AIP Advances (May 2017)

Perpendicular magnetic anisotropy of CoFeB\Ta bilayers on ALD HfO2

  • Bart F. Vermeulen,
  • Jackson Wu,
  • Johan Swerts,
  • Sebastien Couet,
  • Iuliana P. Radu,
  • Guido Groeseneken,
  • Christophe Detavernier,
  • Johanna K. Jochum,
  • Margriet Van Bael,
  • Kristiaan Temst,
  • Amit Shukla,
  • Shinji Miwa,
  • Yoshishige Suzuki,
  • Koen Martens

DOI
https://doi.org/10.1063/1.4978007
Journal volume & issue
Vol. 7, no. 5
pp. 055933 – 055933-6

Abstract

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Perpendicular magnetic anisotropy (PMA) is an essential condition for CoFe thin films used in magnetic random access memories. Until recently, interfacial PMA was mainly known to occur in materials stacks with MgO\CoFe(B) interfaces or using an adjacent crystalline heavy metal film. Here, PMA is reported in a CoFeB\Ta bilayer deposited on amorphous high-κ dielectric (relative permittivity κ=20) HfO2, grown by atomic layer deposition (ALD). PMA with interfacial anisotropy energy Ki up to 0.49 mJ/m2 appears after annealing the stacks between 200°C and 350°C, as shown with vibrating sample magnetometry. Transmission electron microscopy shows that the decrease of PMA starting from 350°C coincides with the onset of interdiffusion in the materials. High-κ dielectrics are potential enablers for giant voltage control of magnetic anisotropy (VCMA). The absence of VCMA in these experiments is ascribed to a 0.6 nm thick magnetic dead layer between HfO2 and CoFeB. The results show PMA can be easily obtained on ALD high-κ dielectrics.