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A compact model for magnetic tunnel junction (MTJ) switched by thermally assisted Spin transfer torque (TAS + STT).

Zhao W, Duval J, Klein JO, Chappert C - Nanoscale Res Lett (2011)

Bottom Line: Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density.In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models.Many experimental parameters are included directly to improve the simulation accuracy.

View Article: PubMed Central - HTML - PubMed

Affiliation: IEF, Université Paris-Sud, 15 Rue Georges Clemenceau, Orsay, 91405, France. weisheng.zhao@u-psud.fr.

ABSTRACT
Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density. In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models. Many experimental parameters are included directly to improve the simulation accuracy. It is programmed in the Verilog-A language and compatible with the standard IC CAD tools, providing an easy parameter configuration interface and allowing high-speed co-simulation of hybrid MTJ/CMOS circuits.

No MeSH data available.


Related in: MedlinePlus

Transient simulation of compact model. (a) and (b) Control signals activate the circuit to generate bidirectional currents. (c) MTJ is switched between the P and AP. (d) Temperature evaluation. (e) The state of MTJ. P, parallel; AP, anti-parallel.
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Figure 3: Transient simulation of compact model. (a) and (b) Control signals activate the circuit to generate bidirectional currents. (c) MTJ is switched between the P and AP. (d) Temperature evaluation. (e) The state of MTJ. P, parallel; AP, anti-parallel.

Mentions: This compact model has been developed in Verilog-A language and implemented on Cadence Virtuoso CAD platform [21]. Its default parameters correspond to a MTJ nanopillar BiFe(10)/IrMn(6)/CoFeB(1)/MgO(0.85)/CoFeB(3)/PtMn(6). Thanks to the graphical parameter configuration of Verilog-A, MTJ can be set easily with different material and process parameters. By using CMOS 65 nm design-kit, a simple hybrid circuit (see Figure 2b) [22] has been successfully simulated (see Figure 3), which validates the functionalities and behaviours of this model. The voltage pulse "Vg1" is activated at 40 ns and Iswitch begins to heat the MTJ from ambient temperature. As its temperature reaches up to Tb2 after ~11.22 ns, the model compares the Iswitch (approx 462.9 uA) with the STT critical current IC (~150 uA) and switches the state of MTJ from parallel [P] to anti-parallel [AP] state in about 6 ns according to the STT dynamic model. As "Vg1" is deactivated, MTJ begins to cool down to ambient temperature. The state can be reversed from AP to P by activating the control signal "Vg2", which generates Iswitch (approx-375.6uA). The Iswitch values are asymmetric as a constant voltage supply is used in the simulation (e.g. 1V) and the resistance of MTJ changes between two states (RP and RAP). It is important to note that the voltage pulse width should be longer than Dheat+Dswitch to ensure the reliable switching operation [5].


A compact model for magnetic tunnel junction (MTJ) switched by thermally assisted Spin transfer torque (TAS + STT).

Zhao W, Duval J, Klein JO, Chappert C - Nanoscale Res Lett (2011)

Transient simulation of compact model. (a) and (b) Control signals activate the circuit to generate bidirectional currents. (c) MTJ is switched between the P and AP. (d) Temperature evaluation. (e) The state of MTJ. P, parallel; AP, anti-parallel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211458&req=5

Figure 3: Transient simulation of compact model. (a) and (b) Control signals activate the circuit to generate bidirectional currents. (c) MTJ is switched between the P and AP. (d) Temperature evaluation. (e) The state of MTJ. P, parallel; AP, anti-parallel.
Mentions: This compact model has been developed in Verilog-A language and implemented on Cadence Virtuoso CAD platform [21]. Its default parameters correspond to a MTJ nanopillar BiFe(10)/IrMn(6)/CoFeB(1)/MgO(0.85)/CoFeB(3)/PtMn(6). Thanks to the graphical parameter configuration of Verilog-A, MTJ can be set easily with different material and process parameters. By using CMOS 65 nm design-kit, a simple hybrid circuit (see Figure 2b) [22] has been successfully simulated (see Figure 3), which validates the functionalities and behaviours of this model. The voltage pulse "Vg1" is activated at 40 ns and Iswitch begins to heat the MTJ from ambient temperature. As its temperature reaches up to Tb2 after ~11.22 ns, the model compares the Iswitch (approx 462.9 uA) with the STT critical current IC (~150 uA) and switches the state of MTJ from parallel [P] to anti-parallel [AP] state in about 6 ns according to the STT dynamic model. As "Vg1" is deactivated, MTJ begins to cool down to ambient temperature. The state can be reversed from AP to P by activating the control signal "Vg2", which generates Iswitch (approx-375.6uA). The Iswitch values are asymmetric as a constant voltage supply is used in the simulation (e.g. 1V) and the resistance of MTJ changes between two states (RP and RAP). It is important to note that the voltage pulse width should be longer than Dheat+Dswitch to ensure the reliable switching operation [5].

Bottom Line: Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density.In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models.Many experimental parameters are included directly to improve the simulation accuracy.

View Article: PubMed Central - HTML - PubMed

Affiliation: IEF, Université Paris-Sud, 15 Rue Georges Clemenceau, Orsay, 91405, France. weisheng.zhao@u-psud.fr.

ABSTRACT
Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density. In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models. Many experimental parameters are included directly to improve the simulation accuracy. It is programmed in the Verilog-A language and compatible with the standard IC CAD tools, providing an easy parameter configuration interface and allowing high-speed co-simulation of hybrid MTJ/CMOS circuits.

No MeSH data available.


Related in: MedlinePlus