Four-State Magnetic Random Access Memory and Ternary Content Addressable Memory Using CoFe-Based Magnetic Tunnel Junctions

A four-state magnetic random access memory (MRAM) and ternary content addressable memory (TCAM) were developed using epitaxial Co₅₀Fe₅₀/MgO/Co₅₀Fe₅₀ magnetic tunnel junctions with a tunnel magnetoresistance (TMR) ratio of 145% at room temperature (RT). Four remanent magnetization states in the single-crystalline CoS0FeS0 electrode, due to the cubic anisotropy with easy axes of the (110) directions, result in four possible angular-dependent TMRs, each separated by more than 20% at RT. Analysis of the asteroid curve for Co₅₀Fe₅₀ indicated that the magnetic field along 22.5deg from the (110) directions made it possible to change the magnetization direction of the selected cell without disturbing those of the half-selected cells. The proposed non-volatile TCAM cell reduced the device count to 5, a value 1/3 compared to the conventional CMOS-based TCAMs.