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With traditional embedded memories, such as eFlash and SRAM, facing major challenge of scaling beyond 28 nm, STT-MRAM stands out from competing emerging NVM technologies as the preferred technology for both embedded flash and SRAM replacements. Having high data retention, reflow compatibility and high endurance, MRAM is ready for production to replace eFlash at 28 nm node and below. On the other end of the spectrum, by tuning magnetic properties of magnetic tunnel junction storage layers, MRAM can achieve high speed/endurance, and offer higher density compared with embedded SRAM at advance nodes.

Stackable 3D cross-point Spin transfer torque magnetic RAM (STT-MRAM) is one of the best candidates to replace DRAM and serve as storage class memory (SCM). For very high density and low cost STT-MRAM, stackable 3D cross-point STT-MRAM architecture requires selectors integrated in series with a magnetic tunneling junction (MTJ) memory element. We have developed a two-terminal bi-directional threshold switching selector and integrated the selector with a perpendicular MTJ to form a 1S1R device. The write operations between "AP" and "P" resistance state have been demonstrated for 1S1R STT-MRAM devices. A simulation model has been developed to simulate conductive filament growth and dissolution process, and dynamic switching of coupled pMTJ and selector devices. The simulation results show the importance of optimal matching of pMTJ magnetic properties with selector resistive properties to achieve high performance.

A conducting 2D electron gas (2DEG) is formed at the interface between epitaxial LaFeO

We use femtosecond time-resolved hard x-ray scattering to detect coherent acoustic phonons generated during ultrafast laser excitation of ferromagnetic bcc Fe films grown on MgO(001). We observe the coherent longitudinal-acoustic phonons as a function of wave vector through analysis of the temporal oscillations in the x-ray scattering signal. The width of the extracted strain wave front associated with this coherent motion is $\ensuremath{\sim}100$ fs. An effective electronic Gr\"uneisen parameter is extracted within a two-temperature model. However, ab initio calculations show that the phonons are nonthermal on the time scale of the experiment, which calls into question the validity of extracting physical constants by fitting such a two-temperature model.

We model room temperature soft x-ray resonant magnetic reflectivity to determine a 24% increase of the Fe magnetic moment of the 2–3 monolayers next to both MgO interfaces in a MgO(3 nm)/Fe(12 nm)/MgO(001) heterostructure. This direct measurement of such enhanced interface magnetic moments for buried interfaces confirms theoretical predictions and highlights the importance of considering inhomogeneous in-depth magnetic profile in Fe/MgO based magnetic tunnel junctions.

High volume spin transfer torque magnetoresistance random access memory (STT-MRAM) for standalone and embedded applications requires a thin perpendicular magnetic tunnel junction (pMTJ) stack (∼10 nm) with a tunnel magnetoresistance (TMR) ratio over 200% after high temperature back-end-of-line (BEOL) processing up to 400 °C. A thin reference layer with low magnetic moment and strong perpendicular magnetic anisotropy (PMA) is key to reduce the total thickness of the full pMTJ stack. We demonstrated strong interfacial PMA and a perpendicular Ruderman-Kittel-Kasuya-Yosida exchange interaction in the Co/Ir system. Owing to the additional high PMA at the Ir/Co interface in combination with a conventional CoFeB/MgO interface in the Ir/Co/Mo/CoFeB/MgO reference layer, the full film pMTJ showed a TMR ratio over 210% after annealing at 400 °C for 150 min. The high TMR ratio can be attributed to the thin stack design by combining a thin reference layer with the efficient compensation by a thin pinned layer. The ann...

The performance of the state-of-the-art perpendicular magnetic tunneling junction (pMTJ) device is fundamentally determined by the physics of material “extreme events.” A dynamic mode approach is used to study “extreme events” of stochastic nonlinear magnetization switching, including magnetic interactions and non-uniform magnetization dynamics. Our theory and experiment show that the magnetization switching “extreme events” are well characterized by the dynamic modes of interacting magnetic systems. The dynamic modes provide a clear understanding of the physical processes of the magnetization switching “extreme events.” We predict markedly different pMTJ scaling behaviors for spin transfer torque, spin-orbit-interaction torque, and thermal fluctuations at different operation speeds and bit error rate conditions. Understanding these scaling behaviors is critical for existing and emerging pMTJ device applications.

A conducting 2D electron gas (2DEG) is formed at the interface between epitaxial LaFeO3 layers >3 unit cells thick and the surface of SrTiO3 single crystals. The 2DEG is exquisitely sensitive to cation intermixing and oxygen nonstoichiometry. It is shown that the latter thus allows the controllable formation of the 2DEG via ionic liquid gating, thereby forming a nonvolatile switch.