open access publication

Article, 2023

Enhancing spin-transfer torque in magnetic tunnel junction devices: Exploring the influence of capping layer materials and thickness on device characteristics

Journal of Applied Physics, ISSN 0021-8979, 1089-7550, Volume 133, 24, Page 243902, 10.1063/5.0151480

Contributors

Parvini, Tahereh Sadat (Corresponding author) [1] Paz, Elvira 0000-0003-0908-9948 [2] Böhnert, Tim 0000-0002-2659-1481 [2] Schulman, Alejandro 0000-0002-8053-2626 [2] Benetti, Luana Carina 0000-0003-3063-957X [2] Oberbauer, Felix [1] Walowski, Jakob 0000-0003-4202-5612 [1] Moradi, Farshad 0000-0001-7077-8545 [3] Ferreira, Ricardo 0000-0003-0953-2225 [2] Münzenberg, Markus G 0000-0002-1332-5678 [1]

Affiliations

  1. [1] University of Greifswald
  2. [NORA names: Germany; Europe, EU; OECD];
  3. [2] International Iberian Nanotechnology Laboratory
  4. [NORA names: Portugal; Europe, EU; OECD];
  5. [3] Aarhus University
  6. [NORA names: AU Aarhus University; University; Denmark; Europe, EU; Nordic; OECD]

Abstract

We have developed and optimized two categories of spin-ransfer torque magnetic tunnel junctions (STT-MTJs) that exhibit a high tunnel magnetoresistance ratio, low critical current, high outputpower in the micro-watt range, and auto-oscillation behavior. These characteristics demonstrate the potential of STT-MTJs for low-power, high-speed, and reliable spintronic applications, including magnetic memory, logic, and signal processing. The only distinguishing factor between the two categories, denoted as A-MTJs and B-MTJs, is the composition of their free layers, two CoFeB/0.21 Ta/6 CoFeSiB for A-MTJs and two CoFeB/0.21 Ta/7 NiFe for B-MTJs. Our study reveals that B-MTJs exhibit lower critical currents for auto-oscillation than A-MTJs. We found that both stacks have comparable saturation magnetization and anisotropy field, suggesting that the difference in auto-oscillation behavior is due to the higher damping of A-MTJs compared to B-MTJs. To verify this hypothesis, we employed the all-optical time-resolved magneto-optical Kerr effect technique, which confirmed that STT-MTJs with lower damping exhibited auto-oscillation at lower critical current values. Additionally, our study aimed to optimize the STT-MTJ performance by investigating the impact of the capping layer on the device’s response to electronic and optical stimuli.

Keywords

CoFeSiB, Kerr effect technique, NiFe, STT-MTJ, anisotropy, anisotropy field, applications, auto-oscillations, behavior, capping layer, categories, characteristics, composition, current, damping, device characteristics, device response, devices, effective technique, factors, field, free layer, high damping, high-speed, hypothesis, impact, influence, junction, junction devices, layer, layered materials, logic, low-power, magnetic memory, magnetic tunnel junction devices, magnetic tunnel junctions, magnetization, magneto-optical Kerr effect technique, magnetoresistance ratio, materials, memory, optical stimuli, performance, potential, process, range, ratio, response, saturation, saturation magnetization, signal, signal processing, spin-transfer torque, spintronic applications, stack, stimuli, study, technique, thickness, time-resolved magneto-optical Kerr effect technique, torque, tunnel, tunnel junction devices, tunnel junctions, tunnel magnetoresistance ratio

Funders

  • European Commission

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