Design considerations for MRAM

Abstract

MRAM (magnetic random access memory) technology, based on the use of magnetic tunnel junctions (MTJs) as memory elements, is a potentially fast nonvolatile memory technology with very high write endurance. This paper is an overview of MRAM design considerations. Topics covered include MRAM fundamentals, array architecture, several associated design studies, and scaling challenges. In addition, a 16-Mb MRAM demonstration vehicle is described, and performance results are presented.

Proposal for a standard problem for micromagnetic simulations including spin-transfer torque

“…In accordance with the simulations of standard problem numbers [1][2][3][4] 26 these results illustrate, that to obtain reliable numerical results the distance between two discretization points should be significantly below the exchange length l ex .…”

“…At the intersection of the two wires, the resulting Oersted field is strong enough to switch the magnetic orientation of the first magnetic layer, the so-called free layer. The magnetic orientation of the second ferromagnetic layer, the so-called pinned layer, should not change during this process 3,6 . The application of an Oersted field corresponds to the write process in a hard disk.…”

Low-Energy Truly Random Number Generation with Superparamagnetic Tunnel Junctions for Unconventional Computing

“…Therefore, in the context of random number generators, extreme scaling of the nanodevices appears as providential, as smaller volumes and areas are directly linked to a lower magnetization stability of the free magnet 40 , increasing random bit generation speed exponentially. This is in sharp contrast with MRAMs, where conservation of stability with extreme scaling is an important challenge 41 .…”

Multilevel 3 Bit-per-cell Magnetic Random Access Memory Concepts and Their Associated Control Circuit Architectures

“…A single bit per cell MRAM [7,8] has been commercially available since 2006 and has already found a market in data critical systems [9][10][11]. Unfortunately, problems have been encountered in increasing the density of existing MRAM.…”

“…The properties of the dielectric spacer layer and quality of the interfaces between the spacer layer and magnetic layers are crucial in determining the resistance ratio of the structure [28]. TMR ratios of up 70% are possible for Al 2 O 3 (alumina) and up to 600% for crystalline MgO dielectric barriers [4,7,8,29,30]. These materials therefore open up the possibility of the accurate discrimination of intermediate resistance states making multi-level MRAM an exciting workable possibility for increasing memory density.…”