. The substrate and the free layer are made of a vertical anisotropy ferrimagentic thin film. The spacer layer is sandwiched between the substrate and the free layer and is made of an insulating layer. The method uses a modified Landau-Lifshitz-Gilbert equation to obtain a critical current value as a function of exchange coupling constant. The critical current value is predictable under several external magnetic fields being applied. When the exchange coupling constant is proportionally varied, the critical current value is reduced to a third of its original value under an optimum state.

Abstract: A magnetic random access memory includes a substrate, a free layer and a spacer layer. The substrate and the free layer are made of a vertical anisotropy ferrimagentic thin film. The spacer layer is sandwiched between the substrate and the free layer and is made of an insulating layer. The method uses a modified Landau-Lifshitz-Gilbert equation to obtain a critical current value as a function of exchange coupling constant. The critical current value is predictable under several external magnetic fields being applied. When the exchange coupling constant is proportionally varied, the critical current value is reduced to a third of its original value under an optimum state.

Abstract: A method for measuring hysteresis curves and anisotropic energy of magnetic memory units is disclosed. It comprises gradually applying different magnetic fields to a single-layer or a multilayer magnetic structure (such as a MRAM memory unit) by extra ordinary Hall effect, and recording the variation of the Hall voltage to obtain the hysteresis curve and anisotropic energy with specific instruments, and calculating the individual anisotropic energy value of the magnetic material of the single-layer or the multilayer magnetic structure.

Abstract: A magnetic tunneling junction structure for magnetic random access memory is disclosed. A composite structure includes at least a pinning layer, a barrier layer, a ferromagnetic layer and a free layer, and the material of the pinning layer and the free layer are perpendicularly anisotropic ferrimagnetic. As the structures include of several barrier layers, free layers and ferrimagnetic layers, that lower coercivity and high squareness for the hysteresis curves can be obtained, and reduction of the coercivity of the free layer can be achieved.

Abstract: A method for measuring hysteresis curves and anisotropic energy of magnetic memory units is disclosed. It comprises gradually applying different magnetic fields to a single-layer or a multilayer magnetic structure (such as a MRAM memory unit) by extra ordinary Hall effect, and recording the variation of the Hall voltage to obtain the hysteresis curve and anisotropic energy with specific instruments, and calculating the individual anisotropic energy value of the magnetic material of the single-layer or the multilayer magnetic structure.

Abstract: A method of measuring sub-micrometer hysteresis loops of a magnetic film is provided. First, a magnetic field is applied to a sample of a magnetic film, and a polarization microscope is used to observe an analytical area of the sample. Next, the observed dynamic video is converted to many digital pictures stored in chronological order. Then, the grayscale values of each selected pixel are read and converted to the corresponding relative magnetic moments, and hysteresis loops of each selected pixel are drawn.