Intrinsic orbital and spin magnetism in Rh clusters on inert xenon matrices

Sessi, Violetta; Kuhnke, Klaus; Zhang, J.; Honolka, Jan; Kern, Klaus; Tieg, C.; Šipr, O.; Minář, J.; Ebert, H.

doi:10.1103/physrevb.82.184413

Cited by 20 publications

(25 citation statements)

References 23 publications

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“…Therefore, the effective spin moment evaluated from the XMCD signal is the true magnetic spin moment. Notice that the Rh absorption spectra present in addition to the M 2 and M 3 edges a feature at 503 eV that has been reported before [29,30]. In contrast to these references, we observe a small dichroic signal also for this peak.…”

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confidence: 51%

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

et al. 2013

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In sharp contrast to previous studies on FeRh bulk, thin films, and nanoparticles, we report the persistence of ferromagnetic order down to 3 K for size-selected 3.3 nm diameter nanocrystals embedded into an amorphous carbon matrix. The annealed nanoparticles have a B2 structure with alternating atomic Fe and Rh layers. X-ray magnetic dichroism and superconducting quantum interference device measurements demonstrate ferromagnetic alignment of the Fe and Rh magnetic moments of 3 and 1 B , respectively. The ferromagnetic order is ascribed to the finite-size induced structural relaxation observed in extended x-ray absorption spectroscopy. DOI: 10.1103/PhysRevLett.110.087207 PACS numbers: 75.30.Kz, 75.75.Cd, 81.07.Bc Iron-rhodium alloys exhibit competing ferromagnetic (FM) and antiferromagnetic (AFM) phases with transition temperatures close to ambient for nearly equiatomic composition and body-centered-cubic (bcc) CsCl-like B2 structure. The competition between the two magnetic orders of FeRh holds great potential in spintronics and heat assisted magnetic recording [1,2]. Moreover, the peculiar bulk FeRh magnetic phase diagram enables its use as active material in heat pumps and refrigerators [3][4][5].At ambient conditions, bulk B2 FeRh is a G-type AFM with a total magnetic moment on the iron atoms of 3:3 B and no appreciable moment on the rhodium atoms [6][7][8]. Above the transition temperature of 370 K, the atomic moments of Fe and Rh are ferromagnetically aligned and take on total values of 3.2 and 0:9 B , respectively [6][7][8]. While it has long been known that the bcc unit cell volume expands by % 1% upon transforming to FM order [9], recent experiments suggest that distortions of the bcc structure may occur [10]. Given the itinerant character of the 3d electrons, the coupling between crystallographic and magnetic order in this system is both rich and very delicate as demonstrated by the theoretical challenge to model the system [11], as well as by recent pump-probe experiments focusing on ultrafast magnetization control [12].Finite-size systems of this alloy have received particular attention by their potential to stabilize the FM phase at room temperature and below. Strained thin films [13,14] showed traces of a FM phase down to 300 K, while ab initio calculations predicted FM down to 0 K for a Rh-terminated 9 ML FeRh(001) film [15] and for 8-atom FeRh clusters [16]. Indeed, since nanosized crystals may present significantly different interatomic distances and unit cell distortions with respect to bulk [17,18], a fundamentally modified magnetic phase diagram can be expected for FeRh nanocrystals. However, the first experiments on chemically synthesized FeRh nanoparticles (NPs) failed to evidence low temperature stability of the FM phase. Most notably, they raised important questions, such as partial B2 ordering, elemental segregation, and coalescence upon annealing [19][20][21].In this Letter, we demonstrate the persistence of FM order down to below 3 K in size-selected FeRh nanocrystals with a mean d...

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confidence: 51%

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

et al. 2013

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“…This suggests that a narrow size distribution of clusters grown on GR could provide the first observation of a non-zero total magnetic moment for surface-supported Rh clusters, with important consequences with respect to the magnetic anisotropy and the definition of a preferential axis of magnetization. In fact, previous findings of a magnetic signal were obtained on free Rh clusters 46 and on Rh clusters embedded in inert xenon, 29 that is, in both cases for clusters in isotropic environments.…”

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confidence: 98%

“…Recent experiments have indeed shown that 20 atom clusters embedded in inert xenon present total magnetic moments as large as 0.4 μ B . 29 …”

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confidence: 99%

Local Electronic Structure and Density of Edge and Facet Atoms at Rh Nanoclusters Self-Assembled on a Graphene Template

et al. 2012

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T he interest in developing novel materials using building blocks with sizes of about 1 nm has motivated the huge effort devoted to understand the properties of nanoclusters. Several studies have clearly demonstrated that atomic aggregates in the nanometer size range, that is, formed by dozens or hundreds of atoms, present remarkably different properties with respect to their bulk crystalline counterparts. Heterogeneous catalysis, energy conversion, and magnetic data storage are among the technologically most relevant fields where supported nanoclusters are expected to have a strong impact. 1,2 An important field for application of the new nanocluster-based materials is catalysis. The most striking example is the high chemical activity of small Au nanoclusters, 3À6 given by highly reactive corner and edge atoms with low coordination number C N , but even other transition metals like Pt present nanoclusters with a similar behavior. 7,8 One of the goals of nanotechnology is the manipulation of the magnetic properties in systems with reduced dimensionality, such as quantum wires, quantum dots, and nanoclusters. As an example, the use of nanoclusters for ultrahigh density magnetic recording requires pushing further away the superparamagnetic limit by enhancing the magnetic anisotropy energy. In this respect, experiments have shown that low C N atoms play a pivotal role. 9,10 When the particle's size is reduced to only 10À20 Å, two main challenges are posed: (i) the formation in a controllable and reproducible manner of large-scale replicas of these individual building blocks on a suitable substrate 11 and (ii) the determination and tuning of the geometric and electronic structure of the supported nanoobjects.One of the most recent solutions to meet the first challenge is to make use of template graphene (GR) for the growth of metallic nanoclusters and for the formation of long-range-ordered superstructures. This * Address correspondence to alessandro.baraldi@elettra.trieste.it.Received for review November 24, 2011 and accepted March 9, 2012. Published online 10.1021/nn300651s ABSTRACTThe chemical and physical properties of nanoclusters largely depend on their sizes and shapes. This is partly due to finite size effects influencing the local electronic structure of the nanocluster atoms which are located on the nanofacets and on their edges. Here we present a thorough study on graphene-supported Rh nanocluster assemblies and their geometrydependent electronic structure obtained by combining high-energy resolution core level photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory. We demonstrate the possibility to finely control the morphology and the degree of structural order of Rh clusters grown in register with the template surface of graphene/Ir(111). By comparing measured and calculated core electron binding energies, we identify edge, facet, and bulk atoms of the nanoclusters. We describe how small interatomic distance changes occur while varying the nanocluster size, substantia...

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“…Rhodium stands out because it is located at the center of the periodic table with an unfilled 4d shell, which produces rich physical and chemical properties. Rhodium clusters have been intensively studied by using theoretical methods [1][2][3][4][5][6] to understand their catalytic properties and the emergence of the electronic and magnetic properties [7][8][9][10]. Small rhodium clusters were found to possess magnetic moments [11,12] on the order of one Bohr magneton (1μ B ) per atom, making this the only 4d element with magnetic order at the nanoscale and with Mn [13] the only known elements that are magnetic at nanoscale but not in the bulk.…”

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confidence: 98%

Multiferroic Rhodium Clusters

Moro

Bowlan

et al. 2014

Phys. Rev. Lett.

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Simultaneous magnetic and electric deflection measurements of rhodium clusters (Rh(N), 6 ≤ N ≤ 40) reveal ferromagnetism and ferroelectricity at low temperatures, while neither property exists in the bulk metal. Temperature-independent magnetic moments (up to 1 μ(B) per atom) are observed, and superparamagnetic blocking temperatures up to 20 K. Ferroelectric dipole moments on the order of 1D with transition temperatures up to 30 K are observed. Ferromagnetism and ferroelectricity coexist in rhodium clusters in the measured size range, with size-dependent variations in the transition temperatures that tend to be anticorrelated in the range n = 6-25. Both effects diminish with size and essentially vanish at N = 40. The ferroelectric properties suggest a Jahn-Teller ground state. These experiments represent the first example of multiferroic behavior in pure metal clusters.

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Intrinsic orbital and spin magnetism in Rh clusters on inert xenon matrices

Cited by 20 publications

References 23 publications

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Local Electronic Structure and Density of Edge and Facet Atoms at Rh Nanoclusters Self-Assembled on a Graphene Template

Multiferroic Rhodium Clusters

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