Magnetic Memory Devices with Tunnel Barriers for High Magnetoresistance

The magnetic memory device is segmented into multiple functional magnetic layers (first magnetic layer, second magnetic layer, third magnetic layer) separated by distinct tunnel barriers and non-magnetic layers. Each layer serves a specific function: the first magnetic layer provides reference magnetization, the second magnetic layer provides free magnetization for data storage, and the third magnetic layer provides additional magnetic anisotropy. This segmentation allows independent optimization of each layer's properties to achieve high reliability and magnetoresistance ratio while managing complexity through modular design

The patent employs composite magnetic structures where ferromagnetic layers (containing Co, Fe, Ni) are combined with non-magnetic spacer layers (Ru, Ta, Pt) and insulating tunnel barriers (MgO, Al2O3). The ferromagnetic layers provide magnetic moment and anisotropy, the non-magnetic layers provide exchange coupling and structural stability, and the tunnel barriers provide electrical isolation and magnetoresistance effect. This composite material approach enables simultaneous achievement of high reliability, high magnetoresistance ratio, and controlled device complexity

The patent utilizes parameter changes in the magnetic layers' physical and magnetic properties to achieve high reliability with controlled power consumption. Specifically, the thickness of ferromagnetic layers is optimized (e.g., CoFeB layer thickness of 3-5 nm), the magnetization strength of each layer is tuned through composition control, and the tunnel barrier thickness is precisely controlled (e.g., MgO barrier of 1-3 nm). These parameter optimizations enable high magnetoresistance ratio for reliable data storage while minimizing the current required for magnetization switching, thus controlling operating power

Non-magnetic spacer layers (such as Ru, Ta, or Pt layers with thickness of 0.5-2 nm) are introduced as intermediaries between the ferromagnetic layers. These intermediary layers provide exchange coupling that stabilizes the relative magnetization directions between adjacent magnetic layers, enhancing data storage reliability. Simultaneously, they act as diffusion barriers and reduce the direct magnetic interaction that would require higher switching currents, thus helping to control operating power consumption

The patent applies local quality by creating specific crystal structures in localized regions of the magnetic layers. The tunnel barrier layers (MgO, Al2O3) are grown with specific crystal orientations ((001) plane) to induce vertical magnetic anisotropy in the adjacent ferromagnetic layers. The ferromagnetic layers themselves are engineered with specific crystal structures (L10, HCP, or BCC) in the regions where vertical anisotropy is needed, while other regions may have different structures. This localized control of crystal quality enables high magnetoresistance ratio through enhanced vertical anisotropy while allowing flexibility in manufacturing processes

The patent employs self-service mechanisms where the growth of one layer automatically induces the desired crystal structure and orientation in subsequent layers. For example, the epitaxial growth of MgO tunnel barrier with (001) orientation automatically induces vertical magnetic anisotropy in the CoFeB ferromagnetic layer grown on top of it, without requiring additional processing steps. The spinodal decomposition in CoFeB layers during annealing automatically creates the desired L10 or HCP crystal structures with vertical anisotropy. These self-organizing processes reduce the need for high-precision external control during manufacturing