Vladimir Nikitin

Basic principles of STT-MRAM cell operation in memory arrays

For reliable operation, individual cells of an STT-MRAM memory array must meet specific requirements on their performance. In this work we review some of these requirements and discuss the fundamental physical principles of STT-MRAM operation, covering the range from device level to chip array performance, and methodology for its development.

Intrinsic spin dynamics in optically excited nanoscale magnetic tunnel junction arrays restored by dielectric coating

We report the all-optical observation of intrinsic spin dynamics and extraction of magnetic material parameters from arrays of sub-100u2009nm spin-transfer torque magnetic random access memory (STT-MRAM) devices with a CoFeB/MgO interface. To this end, the interference of surface acoustic waves with time-resolved magneto-optic signals via magneto-elastic coupling was suppressed using a dielectric coating. The efficacy of this method is demonstrated experimentally and via modeling on a nickel nanomagnet array. The magnetization dynamics for both coated nickel and STT-MRAM arrays shows a restored field-dependent Kittel mode from which the effective damping can be extracted. We observe an increased low-field damping due to extrinsic contributions from magnetic inhomogeneities and variations in the nanomagnet shape, while the intrinsic Gilbert damping remains unaffected by patterning. The data are in excellent agreement with a local resonance model and have direct implications for the design of STT-MRAM devices a...

Perpendicular magnetic tunnel junction performance under mechanical strain

In this work, we investigate effect of the mechanical stress on the performance of magnetic tunnel junctions with perpendicular magnetic anisotropy. We developed a 4-point bending setup that allows us to apply a constant stress over a large substrate area with access to electrical measurements and an external magnetic field. This setup enables us to measure key device performance parameters, such as tunnel magnetoresistance, switching current ( I c 50%), and thermal stability (Δ), as a function of applied stress. We find that variations in these parameters are negligible: less than 2% over the entire measured range between the zero stress condition and the maximum stress at the point of wafer breakage.In this work, we investigate effect of the mechanical stress on the performance of magnetic tunnel junctions with perpendicular magnetic anisotropy. We developed a 4-point bending setup that allows us to apply a constant stress over a large substrate area with access to electrical measurements and an external magnetic field. This setup enables us to measure key device performance parameters, such as tunnel magnetoresistance, switching current ( I c 50%), and thermal stability (Δ), as a function of applied stress. We find that variations in these parameters are negligible: less than 2% over the entire measured range between the zero stress condition and the maximum stress at the point of wafer breakage.