Three-valued magnetic tunnel junction for nonvolatile ternary content addressable memory application

Three-valued epitaxial $Co50Fe50/MgO/Co50Fe50$ magnetic tunnel junctions (MTJs) were developed for nonvolatile ternary content addressable memory (TCAM) application. Four remanent magnetization states in the single-crystalline $Co50Fe50$ electrode, due to cubic anisotropy with easy axes of the $⟨110⟩$ directions, result in four possible angular-dependent tunnel magnetoresistance ratios. Three states selected from among the four states were separated by more than 56% at room temperature. Analysis of the asteroid curve for $Co50Fe50$ indicated that a magnetic field along $22.5°$ from the $⟨110⟩$ directions made it possible to change the magnetization direction of the selected cell without disturbing those of the half-selected cells in the MTJ arrays. A nonvolatile TCAM cell using the three-valued MTJ for three-level data storage was proposed, and its operation was verified by circuit simulation. The TCAM cell reduces the device count to 5, a value 1/3 that of conventional complementary metal-oxide semiconductor-based TCAMs.