Coherent magnetization reversal of a cylindrical nanomagnet in shape-anisotropy magnetic tunnel junctions

A shape-anisotropy magnetic tunnel junction (MTJ) holds promise for its scaling into single-digit nanometers while possessing high data-retention capability. Understanding magnetization reversal mode is crucial to quantify the thermal stability factor Δ for data retention with high accuracy. Here, we study magnetization reversal mode in the shape-anisotropy MTJ with a 15-nm-thick CoFeB layer by evaluating Δ from two different methods: switching probability and retention time measurements. We find that magnetization reversal coherently proceeds in the 15-nm-thick and X/1X-nm-diameter cylindrical nanomagnet in the shape-anisotropy MTJs, in contrast to the conventional interfacial-anisotropy MTJs with a smaller thickness and larger diameter. The coherent magnetization reversal of the shape-anisotropy MTJ is also confirmed by astroid curve measurements. This study provides insight into the development of ultrasmall and high-reliability MTJ devices.

[1]  H. Ohno,et al.  Temperature dependence of the energy barrier in X/1X nm shape-anisotropy magnetic tunnel junctions , 2021 .

[2]  J. Katine,et al.  Thermal stability for domain wall mediated magnetization reversal in perpendicular STT MRAM cells with W insertion layers , 2020, Applied Physics Letters.

[3]  T. Endoh,et al.  Micromagnetic simulation of the temperature dependence of the switching energy barrier using string method assuming sidewall damages in perpendicular magnetized magnetic tunnel junctions , 2020 .

[4]  Hideo Ohno,et al.  Scaling magnetic tunnel junction down to single-digit nanometers—Challenges and prospects , 2020 .

[5]  D. Apalkov,et al.  Atomistic investigation of the temperature and size dependence of the energy barrier of CoFeB/MgO nanodots , 2019, Journal of Applied Physics.

[6]  B. Hughes,et al.  Demonstration of a Reliable 1 Gb Standalone Spin-Transfer Torque MRAM For Industrial Applications , 2019, 2019 IEEE International Electron Devices Meeting (IEDM).

[7]  S. O. Park,et al.  1Gbit High Density Embedded STT-MRAM in 28nm FDSOI Technology , 2019, 2019 IEEE International Electron Devices Meeting (IEDM).

[8]  B. Diény,et al.  Perpendicular shape anisotropy spin transfer torque-MRAM: determination of pillar tilt angle from 3D Stoner–Wohlfarth astroid analysis , 2019, Journal of Physics D: Applied Physics.

[9]  H. Ohno,et al.  Write-error rate of nanoscale magnetic tunnel junctions in the precessional regime , 2019, Applied Physics Letters.

[10]  C. Yoshida,et al.  Micromagnetic Study of Edge-Damage Effects in Perpendicular CoFeB/MgO Magnetic Tunnel Junction , 2019, IEEE Transactions on Magnetics.

[11]  T. Endoh,et al.  14ns write speed 128Mb density Embedded STT-MRAM with endurance>1010 and 10yrs retention@85°C using novel low damage MTJ integration process , 2018, 2018 IEEE International Electron Devices Meeting (IEDM).

[12]  Weisheng Zhao,et al.  Modeling and Evaluation of Sub-10-nm Shape Perpendicular Magnetic Anisotropy Magnetic Tunnel Junctions , 2018, IEEE Transactions on Electron Devices.

[13]  T. Endoh,et al.  Novel Method of Evaluating Accurate Thermal Stability for MTJs Using Thermal Disturbance and its Demonstration for Single-/Double-Interface p-MTJ , 2018, IEEE Transactions on Magnetics.

[14]  B. Diény,et al.  A highly thermally stable sub-20 nm magnetic random-access memory based on perpendicular shape anisotropy. , 2018, Nanoscale.

[15]  H. Ohno,et al.  Shape anisotropy revisited in single-digit nanometer magnetic tunnel junctions , 2017, Nature Communications.

[16]  H. Ohno,et al.  Magnetic-field-angle dependence of coercivity in CoFeB/MgO magnetic tunnel junctions with perpendicular easy axis , 2017 .

[17]  H. Ohno,et al.  Magnetic and Free-Layer Properties of MgO/(Co)FeB/MgO Structures: Dependence on CoFeB Composition , 2017, IEEE Magnetics Letters.

[18]  H. Ohno,et al.  Evaluation of energy barrier of CoFeB/MgO magnetic tunnel junctions with perpendicular easy axis using retention time measurement , 2017 .

[19]  D. Apalkov,et al.  Thermally nucleated magnetic reversal in CoFeB/MgO nanodots , 2017, Scientific Reports.

[20]  V. Nikitin,et al.  Material Developments and Domain Wall-Based Nanosecond-Scale Switching Process in Perpendicularly Magnetized STT-MRAM Cells , 2017, IEEE Transactions on Magnetics.

[21]  T. Devolder,et al.  Size dependence of nanosecond-scale spin-torque switching in perpendicularly magnetized tunnel junctions , 2016, 1607.00260.

[22]  Tom Zhong,et al.  Achieving Sub-ns switching of STT-MRAM for future embedded LLC applications through improvement of nucleation and propagation switching mechanisms , 2016, 2016 IEEE Symposium on VLSI Technology.

[23]  Tom Zhong,et al.  Solving the paradox of the inconsistent size dependence of thermal stability at device and chip-level in perpendicular STT-MRAM , 2015, 2015 IEEE International Electron Devices Meeting (IEDM).

[24]  Seung H. Kang,et al.  Systematic optimization of 1 Gbit perpendicular magnetic tunnel junction arrays for 28 nm embedded STT-MRAM and beyond , 2015, 2015 IEEE International Electron Devices Meeting (IEDM).

[25]  Hideo Ohno,et al.  Temperature dependence of energy barrier in CoFeB-MgO magnetic tunnel junctions with perpendicular easy axis , 2015 .

[26]  GABRIEL CHAVES-O’FLYNN,et al.  Thermal Stability of Magnetic States in Circular Thin-Film Nanomagnets with Large Perpendicular Magnetic Anisotropy , 2015 .

[27]  Kyung-Jin Lee,et al.  Spin-transfer-torque efficiency enhanced by edge-damage of perpendicular magnetic random access memories , 2015, 1507.05276.

[28]  Shoji Ikeda,et al.  Properties of magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure down to junction diameter of 11 nm , 2014 .

[29]  H. Ohno,et al.  Perpendicular-anisotropy CoFeB-MgO magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure , 2012 .

[30]  W. Rippard,et al.  Thermal relaxation rates of magnetic nanoparticles in the presence of magnetic fields and spin-transfer effects , 2011, 1107.5007.

[31]  Shoji Ikeda,et al.  Magnetic tunnel junction for nonvolatile CMOS logic , 2010, 2010 International Electron Devices Meeting.

[32]  H. Ohno,et al.  A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction. , 2010, Nature materials.

[33]  G. Hu,et al.  Angular dependence of the switching field in patterned magnetic elements , 2005 .

[34]  J. Lodder,et al.  Magnetization process of high anisotropy CoPt nanosized dots , 2005, IEEE Transactions on Magnetics.

[35]  S. Zhang,et al.  Thermally assisted magnetization reversal in the presence of a spin-transfer torque , 2003, cond-mat/0302339.

[36]  H. Pfeiffer,et al.  Determination of anisotropy field distribution in particle assemblies taking into account thermal fluctuations , 1990 .