Nanostructure-induced <i>L</i>1<sub>0</sub>-ordering of twinned single-crystals in CoPt ferromagnetic nanowires

Toyama, Ryo; Kawachi, Shiro; Yamaura, Jun‐ichi; Fujita, Takeshi; Murakami, Youichi; Hosono, Hideo; Majima, Yutaka

doi:10.1039/d2na00626j

Cited by 6 publications

(3 citation statements)

References 134 publications

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“…The lattice constant of the 500 • C-grown film is summarized in figure 2(d). The lattice constant of L1 0 -CoPt agrees with the previous reports [44][45][46][47][48]. As a result, the crystal structure of the 500 • C-grown film changed from fcc Co, A1-CoPt, L1 0 -CoPt, A1-CoPt to fcc Pt as increasing x.…”

Section: Crystal Structuressupporting

confidence: 90%

Large anomalous Nernst conductivity of L1₀-ordered CoPt in CoPt composition-spread thin films

Toyama,

Masuda,

Simalaotao

et al. 2024

J. Phys. D: Appl. Phys.

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We demonstrate a high-throughput experimental characterization of anomalous Nernst conductivity (αxy A ) of L10-ordered CoPt using Co1–x Pt x composition-spread thin films on MgO(100) substrates. The compositional dependence of the anomalous Nernst effect (ANE), anomalous Hall effect (AHE) and Seebeck effect is systematically measured. As increasing the Pt concentration, the crystal structure in the composition-spread film grown at 500 °C changes from fcc Co, A1-disordered CoPt, L10-ordered CoPt, A1-CoPt to fcc Pt. The largest αxy A of 2.52 A m–1 K–1 is obtained in L10-CoPt for Pt-rich composition of x = 70%, which is larger than that for an additionally fabricated nearly stoichiometric L10-Co48Pt52 reference uniform film. The contribution from direct conversion of a temperature gradient to a transverse charge current through αxy A is dominant to the total anomalous Nernst coefficient compared to the AHE-related contribution. From a scaling analysis of the AHE, the intrinsic contribution is found to be dominant for x = 70%. A theoretical calculation for αxy A of L10-Co50Pt50 agrees with the experimental αxy A value for the nearly stoichiometric reference film by considering on-site Coulomb interaction for Co atoms. We also point out the possible electron doping effect by the addition of Pt in L10-CoPt, which could explain the larger αxy A for the off-stoichiometric Pt-rich composition than that for the nearly stoichiometric one. Our experimental and theoretical results suggest the potential of L10-CoPt with a large αxy A originating from the intrinsic mechanism for future thermoelectric applications.

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Section: Crystal Structuressupporting

confidence: 90%

Large anomalous Nernst conductivity of L1₀-ordered CoPt in CoPt composition-spread thin films

Toyama,

Masuda,

Simalaotao

et al. 2024

J. Phys. D: Appl. Phys.

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“…While it is uncommon, one-dimensional nanowires consisting of L1 0 -PtCo core 98 and Pt-rich surface were reported. 22 This nanostructure exhibits compressively strained high-index facets.…”

Section: Morphological Controlmentioning

confidence: 99%

Design principles for the synthesis of platinum–cobalt intermetallic nanoparticles for electrocatalytic applications

Yang

2023

Chem. Commun.

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“…This is caused by different diffusion mechanisms (e.g. surface, triple junctions, grain boundaries, bulk) which can contribute simultaneously to the mass transfer, the presence of moving grain boundaries, diffusant accumulation at the free surface, near substrate region and other interfaces to name just a few [29,[39][40][41]. So far, there have been no reports on the estimation of diffusion parameters in Co/Pt-based thin-film stacks, which motivates quantitative characterization of diffusion and diffusioncontrolled phase formation in these functional materials.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature diffusion in thin-film Pt-(Au-)-Co heterostructures: a structural and magnetic characterization

Pedan,

Makushko,

Yavorskyi

et al. 2024

Nanotechnology

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Formation of functional thin films for nanoelectronics and magnetic data storage via thermally induced diffusion-driven structural phase transformations in multilayer stacks is a promising technology-relevant approach. Ferromagnetic thin films based on CoPt alloys are considered as a material science platform for the development of various applications such as spin valves, spin orbit torque devices, and high-density data storage media. Here, we study diffusion processes in Pt-Co-based stacks with the focus on the effect of layers inversion (Pt/Co/substrate vs. Co/Pt/substrate) and insertion of an intermediate Au layer on the structural transitions and magnetic properties. We demonstrate that layer stacking has a pronounced effect on the diffusion rate at temperatures, where the diffusion is dominated by grain boundaries. We quantify effective diffusion coefficients, which characterize the diffusion rate of Co and Pt through the interface and grain boundaries, providing the possibility to control the homogenization rate of Pt-Co-based heterostructures. The obtained values are in the range of 10-16 – 10-13 cm2/s for temperatures of 150 °C – 350 °C. Heat treatment of thin-film samples results in the coercivity enhancement, which is attributed to short-range chemical ordering effects. We show that introducing an additional Au intermediate layer leads to an increase of the coercive field of the annealed samples due to a modification of exchange coupling between the magnetic grains at the grain boundaries.

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Nanostructure-induced L1₀-ordering of twinned single-crystals in CoPt ferromagnetic nanowires

Abstract: L10-ordered ferromagnetic nanowires with large coercivity are essential for realizing next-generation spintronic devices. Ferromagnetic nanowires have been commonly fabricated by first L10-ordering of initially disordered ferromagnetic films by annealing and...

Cited by 6 publications

References 134 publications

Large anomalous Nernst conductivity of L1₀-ordered CoPt in CoPt composition-spread thin films

Large anomalous Nernst conductivity of L1₀-ordered CoPt in CoPt composition-spread thin films

Design principles for the synthesis of platinum–cobalt intermetallic nanoparticles for electrocatalytic applications

Low-temperature diffusion in thin-film Pt-(Au-)-Co heterostructures: a structural and magnetic characterization

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Nanostructure-induced L10-ordering of twinned single-crystals in CoPt ferromagnetic nanowires

Abstract: L10-ordered ferromagnetic nanowires with large coercivity are essential for realizing next-generation spintronic devices. Ferromagnetic nanowires have been commonly fabricated by first L10-ordering of initially disordered ferromagnetic films by annealing and...

Cited by 6 publications

References 134 publications

Large anomalous Nernst conductivity of L10-ordered CoPt in CoPt composition-spread thin films

Large anomalous Nernst conductivity of L10-ordered CoPt in CoPt composition-spread thin films

Design principles for the synthesis of platinum–cobalt intermetallic nanoparticles for electrocatalytic applications

Low-temperature diffusion in thin-film Pt-(Au-)-Co heterostructures: a structural and magnetic characterization

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Nanostructure-induced L1₀-ordering of twinned single-crystals in CoPt ferromagnetic nanowires

Large anomalous Nernst conductivity of L1₀-ordered CoPt in CoPt composition-spread thin films

Large anomalous Nernst conductivity of L1₀-ordered CoPt in CoPt composition-spread thin films