TY - JOUR
T1 - Predictive Materials Design of Magnetic Random-Access Memory Based on Nanoscale Atomic Structure and Element Distribution
AU - Li, Xiang
AU - Sasaki, Taisuke
AU - Grezes, Cecile
AU - Wu, Di
AU - Wong, Kin
AU - Bi, Chong
AU - Ong, Phuong Vu
AU - Ebrahimi, Farbod
AU - Yu, Guoqiang
AU - Kioussis, Nicholas
AU - Wang, Weigang
AU - Ohkubo, Tadakatsu
AU - Khalili Amiri, Pedram
AU - Wang, Kang L.
N1 - Funding Information:
This work was partially supported by the NSF Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems (TANMS). The work at Inston was supported in part by a Phase II NSF Small Business Innovation Research award. NSF supports the work at the University of Arizona through ECCS-1554011. We want to acknowledge the collaboration of this research with the King Abdul-Aziz City for Science and Technology (KACST) via The Center of Excellence for Green Nanotechnologies (CEGN). This work was partially supported by the Energy Frontier Research Center for Spins and Heat in Nanoscale Electronic Systems (SHINES). The authors would also like to acknowledge Kazuhiro Hono, Sarah Tolbert, Gregory Carman, Sohee Kwon, and Shy-Jay Lin for fruitful discussions.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/12/11
Y1 - 2019/12/11
N2 - Magnetic tunnel junctions (MTJs) capable of electrical read and write operations have emerged as a canonical building block for nonvolatile memory and logic. However, the cause of the widespread device properties found experimentally in various MTJ stacks, including tunneling magnetoresistance (TMR), perpendicular magnetic anisotropy (PMA), and voltage-controlled magnetic anisotropy (VCMA), remains elusive. Here, using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy, we found that the MTJ crystallization quality, boron diffusion out of the CoFeB fixed layer, and minimal oxidation of the fixed layer correlate with the TMR. As with the CoFeB free layer, seed layer diffusion into the free layer/MgO interface is negatively correlated with the interfacial PMA, whereas the metal-oxides concentrations in the free layer correlate with the VCMA. Combined with formation enthalpy and thermal diffusion analysis that can explain the evolution of element distribution from MTJ stack designs and annealing temperatures, we further established a predictive materials design framework to guide the complex design space explorations for high-performance MTJs. On the basis of this framework, we demonstrate experimentally high PMA and VCMA values of 1.74 mJ/m2 and 115 fJ/V·m-1 with annealing stability above 400 °C.
AB - Magnetic tunnel junctions (MTJs) capable of electrical read and write operations have emerged as a canonical building block for nonvolatile memory and logic. However, the cause of the widespread device properties found experimentally in various MTJ stacks, including tunneling magnetoresistance (TMR), perpendicular magnetic anisotropy (PMA), and voltage-controlled magnetic anisotropy (VCMA), remains elusive. Here, using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy, we found that the MTJ crystallization quality, boron diffusion out of the CoFeB fixed layer, and minimal oxidation of the fixed layer correlate with the TMR. As with the CoFeB free layer, seed layer diffusion into the free layer/MgO interface is negatively correlated with the interfacial PMA, whereas the metal-oxides concentrations in the free layer correlate with the VCMA. Combined with formation enthalpy and thermal diffusion analysis that can explain the evolution of element distribution from MTJ stack designs and annealing temperatures, we further established a predictive materials design framework to guide the complex design space explorations for high-performance MTJs. On the basis of this framework, we demonstrate experimentally high PMA and VCMA values of 1.74 mJ/m2 and 115 fJ/V·m-1 with annealing stability above 400 °C.
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U2 - 10.1021/acs.nanolett.9b03190
DO - 10.1021/acs.nanolett.9b03190
M3 - Article
C2 - 31697502
AN - SCOPUS:85075698653
VL - 19
SP - 8621
EP - 8629
JO - Nano Letters
JF - Nano Letters
SN - 1530-6984
IS - 12
ER -