Four-State Magnetoresistance in Epitaxial CoFe-Based Magnetic Tunnel Junctions

A four-state magnetic random access memory (MRAM) was developed using an epitaxial Co
₅₀
Fe
₅₀
-MgO-Co
₅₀
Fe
₅₀
magnetic tunnel junction (MTJ) with a tunnel magnetoresistance (TMR) ratio of 145% at room temperature (RT). Four remanent magnetization states in the single-crystalline Co
₅₀
Fe
₅₀
electrode, due to the cubic anisotropy with easy axes of the lang110rang directions, result in four possible angular-dependent TMRs, each separated by more than 20% at RT. Analysis of the asteroid curve for Co
₅₀
Fe
₅₀
indicated that the magnetic field along 22.5deg from the lang110rang directions made it possible to change the magnetization direction of the selected cell without disturbing those of the half-selected cells