Effect of heavy metal layer thickness on spin-orbit torque and current-induced switching in Hf broken vertical bar CoFeB broken vertical bar MgO structures


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Akyol M. , Jiang W., Yu G., Fan Y., Güneş M., EKİCİBİL A. , ...More

APPLIED PHYSICS LETTERS, vol.109, no.2, 2016 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 109 Issue: 2
  • Publication Date: 2016
  • Doi Number: 10.1063/1.4958295
  • Title of Journal : APPLIED PHYSICS LETTERS

Abstract

We study the heavy metal layer thickness dependence of the current-induced spin-orbit torque (SOT) in perpendicularly magnetized Hf broken vertical bar CoFeB broken vertical bar MgO multilayer structures. The damping-like (DL) current-induced SOT is determined by vector anomalous Hall effect measurements. A non-monotonic behavior in the DL-SOT is found as a function of the thickness of the heavy-metal layer. The sign of the DL-SOT changes with increasing the thickness of the Hf layer in the trilayer structure. As a result, in the current-driven magnetization switching, the preferred direction of switching for a given current direction changes when the Hf thickness is increased above similar to 7 nm. Although there might be a couple of reasons for this unexpected behavior in DL-SOT, such as the roughness in the interfaces and/or impurity based electric potential in the heavy metal, one can deduce a roughness dependence sign reversal in DL-SOT in our trilayer structure. Published by AIP Publishing.