Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces

Ajejas, Fernando; Anadón, Alberto; Gudín, Adrián; Díez, José Manuel Olivares; G., Ayani, Cosme; Olleros-Rodríguez, Pablo; Costa, Leticia de Melo; Navío, Cristina; Gutiérrez, Alejandro; Calleja, F.; Parga, Amadeo L. Vázquez de; Miranda, Rodolfo; Camarero, Julio; Perna, Paolo

doi:10.1021/acsami.9b19159

Cited by 14 publications

(42 citation statements)

References 41 publications

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“…laterally expanded to adjust to the lattice parameter of the substrate. The presence of Co underneath graphene is verified by XPS, as demonstrated elsewhere 17 Angular dependence XMCD measurements performed at room temperature (RT) in Gr/Co n /HM heterostructures confirm qualitatively the aforementioned polar-MOKE observations. The comparison between the dichroism spectra acquired in normal incidence (NI) and grazing incidence (GI) geometries for the different Co thicknesses directly shows: i) PMA for n < n C (i.e., larger NI dichroism signal, as Fig.…”

Section: Resultssupporting

confidence: 76%

“…1. The intercalated Co films are atomically flat as revealed by STM 17 . The LEED patterns observed after intercalation (Fig.…”

Section: Resultsmentioning

confidence: 95%

“…Among all of them, a three-dimensional morphology rapidly cancels interfacial effects in thin ferromagnetic films. Recently, a new technique 16,17 has been developed to grow high quality Co(111)/Pt(111) heterostructures by intercalation of Co atoms in Gr/Pt(111) systems, with graphene playing the role of a surfactant, a similar behaviour as in intercalation on a Ir(111) buffer [18][19][20][21] . The result is an atomically flat film of highly perfect, pseudomorphic Co in a face centered tetragonal (f ct) crystalline structure, laterally expanded to adjust to the lattice parameter of Pt, which keeps a giant PMA for unusually large thickness of the nanometer-thick Co film 16 .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Origin of the Large Perpendicular Magnetic Anisotropy in Nanometer-thick Epitaxial Graphene/Co/Heavy Metal Heterostructures

Blanco-Rey¹,

Perna²,

Gudín³

et al. 2020

Preprint

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A combination of theoretical modelling and experiments reveals the origin of the large perpendicular magnetic anisotropy (PMA) that appears in nanometer-thick epitaxial Co films intercalated between graphene (Gr) and a heavy metal (HM) substrate, as a function of the Co thickness.High quality epitaxial Gr/Co n /HM(111) (HM=Pt,Ir) heterostructures are grown by intercalation below graphene, which acts as a surfactant that kinetically stabilizes the pseudomorphic growth of highly perfect Co face-centered tetragonal (f ct) films, with a reduced number of stacking faults as the only structural defect observable by high resolution scanning transmission electron microscopy (HR-STEM). Magneto-optic Kerr effect (MOKE) measurements show that such heterostructures present PMA up to large Co critical thicknesses of about 4 nm (20 ML) and 2 nm (10 ML) for Pt and Ir substrates, respectively, while X-ray magnetic circular dichroism (XMCD) measurements show an inverse power law of the anistropy of the orbital moment with Co thickness, reflecting its interfacial nature, that changes sign at about the same critical values. First principles calculations show that, regardless of the presence of graphene, ideal Co f ct films on HM buffers do not sustain PMAs beyond around 6 MLs due to the in-plane contribution of the inner bulk-like Co layers. The large experimental critical thicknesses sustaining PMA can only be retrieved by the inclusion of structural defects that promote a local hcp stacking such as twin boundaries or stacking faults.Remarkably, a layer resolved analysis of the orbital momentum anisotropy reproduces its interfacial nature, and reveals that the Gr/Co interface contribution is comparable to that of the Co/Pt(Ir).

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Section: Resultssupporting

confidence: 76%

“…1. The intercalated Co films are atomically flat as revealed by STM 17 . The LEED patterns observed after intercalation (Fig.…”

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Origin of the Large Perpendicular Magnetic Anisotropy in Nanometer-thick Epitaxial Graphene/Co/Heavy Metal Heterostructures

Blanco-Rey¹,

Perna²,

Gudín³

et al. 2020

Preprint

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“…We investigate next the influence on the DMI of the Co stacking, known to be a key factor to explain the magnetocrystalline anisotropy of Gr/Co/Pt heterostructures. When Co is pseudomorphically grown by intercalation in Gr/Pt(111), it results in a f ct stacking rather than hcp [26,48], with stacking defects scattered through- out, nucleating predominantly near the Pt(111) substrate steps [35]. In a perfect f ct heterostructure, DFT calculations show that the magnetocrystalline anisotropy energy (MAE) follows a bulk-like behaviour with in-plane anisotropy starting at n Co = 8 (0.09 meV per Co atom, imposed by the lateral f ct lattice strain) and the critical thickness for perpendicular to in-plane switching at n c Co = 4.…”

Section: A Additivity Of Interfacial Dmimentioning

confidence: 99%

Nature of Interfacial Dzyaloshinskii-Moriya Interactions in Graphene/Co/Pt(111) Multilayer Heterostructures

Blanco-Rey,

Bihlmayer,

Arnau

et al. 2021

Preprint

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“…Fig. 8 (Ajejas et al, 2018(Ajejas et al, , 2020 and will be discussed in more depth in future work. PEEM at the Nanospectroscopy beamline of the Elettra synchrotron.…”

Section: Magnetism In Graphene/co/re(0001)mentioning

confidence: 99%

A UHV MOKE magnetometer complementing XMCD-PEEM at the Elettra Synchrotron

Genuzio¹,

Giela²,

Lucian³

et al. 2021

J Synchrotron Radiat

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We report on a custom-built UHV-compatible Magneto-Optical Kerr Effect (MOKE) magnetometer for applications in surface and materials sciences, operating in tandem with the PhotoEmission Electron Microscope (PEEM) endstation at the Nanospectroscopy beamline of the Elettra synchrotron. The magnetometer features a liquid-nitrogen-cooled electromagnet that is fully compatible with UHV operation and produces magnetic fields up to about 140 mT at the sample. Longitudinal and polar MOKE measurement geometries are realized. The magneto-optical detection is based on polarization analysis using a photoelastic modulator. The sample manipulation system is fully compatible with that of the PEEM, making it possible to exchange samples with the beamline endstation, where complementary X-ray imaging and spectroscopy techniques are available. The magnetometer performance is illustrated by experiments on cobalt ultra-thin films, demonstrating close to monolayer sensitivity. The advantages of combining in situ growth, X-ray Magnetic Circular Dichroism imaging (XMCD-PEEM) and MOKE magnetometry into a versatile multitechnique facility are highlighted.

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Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces

Abstract: arXiv:1911.07549 [cond-mat.mtrl-sci] arXiv:1911.07549 [cond-mat.mtrl-sci]

Cited by 14 publications

References 41 publications

Origin of the Large Perpendicular Magnetic Anisotropy in Nanometer-thick Epitaxial Graphene/Co/Heavy Metal Heterostructures

Origin of the Large Perpendicular Magnetic Anisotropy in Nanometer-thick Epitaxial Graphene/Co/Heavy Metal Heterostructures

Nature of Interfacial Dzyaloshinskii-Moriya Interactions in Graphene/Co/Pt(111) Multilayer Heterostructures

A UHV MOKE magnetometer complementing XMCD-PEEM at the Elettra Synchrotron

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