Direct Observation of Ferromagnetic Spin Polarization in Gold Nanoparticles

Yamamoto, Yoshiyuki; Miura, Takahiro; Teranishi, Toshiharu; Miyake, Mikio; Hori, Hidenobu; Suzuki, Motohiro; Kawamura, N.; Miyagawa, Hayato; Nakamura, Tetsuya; Kobayashi, K.

doi:10.1103/physrevlett.93.116801

Cited by 303 publications

(137 citation statements)

References 31 publications

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“…X-ray magnetic circular dichroism (XMCD) can be used to determine, with element specificity, the spin and orbital contributions to the moment. Even very small magnetic moments, such as obtained in Au for the case of multilayers, nanoparticles and intermetallic alloys, can be measured with high precision [10][11][12] . Thus, XMCD is highly suitable to obtain information on the validity of Hund's third rule.…”

Section: Introductionmentioning

confidence: 99%

Violation of Hund's third rule in structurally disordered ferromagnets

et al. 2011

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Violation of Hund's third rule caused by structural disorder is observed for the induced magnetic moment of Zr, using X-ray magnetic circular dischroism. The induced spin and orbital magnetic moments are anti-parallel in the crystalline state, but parallel in an amorphous state of the investigated Co-and Fe-based materials. First principles calculations are used to provide physical insight into the dependency of the spin-orbit coupling on the interatomic distance and coordination number.

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Section: Introductionmentioning

confidence: 99%

Violation of Hund's third rule in structurally disordered ferromagnets

et al. 2011

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“…We use this technique to probe two Sc-C 60 and Cu-C 60 samples whose structure includes a thin Sc film of 2 nm (2.5 nm for Cu-C 60 ) and a thick Sc film of 5 nm (15 nm for Cu-C 60 ). Nanoscaling of nonmagnetic metals has been shown to give rise to spin ordering (30)(31)(32)(33). The thin films should give rise to a strong magnetic signal, whereas for the thicker films, the interfacial magnetization should be quenched or diluted by the bulk properties of the metal.…”

Section: Systemmentioning

confidence: 99%

Emergent magnetism at transition-metal–nanocarbon interfaces

Ma’Mari

Rogers

Alghamdi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Charge transfer at metallo-molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc-C 60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo-carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp 3 orbitals are annealed into sp 2 −π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C 60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz-π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices. emergent magnetism | molecular spintronics | interfacial magnetism | charge transfer | nanocarbon I nterfaces are critical in quantum physics, and therefore we must explore the potential for designer hybrid materials that profit from promising combinatory effects. In particular, the fine-tuning of spin polarization at metallo-organic interfaces opens a realm of possibilities, from the direct applications in molecular spintronics and thin-film magnetism to biomedical imaging or quantum computing. This interaction at the surface can control the spin polarization in magnetic field sensors, generate magnetization spin-filtering effects in nonmagnetic electrodes, or even give rise to a spontaneous spin ordering in nonmagnetic elements such as diamagnetic copper and paramagnetic manganese (1-11).The impact of carbon-based molecules on adjacent ferromagnets is not limited to spin filtering and electronic transport, but extends to induced changes in the metal anisotropy, magnetization, coercivity, and bias (12-14). Charge transfer and d(metal)-π(carbon) orbital coupling at the interface may change the density of states, spin population, and exchange of metallocarbon interfaces (4,15,16). The interaction between the molecule and the metal depends strongly on the morphology and specific molecular geometry (17, 18). It may lead to a change in the density of states at the Fermi energy DOS(E F ) and/or the exchange-correlation integral (I s ) as described by the Stoner criterion for ferr...

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“…Despite all the efforts in this field, the permanent magnetism shown by these systems is not yet understood (Vager and Naaman, 2004;Hernando and García, 2006;Hernando et al, 2006a;Crespo et al, 2006). On this matter, studies regarding the origins of the ferromagnetic-like behaviour (Yamamoto et al, 2004;Negishi et al, 2006) were performed by means of x-ray magnetic circular dichroism (XMCD); unfortunately, in spite of having two research works trying to discern the origins of such a particular magnetic behaviour, the reason behind it still remains unclear. Recently, a set of new experiments was performed in our research group that studied the influence of the particle diameter in the magnetic behaviour of thiol-capped gold NPs (Guerrero et al, 2007).…”

mentioning

confidence: 99%

Electronic structure, magnetic properties, and microstructural analysis of thiol-functionalized Au nanoparticles: role of chemical and structural parameters in the ferromagnetic behaviour

et al. 2008

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Gold nanoparticles (NPs) have been stabilized with a variety of thiol-containing molecules in order to change their chemical and physical properties; among the possible capping systems, alkane chains with different lengths, a carboxylic acid and a thiol-containing biomolecule (tiopronin) have been selected as protecting shells for the synthesized NPs; the NPs solubility in water or organic solvents is determined by the protecting molecule. A full microstructural characterization of these NPs is presented in the current research work. It has been shown that NPs capped with alkanethiol chains have a marked ferromagnetic behaviour which might be also dependent on the chain length. The simultaneous presence of Au-Au and Au-S bonds together with a reduced particle diameter, and the formation of an ordered monolayer protective shell, have been proved to be key parameters for the ferromagnetic-like behaviour exhibited by thiol-functionalized gold NPs.

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Direct Observation of Ferromagnetic Spin Polarization in Gold Nanoparticles

Cited by 303 publications

References 31 publications

Violation of Hund's third rule in structurally disordered ferromagnets

Violation of Hund's third rule in structurally disordered ferromagnets

Emergent magnetism at transition-metal–nanocarbon interfaces

Electronic structure, magnetic properties, and microstructural analysis of thiol-functionalized Au nanoparticles: role of chemical and structural parameters in the ferromagnetic behaviour

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