Magnetic anisotropy in surface-supported single-ion lanthanide complexes

Stoll, P.; Bernien, Matthias; Rolf, Daniela; Nickel, F.; Xu, Qingyu; Hartmann, Claudia; Umbach, Tobias Reinhard; Kopprasch, Jens; Ladenthin, Janina N.; Schierle, E.; Weschke, E.; Czekelius, Constantin; Kuch, W.; Franke, Katharina J.

doi:10.1103/physrevb.94.224426

Cited by 11 publications

(13 citation statements)

References 48 publications

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“…The inverted orientation indicates that for Dy‐TDA networks the effective CF acting on the Dy atoms does not follow the coordination symmetry axis. A further comparison with Dy 3+ ions in the dysprosium‐tris(1,1,1‐trifluoro‐4‐(2‐thienyl)‐2,4‐butanedionate) (Dy(tta) 3 ) complex on Au(111) [ 10 ] also confirms that the alignment of the Dy 4f orbitals in the Dy‐TDA network is close to the surface plane (see the Experimental Section for more details).…”

Section: Resultsmentioning

confidence: 79%

“…On the other side, in the work of Stoll et al. [ 10 ] it is defined as

(μ_{25 °} - μ_{90 °})

; considering that μ θ = [cos (θ)] 2 ·μ V + [sin (θ)] 2 ·μ H (see supplementary note 6 of ref. [ 44 ] ), this implies that

(μ_{25 °} - μ_{90 °}) = 0.18 \cdot (μ_{H} - μ_{V})

.…”

Section: Methodsmentioning

confidence: 99%

“…To account for random azimuthal orientations of the structures on the surface, we perform an azimuthal averaging over all orientations of the easy axis rotated around the surface normal for the same polar angle theta. Details of the procedure are described in reference [ 10 ] .…”

Section: Methodsmentioning

confidence: 99%

“…In 4f elements, the spin–orbit coupling (SOC) is larger than the crystal field (CF), which might result in higher anisotropies. [ 8,9 ] Furthermore, the CF acts as a perturbation of the SOC and can be tailored to increase the anisotropy by choosing an appropriate coordination environment, [ 7,10 ] though so far such finding has not been demonstrated for surface‐confined metal–organic networks embedding lanthanides.…”

Section: Introductionmentioning

confidence: 99%

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Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal–Organic Coordination

Parreiras

Moreno

Cirera

et al. 2021

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Taming the magnetic anisotropy of lanthanides through coordination environments is crucial to take advantage of the lanthanides properties in thermally robust nanomaterials. In this work, the electronic and magnetic properties of Dy‐carboxylate metal–organic networks on Cu(111) based on an eightfold coordination between Dy and ditopic linkers are inspected. This surface science study based on scanning probe microscopy and X‐ray magnetic circular dichroism, complemented with density functional theory and multiplet calculations, reveals that the magnetic anisotropy landscape of the system is complex. Surface‐supported metal–organic coordination is able to induce a change in the orientation of the easy magnetization axis of the Dy coordinative centers as compared to isolated Dy atoms and Dy clusters, and significantly increases the magnetic anisotropy. Surprisingly, Dy atoms coordinated in the metallosupramolecular networks display a nearly in‐plane easy magnetization axis despite the out‐of‐plane symmetry axis of the coordinative molecular lattice. Multiplet calculations highlight the decisive role of the metal–organic coordination, revealing that the tilted orientation is the result of a very delicate balance between the interaction of Dy with O atoms and the precise geometry of the crystal field. This study opens new avenues to tailor the magnetic anisotropy and magnetic moments of lanthanide elements on surfaces.

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Section: Resultsmentioning

confidence: 79%

“…On the other side, in the work of Stoll et al. [ 10 ] it is defined as

(μ_{25 °} - μ_{90 °})

; considering that μ θ = [cos (θ)] 2 ·μ V + [sin (θ)] 2 ·μ H (see supplementary note 6 of ref. [ 44 ] ), this implies that

(μ_{25 °} - μ_{90 °}) = 0.18 \cdot (μ_{H} - μ_{V})

.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal–Organic Coordination

Parreiras

Moreno

Cirera

et al. 2021

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“…In magnetic systems with easy-axis magnetic anisotropy, two magnetic states with opposite magnetic moments are separated by an energy barrier and may have long magnetic relaxation times. , For the ultimate goal to realize high-density data storage and quantum computation using single atoms or molecules, − there is an ongoing pursuit of single magnetic atoms and molecules with large easy-axis magnetic anisotropy. − For most magnetic atoms adsorbed on metal substrates, their magnetic moments are easily screened or even quenched by itinerant electrons, , while only rare cases show magnetic anisotropy energy of no more than 10 meV on Pt(111) surface. − To achieve large magnetic anisotropy, an insulating layer was used to decouple the magnetic atoms from metal substrates, whereas this strategy requires the system to be prepared and kept at low temperature. ,− In organometallic complexes, the molecular ligands provide an alternative way to decouple magnetic atoms from metal substrates. , Moreover, the ligand field surrounding the magnetic atom can determine its spin and orbital degrees of freedom and thus dictates its magnetic anisotropy by spin-orbit coupling. , In this scenario, a ligand field that can keep the magnetic atom in high-spin state and preserve its orbital angular momentum is highly desired . Until now, although various surface-adsorbed organometallic complexes were reported to show magnetic anisotropy energy in the order of several millielectronvolts, − organometallic complexes with easy-axis magnetic anisotropy have been rarely addressed. , It still remains a challenge to realize large easy-axis magnetic anisotropy in organometallic complexes.…”

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confidence: 99%

An Iron-Porphyrin Complex with Large Easy-Axis Magnetic Anisotropy on Metal Substrate

Liu

Guan

et al. 2017

ACS Nano

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Easy-axis magnetic anisotropy separates two magnetic states with opposite magnetic moments, and single magnetic atoms and molecules with large easy-axis magnetic anisotropy are highly desired for future applications in high-density data storage and quantum computation. By tuning the metalation reaction between tetra-pyridyl-porphyrin molecules and Fe atoms, we have stabilized the so-called initial complex, an intermediate state of the reaction, on Au(111) substrate, and investigated the magnetic property of this complex at a single-molecule level by low-temperature scanning tunneling microscopy and spectroscopy. As revealed by inelastic electron tunneling spectroscopy in magnetic field, this Fe-porphyrin complex has magnetic anisotropy energy of more than 15 meV with its easy-axis perpendicular to the molecular plane. Two magnetic states with opposite spin directions are discriminated by the dependence of spin-flip excitation energy on magnetic field and are found to have long spin lifetimes. Our density functional theory calculations reveal that the Fe atom in this complex, decoupled from Au substrate by a weak ligand field with elongated Fe-N bonds, has a high-spin state S = 2 and a large orbital angular momentum L = 2, which give rise to easy-axis anisotropy perpendicular to the molecular plane and large magnetic anisotropy energy by spin-orbit coupling. Since the Fe atom is protected by the molecular ligand, the complex can be processed at room or even higher temperatures. The reported system may have potential applications in nonvolatile data storage, and our work demonstrates on-surface metalation reactions can be utilized to synthesize organometallic complexes with large magnetic anisotropy.

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Imaging the Single‐Electron Ln–Ln Bonding Orbital in a Dimetallofullerene Molecular Magnet

Paschke

Birk

Avdoshenko

et al. 2021

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based complexes emerged, showing high magnetic blocking temperatures, often combined with a sufficient redox stability. [16][17][18] Recent experiments aiming at the investigation of electron transport through individual SMMs involving its magnetic system showed, however, that at least in Ln-based double-decker SMMs 4f-electrons are generally difficult to access owing to their spatial localization and energetic position far away from the Fermi level. [19][20][21][22][23][24][25] Direct addressing of 4f magnetic moments inside molecules via electronic transport would thus require systems with electronic orbitals at feasible energies combined with a certain spatial extend as can be realized for early Ln species [25] or systems with electron states that strongly hybridize with 4f orbitals without altering the peculiar magnetic properties of the magnetic complexes. [26,27] Particularly interesting in this sense are functionalized endohedral dimetallofullerenes incorporating a single-electron bond between two ferromagnetically coupled Ln atoms and representing one of the most promising classes of SMMs at the moment. [28] However, whereas their carbon cage fully absorbs the charge redistribution upon surface deposition, being beneficial for their magnetic stability, [29] their endohedral structure at the same time hinders direct access to the molecular interior, being inevitable in terms of applications. Consequently, no experimental proof has been reported up to now that demonstrates access to their magnetic core in transport measurements.In this work, we focus on the endohedral dimetallofullerene complexes Ln 2 @C 80 (CH 2 Ph), referred to as {Ln 2 } in the following. [30] These molecules consist of a roughly spherical fullerene cage that encapsulates two Ln 3+ ions, see Figure 1a. The two lanthanide ions share a single-electron covalent bond, which is stabilized by adding a CH 2 Ph side group to the C 80 cage. This metal-metal bond results in a strong exchange between the Ln centers in the [Ln 3+ -e -Ln 3+ ] system resulting in exceptional magnetic properties both in the bulk [28] and in sub-monolayers. [31,32] Liu et al. [33] have shown that the Ln-Ln bonding molecular orbital (MO) is split into two components, which are fully spin-polarized and energetically well-separated, with the unoccupied component lying below the cage-based lowest unoccupied MO (LUMO) and being partially localized on the C 80 cage thus being in principle addressable in scanning tunneling microscopy/spectroscopy (STM/STS). A decrease in Chemically robust single-molecule magnets (SMMs) with sufficiently high blocking temperatures T B are among the key building blocks for the realization of molecular spintronic or quantum computing devices. Such device applications require access to the magnetic system of a SMM molecule by means of electronic transport, which primarily depends on the interaction of magnetic orbitals with the electronic states of the metallic electrodes. Scanning tunneling microscopy in combination with ab initio calculations al...

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Magnetic anisotropy in surface-supported single-ion lanthanide complexes

Cited by 11 publications

References 48 publications

Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal–Organic Coordination

Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal–Organic Coordination

An Iron-Porphyrin Complex with Large Easy-Axis Magnetic Anisotropy on Metal Substrate

Imaging the Single‐Electron Ln–Ln Bonding Orbital in a Dimetallofullerene Molecular Magnet

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