Naito T, Fukuda Y. The universal relationship between sample dimensions and cooperative phenomena: effects of fractal dimension on the electronic properties of high-
TC cuprate observed using electron spin resonance.
Phys Chem Chem Phys 2022;
24:4147-4156. [PMID:
35014662 DOI:
10.1039/d1cp04709d]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
As demonstrated by the unique electronic properties of nanostructured materials, which are qualitatively different from the bulk properties of the same materials, there should be a general relationship between the dimensions of the sample structures and the physical/chemical properties. However, it is demanding to examine this intriguing problem experimentally, because one cannot prepare a series of samples based on the same material with systematically varying and noninteger dimensions. This problem is solved by considering the fractal dimensions of samples. The electronic structures of a series of powder samples of the high-TC superconductor YBa2Cu3O7-δ with the fractal dimensions (Df) of 2.5-3.0 were investigated using the electron spin resonance (ESR) spectra at 293 K, to determine a general and quantitative relationship between the electronic properties and fractal dimensions of the samples. The observed Df-dependences of ESR parameters, such as g-values and linewidths, were quantitatively consistent with those of the critical temperatures, critical current densities, and lower critical magnetic fields, all of which exhibited anomalies at Df ∼ 2.9. Considering the geometrical features of the fractal models, a hypothesis for explaining the observed Df-dependences of the cooperative phenomena has been proposed, suggesting a universal structural instability at particular fractal dimensions, which affects all the physical and chemical properties of the samples.
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