Thermally assisted MRAM

Abstract

Magnetic random access memories (MRAMs) are a new non-volatile memory technology trying establish itself as a mainstream technology. MRAM cell operation using a thermally assisted writing scheme (TA-MRAM) is described in this review as well as its main design challenges. This approach is compared to conventional MRAM, highlighting the improvements in write selectivity, power consumption and thermal stability. The TA-MRAM writing was tested and validated in the dynamic regime down to 500 ps write pulses. The heating process was investigated for the influence of the voltage pulse width, junction area and lead volume looking at the required write power density. The possibilities to control and reduce the write power density are described. The most promising solution to optimize the heating process and reduce the power consumption is to insert two thermal barrier layers at both ends of the MTJ layer stack, between the junction and the electrical leads, using low thermal conductivity materials. This minimizes the heating losses and improves the heating efficiency.

Significant reduction of critical currents in MRAM designs using dual free layer with perpendicular and in-plane anisotropy

“…The spin torque efficiency could be improved by thermally assisted switching designs [ 3 ]. Here, on top of the free layer an antiferromagnet is deposited which stabilizes the free layer due to exchange bias.…”

Bias-controlled ultrafast demagnetization in magnetic tunnel junctions

“…This implies that, in a multilayer system, a contribution (up to about 40%) to ultrafast demagnetization may be due to transport phenomena. Our results imply the possibility of optically addressed spintronic devices which may benefit in speed of operation and performances compared to their all-electric analogs [14,15].…”

“…For instance, assuming the reported bias-modulated demagnetization effects could be extended to ultrafast optically induced magnetization reversal, we might possibly illuminate large MTJ arrays with a single laser pulse and electrically address only selected devices. One might thus obtain a faster version of heat-assisted solid-state memories [14,34] where the size of the memory cells would not be limited by diffraction, with the possibility of operating massively parallel memory switching.…”

Study of Spin Transfer Torque (STT) and Spin Orbit Torque (SOT) Magnetic Tunnel Junctions (MTJS) at Advanced CMOS Technology Nodes

“…The early generation of MTJs commercialized by Everspin, was based on Field Induced Magnetic Switching (FIMS) [2] writing scheme. A later improvement was proposed by Crocus by thermally assisting the writing operation (TAS) [3]. The high switching current of FIMS (>10mA) and TAS (>1mA) limits significantly their future use for memory application and bring the dynamic power issue for the logic circuits.…”