Magnetic Anisotropy of Cr<sub>7</sub>Ni Spin Clusters on Surfaces

Corradini, Valdis; Ghirri, Alberto; Garlatti, Elena; Biagi, Roberto; Renzi, Valentina De; Pennino, U. del; Bellini, V.; Carretta, S.; Santini, P.; Timco, Grigore A.; Winpenny, Richard E. P.; Affronte, Marco

doi:10.1002/adfm.201200478

Cited by 35 publications

(37 citation statements)

References 41 publications

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“…In our approach, we restrict ourselves to thermal excitations starting from the electronic ground state only, i.e., assume only one spin moment and its corresponding anisotropies. In principle thermal excitations may also populate electronic states that have different (spin) moment and anisotropies [2,30,50]. This is potentially a rather drastic simplification at the temperatures of the XMCD measurements (T = 8 K).…”

Section: The Spin Hamiltonianmentioning

confidence: 99%

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms onCu2N/Cu(100)

et al. 2015

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We report on the magnetic properties of Fe and Co adatoms on a Cu 2 N/Cu(100)-c(2 × 2) surface investigated by x-ray magnetic dichroism measurements and density functional theory (DFT) calculations including the local coulomb interaction. We compare these results with properties formerly deduced from STM spin excitation spectroscopy (SES) performed on the individual adatoms. In particular we focus on the values of the local magnetic moments determined by XMCD compared to the expectation values derived from the description of the SES data. The angular dependence of the projected magnetic moments along the magnetic field, as measured by XMCD, can be understood on the basis of the SES Hamiltonian. In agreement with DFT, the XMCD measurements show large orbital contributions to the total magnetic moment for both magnetic adatoms. Single magnetic atoms adsorbed on nonmagnetic surfaces enable fundamental insights into the origins of magnetic properties [1,2] and have the potential of long relaxation times of magnetic states that can be used for quantum information processing or storage [3,4]. To investigate such systems, x-ray magnetic circular dichroism (XMCD) is a well established technique that allows us to determine element specifically the spin (m S ), dipole (m D ), and orbital (m L ) moments and their anisotropies [5,6]. The dipole moment reflects the inhomogeneous spin density distribution within the atom which influences the transition matrix elements in the XMCD sum rules [6]. Compared to atomic dimensions XMCD is a spatially averaging technique. However, due to its high sensitivity, ensembles of individual adatoms can be probed at coverages where the adatoms are sufficiently distant from one another such that their mutual interactions become negligible [7,8].For individual atoms or molecules, spin-excitation spectroscopy (SES) with a scanning tunneling microscope (STM) enables access to magnetic properties like the gyromagnetic ratio (g) and magnetic anisotropies [2,. These studies have been made on magnetic impurities with very different degrees of hybridization with the substrate, ranging from direct contact with metals, semiconductors, and superconductors to adatoms adsorbed on thin insulating films or graphene decoupling layers. In the vast majority of cases, the SES results were discussed on the basis of an effective spin Hamiltonian * m.etzkorn@fkf.mpg.de using an atomic picture that has the form [11]:This description is well established in the field of electron spin resonance (ESR) [30,31] and molecular magnets [32] and typically used for systems where the local moments are well protected from hybridization with the conduction electrons of a metal. STM studies are naturally limited to conductive systems in which the electronic transport through the adatoms or molecules to the substrate is significant. This may alter the properties of the system and questions the use of an atomic description for its excitations motivating alternative models [18]. Nevertheless, the described spin Hamiltonian reproduces...

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Section: The Spin Hamiltonianmentioning

confidence: 99%

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms onCu2N/Cu(100)

et al. 2015

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“…36 Cr 7 Ni ring spin clusters assembled on a Au substrate have also been investigated using XMCD technique as a function of temperature and field, demonstrating that the relative orientation between the Cr and the Ni magnetic moments changes from antiparallel to parallel with increasing temperature. 37 In addition, SMM behavior has also been proven in the endohedral system DySc 2 N@C 80 with complementary XMCD and SQUID measurements. 38 The effect of ligand substitution on the interaction between the Dy ions and the Fe ions on {Fe 2 Dy 2 } clusters has been investigated by means of Mössbauer spectroscopy.…”

Section: Introductionmentioning

confidence: 96%

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(Ln
Badía-Romano
¹
,
Bartolomé
²
,
Bartolomé
³

et al. 2013
Phys. Rev. B
21
2
14
0
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The intramolecular exchange interactions within the single-molecule magnet (SMM) "butterfly" molecule [Fe 3 Ln(μ 3 -O) 2 (CCl 3 COO) 8 (H 2 O)(THF) 3 ], where Ln(III) represents a lanthanide cation, are determined in a combined experimental [x-ray magnetic circular dichroism (XMCD) and vibrating sample magnetometer (VSM)] and theoretical work. Compounds with Ln = Gd and Dy, which represent extreme cases where the rare earth presents single-ion isotropic and uniaxial anisotropy, on one hand, and with Ln = Lu and Y(III) as pseudolanthanide substitutions that supply a nonmagnetic Ln reference case, on the other hand, are studied. The Dy single-ion uniaxial anisotropy is estimated from ab initio calculations. Low-temperature (T 2.5 K) hard x-ray XMCD at the Ln L 2,3 edges and VSM measurements as a function of the field indicate that the Ln moment dominates the polarization of the molecule by the applied field. Within the {Fe 3 LnO 2 } cluster the Ln-Fe 3 subcluster interaction is determined to be antiferromagnetic in both Dy and Gd compounds, with values J Dy-Fe 3 = −0.4 K and J Gd-Fe 3 = −0.25 K, by fitting to spin Hamiltonian simulations that consider the competing effects of intracluster interactions and the external applied magnetic field. In the uniaxial anisotropic {Fe 3 DyO 2 } case, a field-induced reorientation of the Fe 3 and Dy spins from an antiparallel to a parallel orientation takes place at a threshold field (μ 0 H = 4 T). In contrast, in isotropic {Fe 3 GdO 2 } this reorientation does not occur.

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“…16 In the literature, the applicability of such rules is controversial due to some arbitrary assumptions concerning the number of 3d holes, the j -j mixing effect, and the presence of the dipolar term T z . We have already discussed the validity of the sum rules for Cr 8 , Cr 7 Ni, Cr x InNi, [17][18][19][20][21] and Cr 2 Cu. 22 In the following we discuss their applicability in the case of the Cr 2n Cu 2 molecules.…”

Section: X-ray Spectroscopiesmentioning

confidence: 99%

“…[17][18][19][20][21][22] Since the line shape of the Cr-L 2,3 absorption spectra is here very similar, for Cr 2n Cu 2 rings we use the same SC value of 1.75 ± 0.05. This choice is also supported by the very similar bond lengths and angles around each Cr ion in Cr 2n Cu 2 , as compared to the Cr 7 Ni and Cr 8 systems.…”

Section: -5mentioning

confidence: 99%

Magnetic and entanglement properties of molecular Cr2nCu2heterometallic spin rings

et al. 2012

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We investigate the low-temperature magnetic and entanglement properties of a series of molecular Cr 2n Cu 2 heterometallic spin rings (with n = 4,5,6). These are cyclic spin systems, consisting of two Cu 2+ (s = 1/2) ions, coupled by two antiferromagnetic segments of n Cr 3+ (s = 3/2) ions. Thermodynamic measurements (magnetization, susceptibility, and specific heat) allow us to determine the total spin of the ground state and to estimate the spin-Hamiltonian parameters related to magnetic anisotropy. X-ray spectroscopies (XAS and XMCD) are used to probe the local magnetization of the Cr and Cu ions, and provide results that are consistent with the bulk magnetization data. We finally investigate the relation between heterometallicity and entanglement in these prototypical spin systems. In particular, we focus on the spatial modulation of entanglement induced by the Cu defect spins and on the long-distance entanglement between them induced by the two Cr chains.

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Magnetic Anisotropy of Cr₇Ni Spin Clusters on Surfaces

Cited by 35 publications

References 41 publications

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms onCu2N/Cu(100)

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms onCu2N/Cu(100)

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(Ln
Badía-Romano
¹
,
Bartolomé
²
,
Bartolomé
³

et al. 2013
Phys. Rev. B
21
2
14
0
View full text Add to dashboard Cite

Magnetic and entanglement properties of molecular Cr2nCu2heterometallic spin rings

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Magnetic Anisotropy of Cr7Ni Spin Clusters on Surfaces

Cited by 35 publications

References 41 publications

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms onCu2N/Cu(100)

Comparing XMCD and DFT with STM spin excitation spectroscopy for Fe and Co adatoms onCu2N/Cu(100)

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(LnBadía-Romano1, Bartolomé2, Bartolomé3 et al. 2013Phys. Rev. B212140View full textAdd to dashboardCite

Magnetic and entanglement properties of molecular Cr2nCu2heterometallic spin rings

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Product

Resources

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Magnetic Anisotropy of Cr₇Ni Spin Clusters on Surfaces

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(Ln
Badía-Romano
¹
,
Bartolomé
²
,
Bartolomé
³

et al. 2013
Phys. Rev. B
21
2
14
0
View full text Add to dashboard Cite