Insulator-to-metal transition and magnetism of potassium metals loaded into regular cages of zeolite LSX

Nakano, T.; Hanh, Duong Thi; Owaki, Akihiro; Nozue, Yasuo; Nam, Nguyễn Hoàng; Araki, Shingo

doi:10.3938/jkps.63.512

Cited by 14 publications

(28 citation statements)

References 12 publications

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“…The increase in the resistivity at low temperatures is assigned to the decrease in the DOS at the Fermi energy based on the model shown in Figure 6(a). This increase is likely as a Kondo insulator, because of the correlation interaction between itinerant electrons in supercage network and localized electrons at β-cages [43]. The metallic band of supercage network, however, is narrow and ferromagnetic, and this situation is different from the ordinary Kondo insulator [103].…”

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

confidence: 77%

“…A negative Weiss temperature indicates an existence of the AF interaction between two magnetic sub-lattices of supercages and β-cages. The IMT has been observed at n ≈ 6, and metallic low resistivities have been observed at n 6 at higher temperatures, as shown in Figure 6(b) [43]. Resistivities at higher temperatures ( 50 K) decrease remarkably with n. A remarkable increase in the resistivity, however, is seen with the decrease in temperature for ferrimagnetic samples at n = 8.4 and 9.0.…”

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

confidence: 79%

“…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: Ferrimagnetism and Ferromagnetism In Na-k Alloy System In Zementioning

confidence: 77%

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

confidence: 79%

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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“…[1][2][3][4][5][6][7][8][9][10] These s-electron systems without any magnetic elements are fascinating magnetic materials, where magnetic orderings are realized by the mutual interaction between s-electrons of nanoclusters through windows of zeolite cages. The quantum electronic states of nanoclusters play an important role in the magnetic properties.…”

Section: Introductionmentioning

confidence: 99%

“…In the present paper, we used Na-K-form zeolite low-silica X (LSX) which has a chemical formula of Na x K 12Àx Al 12 Si 12 O 48 per β-cage (or supercage). In previous studies, [7][8][9] a guest K metal was loaded into K-and Na-K-form zeolite LSXs at the K-rich region (0 x 4), and K-and Na-K alloy clusters were generated, respectively. A ferrimagnetism has been observed at higher K-loading densities.…”

Section: Introductionmentioning

confidence: 99%

Ferromagnetism of Na–K Alloy Clusters Incorporated in Zeolite Low-Silica X

et al. 2015

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In a porous crystal of zeolite low-silica X (LSX), β-cages and supercages (cavities) are arrayed in a diamond structure, respectively. We loaded potassium metal into zeolite LSX which has a chemical formula of Na 7.3 K 4.7 Al 12 Si 12 O 48 per β-cage (or supercage), and generated Na-K alloy clusters in β-cages and=or supercages. We have investigated the magnetic properties, the optical ones and the electrical resistivity at various values of K-loading density n per β-cage (or supercage) up to n = 9.7. Localized magnetic moments are observed at 8.2 < n < 9.7. Almost simultaneously, nearly pure ferromagnetism is observed at 8.4 < n < 9.7. The highest Curie temperature is ≈12 K at n ≈ 9. Optical reflection spectra for 8 < n have a new band at 2.8 eV which is assigned to the optical excitation of s-electrons of clusters generated at β-cages. The origin of the magnetic moments is assigned to these β-cage clusters because of the coincidence between the growths of the 2.8 eV band and localized magnetic moments. The origin of magnetic ordering is explained by a ferromagnetic interaction between β-cage clusters. All samples are found to be insulating from the temperature dependence of electrical resistivity. A direct magnetic interaction between β-cage clusters is not expected because of the high electronic barrier between them. A ferromagnetic superexchange coupling between β-cage clusters is newly proposed via the sp 3 -like closed-shell clusters at supercages. A thermal hysteresis is observed in the electrical resistivity at intermediate temperatures, and the origin is assigned to low-density carriers generated in the Na-K eutectic alloy structures in nanospace.

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Decomposition of the potassic rocks by sub‐molten salt method and synthesis of low silica X zeolite

Qingyu

Zhao

Liu

et al. 2016

Asia-Pacific J Chem Eng

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In this work, the potassic rock (PR), an ore rich in aluminosilicate and alkali metal sources, was decomposed to active amorphous material in mild condition for the first time via sub-molten salt method. Low silica X (LSX) zeolite was successfully synthesized using the amorphous precursor from PRs as starting material. The effects of temperature, time, and mass concentration of alkali on the decomposition of PRs powder, and the effects of molar ratios of SiO 2 /Al 2 O 3 and H 2 O/(Na 2 O + K 2 O) on the synthesis of LSX zeolite, were investigated. X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, and Fourier transform infrared spectroscopy were employed to characterize the precursors and as-prepared zeolites. The results indicated that the highly active amorphous precursor can be obtained in (Na, K)OH sub-molten salt medium with 80% of mass concentration of alkali at 190°C for 3.0 h. The LSX zeolite can be synthesized in 5.85Na 2 O:1.65K 2 O:Al 2 O 3 :(2.1-2.3)SiO 2 :(113-125)H 2 O system using the slurry obtained from the decomposition of PRs.

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Insulator-to-metal transition and magnetism of potassium metals loaded into regular cages of zeolite LSX

Cited by 14 publications

References 12 publications

Electrons of alkali metals in regular nanospaces of zeolites

Electrons of alkali metals in regular nanospaces of zeolites

Ferromagnetism of Na–K Alloy Clusters Incorporated in Zeolite Low-Silica X

Decomposition of the potassic rocks by sub‐molten salt method and synthesis of low silica X zeolite

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