Exotic magnetism of s-electron cluster arrays: Ferromagnetism, ferrimagnetism and antiferromagnetism

Nakano, T.; Hanh, Duong Thi; Nozue, Yasuo; Nam, Nguyễn Hoàng; Duan, Truong Cong; Araki, Shingo

doi:10.3938/jkps.63.699

Cited by 12 publications

(30 citation statements)

References 34 publications

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“…Negative Weiss temperatures have been observed [7,11]. The Curie and Weiss temperatures change with n [13,26,44], as shown in Figure 10(b). A finite optical gap has been observed in IR absorption tails [7,11], and ferromagnetic samples are assigned to Mott insulators.…”

Section: Mott Insulator and Canted Antiferromagnetism In K-loaded Zeomentioning

confidence: 72%

“…At n 1, an optical absorption band assigned to the 1s-1p optical transition in Figure 1(b) has been observed at the expected energy 1.2 eV [3]. Optical reflection spectra show a successive change with n [3], as shown in Figure 10(a) [44]. The 1s-1p band at 1.2 eV grows with n at n < 2, and shrinks with n at n > 2.…”

Section: Mott Insulator and Canted Antiferromagnetism In K-loaded Zeomentioning

confidence: 81%

“…One of the most striking results in this system is the Néel's N-type ferrimagnetism at x = 4 for 6.7 ≤ n ≤ 8 [23,37,44]. A typical temperature dependence of spontaneous magnetization at n = 7.8 is shown by red curve in Figure 5(a).…”

Section: Ferrimagnetism and Ferromagnetism In Na-k Alloy System In Zementioning

confidence: 90%

“…s-electrons of clusters in adjoining α-cages have mutual interaction through 8Rs as well as within a cluster. These aspects of alkali-metal clusters in zeolites are compared to superatoms [19,20,44] with the electronic shell structure of metal clusters [57] and their regular arrays to cluster crystals [1,26,58]. New promising material designs have been proposed based on the regular nanostructures of porous crystals.…”

Section: Introductionmentioning

confidence: 99%

“…A new paradigm of electronic system can be provided by the alkali-metal loading into zeolites. Up to now, comprehensive researches have been carried out , especially on magnetic properties [1,2,9,11,[13][14][15][16][17][18][23][24][25][26][27][28][29][30][31][34][35][36][37]39,41,[43][44][45][46]48,50,51], optical properties [1,3,7,24,38,49,53], electrical properties [42,43,49,50,52,53], structural analyses [8,12,22,47] and theoretical calculations …”

Section: Introductionmentioning

confidence: 99%

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Electrons of alkali metals in regular nanospaces of zeolites

Nakano

Nozue

2017

Advances in Physics: X

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The s-electrons of alkali metals loaded into regular nanospaces (nanocages) of zeolite crystals display novel electronic properties, such as a ferrimagnetism, a ferromagnetism, an antiferromagnetism, an insulator-to-metal transition, etc., depending on the kind of alkali metals, their loading density, and the structure type of zeolite frameworks. These properties are entirely different from those in bulk alkali metals of freeelectrons. Alkali-metal clusters are stabilized in cages of zeolites, and new quantum states of s-electrons, such as 1s, 1p, and 1d states in the spherical quantum-well model, are formed. An electron correlation, a polaron effect, and an orbital degeneracy in the quantum states of s-electrons play critical roles in taking on the novel electronic properties. Electronic properties can be overviewed systematically by a coarse-grained model of localized s-electron states in cages based on the tightbinding approximation, followed by the t-U-S-n diagram of the correlated polaron system given by the so-called HolsteinHubbard Hamiltonian: an electron transfer energy through windows of cages (t), a Coulomb repulsion energy between two s-electrons in the same cage (U), a short-range electron-phonon interaction energy due to the cation displacements (S), and an average number of s-electrons per cage (n). Beyond the jellium background model of alkali-metal clusters, a huge spin-orbit interaction has been observed in the 1p degenerate orbitals of clusters, similarly to the Rashba mechanism. ARTICLE HISTORY

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Section: Mott Insulator and Canted Antiferromagnetism In K-loaded Zeomentioning

confidence: 72%

Section: Mott Insulator and Canted Antiferromagnetism In K-loaded Zeomentioning

confidence: 81%

Section: Ferrimagnetism and Ferromagnetism In Na-k Alloy System In Zementioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrons of alkali metals in regular nanospaces of zeolites

Nakano

Nozue

2017

Advances in Physics: X

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Crystal Structures of Heavily Na-Loaded Low-Silica X (LSX) Zeolites in Insulating and Metallic States

2014

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Crystal structures of sodium clusters incorporated in LSX zeolite [Na 12 Al 12 Si 12 O 48 (Z = 8)] with FAU-type topology are analyzed by powder X-ray diffraction. The two different Na-loaded samples, Na 9.4 /Na 12 -LSX and Na 16.7 /Na 12 -LSX, show insulating and metallic states, respectively. The insulating state is changed to the metallic state upon increasing the loading density of Na atoms. The two samples have the space group Fd3̅ attributed to cubic symmetry and lattice constants of a = 2.49646(3) nm for Na 9.4 /Na 12 -LSX and a = 2.495060(11) nm for Na 16.7 /Na 12 -LSX. In both samples, three cation sites at the centers of two types of 6-ring of the sod-cage and the centers of the d6r prism are fully occupied by Na ions. In addition, a large number of Na cations forming Na clusters are distributed in the cavity (supercage), and Na distribution inside the cavity is disorderly, which is represented by several independent sites with low site occupancy. Electron-density distribution analysis clearly reveals the covalent bond of Si(Al)−O and disordered Na distribution in the cavity. In addition, electron densities based on the orbital hybridization between a Na cation and framework oxygen atom are observed around the 12-ring. In Na 16.7 /Na 12 -LSX, the formation of the chain-like Na cation distribution, which connects between the second neighboring cavities, is represented. However, this Na−Na connectivity is not formed in Na 9.4 /Na 12 -LSX. It was identified that the total number of Na cations in the cavity in Na 16.7 /Na 12 -LSX is much larger than that in Na 9.4 /Na 12 -LSX. The cation sites can be classified into two types of character: (a) close to the inner wall of cavity and (b) around the center of cavity and/or at the center of 12-ring pore window. In the domain (b), the number of cations remarkably increases with the increase in n. This change must be strongly related to the insulator-to-metal transition.

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Metal-to-insulator crossover in alkali doped zeolite

Igarashi

Jeglič

Krajnc

et al. 2016

Sci Rep

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We report a systematic nuclear magnetic resonance investigation of the 23Na spin-lattice relaxation rate, 1/T1, in sodium loaded low-silica X (LSX) zeolite, Nan/Na12-LSX, for various loading levels of sodium atoms n across the metal-to-insulator crossover. For high loading levels of n ≥ 14.2, 1/T1T shows nearly temperature-independent behaviour between 10 K and 25 K consistent with the Korringa relaxation mechanism and the metallic ground state. As the loading levels decrease below n ≤ 11.6, the extracted density of states (DOS) at the Fermi level sharply decreases, although a residual DOS at Fermi level is still observed even in the samples that lack the metallic Drude-peak in the optical reflectance. The observed crossover is a result of a complex loading-level dependence of electric potential felt by the electrons confined to zeolite cages, where the electronic correlations and disorder both play an important role.

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Exotic magnetism of s-electron cluster arrays: Ferromagnetism, ferrimagnetism and antiferromagnetism

Cited by 12 publications

References 34 publications

Electrons of alkali metals in regular nanospaces of zeolites

Electrons of alkali metals in regular nanospaces of zeolites

Crystal Structures of Heavily Na-Loaded Low-Silica X (LSX) Zeolites in Insulating and Metallic States

Metal-to-insulator crossover in alkali doped zeolite

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