Breakdown of magnetism in sub-nanometric Ni clusters embedded in Ag

Abstract

Downsizing to the nanoscale has opened up a spectrum of new magnetic phenomena yet to be discovered. In this context, we investigate the magnetic properties of Ni clusters embedded in a metallic Ag matrix. Unlike in Ni free-standing clusters, where the magnetic moment increases towards the atomic value when decreasing the cluster size, we show, by tuning the Ni cluster size down to the sub-nanoscale, that there is a size limit below which the clusters become non-magnetic when embedded in Ag. To this end, we have fabricated by DC-sputtering a system composed of sub-nanometer sized and non interacting Ni clusters embedded into a Ag matrix. A thorough experimental characterization by means of structural techniques (x-ray diffraction, x-ray absorption spectroscopy) and DC-magnetization confirms that the cluster size is in the sub-nanometric range and shows that the magnetization of the system is dramatically reduced, reaching only 38% of the bulk value. The experimental system has been reproduced by density functional theory calculations on Ni m clusters (m = 1-6, 10 and 13) embedded in Ag. The combination of the experimental and theoretical analysis points out that there is a breakdown of magnetism occurring below a cluster size of six atoms. According to our results, the loss of magnetic moment is not due to Ag-Ni hybridization but to charge transfer between the Ni sp and d orbitals, and the reduced magnetization observed experimentally is explained on the basis of the presence of a narrow cluster size-distribution where magnetic and non-magnetic clusters coexist.

First principles study of bimetallic Ni13−nAgn nano-clusters (n = 0–13): Structural, mixing, electronic, and magnetic properties

“…The magnetic moments of the embedded Ni clusters not only get quenched like clusters of other 3d transition metal atoms, [76] but the Ni cluster also becomes nonmagnetic below a critical size limit. [77] The calculated magnetic moments for the MESs of the binary NiAg clusters which possess a core-shell like structural pattern with Ni atoms at the core, also indicate similar type of variation and the NiAg binary cluster indeed becomes nonmagnetic in case of the NiAg 12 cluster which is incidentally identified here as the magic cluster for the 13 atoms sized binary NiAg clusters. Starting with total magnetic moment of 9.95 µ B of pure Ni cluster, which is in accordance with the previous results, [58] the total magnetic moments of the MESs for the NiAg alloy clusters, decrease almost monotonically with the increase of Ag-content and eventually become zero for the NiAg 12 cluster, as seen from the left top panel of Fig.…”

Exploring Photothermal Pathways via in Situ Laser Heating in the Transmission Electron Microscope: Recrystallization, Grain Growth, Phase Separation, and Dewetting in Ag0.5Ni0.5 Thin Films

“…Several studies have investigated the magnetic (Kitada, 1985) and magnetoresistance properties of Ag x Ni 1− x alloys (Kubinski & Holloway, 1995) where a magnetoresistance value of ~7% was observed in gas flow condensation grown nanoparticles (Dimesso & Hahn, 1998). Furthermore, microstructural and magnetic properties of dilute nickel in silver alloys have been investigated, which revealed that clusters having fewer than six atoms have a reduced associated magnetic moment due to charge transfer between the Ni sp and d orbitals (Garcia Prieto et al, 2015). Of particular relevance to this study, the evolution of silver rich Ag x Ni 1− x films at various compositions and annealing temperatures have previously been studied (Proux et al, 1999, 2000 a , 2000 b ).…”

Atomic-scale tailoring of spin susceptibility via non-magnetic spin-orbit impurities

“…However, in the presence of generic spin-orbit couplings a more complicated relationship between spin susceptibility and the strength of the various spin-dependent interaction channels emerges 32 . It may be possible to calculate G 0 eff using ab-initio methods, similarly to e.g., the treatment of Ni clusters magnetism in Ag 33 . Alternatively, one may be able to extract G 0 eff from a Kondo lattice-like model.…”