Continuous melting and thermal-history-dependent freezing in the confined Na-K eutectic alloy

Charnaya, E. V.; Lee, M. K.; Tien, Cheng; Chang, Lo-Yueh; Wu, Zhimin; Kumzerov, Yu. A.; Бугаев, А. С.

doi:10.1103/physrevb.87.155401

Cited by 6 publications

(4 citation statements)

References 29 publications

(45 reference statements)

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“…A thermal hysteresis in NMR has been observed in Na 2 K eutectic alloy in confined geometry of porous glass. 28) A similar structural change may be the origin of the kinks and thermal hysteresis in resistivities of present samples. Further investigations are required to clarify this issue in the future.…”

Section: Electrical Resistivitysupporting

confidence: 53%

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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Section: Electrical Resistivitysupporting

confidence: 53%

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

et al. 2015

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“…For metallic substances NMR acts as another experimental technique which gives valuable information about the internal structure of liquids and solids through measurements of the shift in the resonance frequency, the Knight shift, caused by coupling with conduction elec trons [11]. Studies of the Knight shift were already applied to reveal some striking phenomena in lowdimensional metals such as enhanced polymorphism in sodium nanopar ticles [12], continuous melting in the sodiumpotassium alloy nanoparticles [13], and reduction of electron susceptibility in metals embedded into mesoporous matrices ( [14] and refer ences therein). The Knight shift measurements also showed the transformations in the nanostructured liquid gallium [15].…”

Section: Introductionmentioning

confidence: 99%

Liquid–liquid transition in supercooled gallium alloys under nanoconfinement

Nefedov

Podorozhkin

Charnaya

et al. 2019

J. Phys.: Condens. Matter

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NMR studies of the thermal evolution of the Ga-In-Sn and Ga-In liquid alloys embedded into opal matrices were carried out. Temperature dependences of the gallium lineshape, shift of the resonance frequency (Knight shift), and intensity were obtained upon cooling down to the alloy freezing and subsequent warming. A second highfrequency 71 Ga NMR signal emerged for both alloys upon cooling, the NMR line intensity transferring gradually into this additional signal. The Knight shifts of the signals differed noticeably. The transformations of the gallium line upon warming were continuous and not affected by changes in the alloy compositions induced by melting. 115 In NMR measurements were conducted to monitor the alloy compositions at freezing and melting. The findings suggest the occurrence of the liquid-liquid phase transition in the strongly supercooled alloys under nanoconfinement.

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“…The detection of NMR signals from confined solid metals mentioned above was not achieved because of strong broadening of lines due to the anisotropy of the Knight shift. The NMR signals for confined solid metallic particles were found for the Na-K eutectic alloy embedded into a porous glass [8] and for sodium within silica gel [19].…”

Section: Discussionmentioning

confidence: 99%

“…Charnaya). and references therein) and for metals embedded into nanoporous matrices [8][9][10][11][12]. Until now NMR experiments on metals in confined geometry were mostly carried out for liquid nanoparticles because of strong broadening of resonance lines upon freezing into low-symmetry crystalline structures.…”

Section: Introductionmentioning

confidence: 99%