Three-state memory combining resistive and magnetic switching using tunnel junctions

Abstract

Magnetic fields generated by current lines are the standard way of switching between resistance (R) states in magnetic random access memories. A less common but technologically more interesting alternative to achieve R-switching is to use an electrical current crossing the tunnel barrier. Such current induced magnetization switching (CIMS) or current induced switching (CIS) effects were recently observed in thin magnetic tunnel junctions, and attributed to spin transfer (CIMS) or electromigration of atoms into the insulator (CIS). In this work, electromigration-driven resistance changes (resistive switching) are superimposed with thermally induced pinned layer reversal (magnetic switching), producing a reproducible, three-state memory device. The tunnel junctions under study show a tunnel magnetoresistance of 14% with a RA product of 50 µm 2. The reversible electromigration-driven resistance changes amount to 7-8% of the full resistance change and more than 10 4 R-switching events can be current induced without significant damage to the tunnel junction. Typical critical current densities are of the order of 2 × 10 6 A cm −2 .

Simulations of refrigeration on integrated circuits using micro-channels

“…(1), one can extract a characteristic temperature variation time, t à ¼ qC k . We expanded a finite element program [10][11][12] to solve the temperature evolution Eq. (1) using a triangular mesh with a dt step of 0.0001 and relative tolerance of 0.01.…”

Three-state dual spin valve structure

“…Binary memory states currently dominate but multistate memory has been receiving much attention, because it offers excellent storage density. [15][16][17] Although the possibility of fabricating a multistate magnetic device has been demonstrated, these devices, are however, hard to adapt for practical use because of the inability to selectively switch single elements in a multi-level stack. In a half-select MRAM switching scheme, the field from bit and word lines disturbs more than one element in the stack.…”

Asymmetric electromigration-driven resistive switching in tunnel junctions

“…These devices usually consist of simple metal-insulatormetal sandwiches and large reversible resistance (R) changes can be induced by an electrical current. Insulating materials can be as diversified as CuO [2], ZnO [3], NiO [4], TiO 2 [5], MgO [6], Al 2 O 3 [7,8], SiO 2 [9] or organic films [10]. However, the microscopic origin of the R-switching mechanism is still unclear and several models have been proposed [11], such as charge trapping at interfacial sites [12], a Mott metal-insulator transition [13] or metallic filamentary path formation/rupture [14].…”