Structural, vibrational, and magnetic properties of self-assembled CoPt nanoalloys embedded in SrTiO 3

M. Hennes (1) , E. Fonda (2) , N. Casaretto (1) , J. Buchwald (3) , X. Weng (1) , G. Patriarche (4) , D. Demaille (1) , Y. Zheng (1) , F. Vidal (1)

1 INSP-E8 - Croissance et propriétés de systèmes hybrides en couches minces
2 SSOLEIL - Synchrotron SOLEIL
3 Institute for Materials Science [Dresden]
4 C2N - Centre de Nanosciences et de Nanotechnologies

Pulsed laser deposition was used to synthesize vertically aligned nanocomposites (VAN), consisting of ultrathin CoPt nanocolumns embedded in a single crystal SrTiO3 thin film. Combining highresolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS) and molecular dynamics (MD) simulations, we provide an in-depth analysis of the structural and vibrational properties of the CoPt phase over a wide range of concentrations. Despite growing the samples at high temperatures (> 600 • C), we find that the CoPt nanoalloys are characterized by a high degree of structural disorder and complete absence of chemical ordering, even after additional sample annealing. Unexpectedly, for a Co concentration exceeding c(Co) 0.55, pole figure measurements unravel a transition from a highly textured short range disordered fcc phase to a disordered hcp phase with c-axis oriented out of plane. These findings, further confirmed by magnetometry measurements, illustrate the profound impact of vertical epitaxy on the structural and thermodynamic properties of bimetallic CoPt alloys.

Domaines: Physique [physics]

M. Hennes, E. Fonda, N. Casaretto, J. Buchwald, X. Weng, et al.. Structural, vibrational, and magnetic properties of self-assembled CoPt nanoalloys embedded in SrTiO 3. Physical Review Materials, 2020, 4 (12), ⟨10.1103/PhysRevMaterials.4.126001⟩. ⟨hal-03095549⟩