Abstract
We report on experimental evidence of non-conversional pairing in In and Sn nanoparticle assemblies. Spontaneous magnetizations are observed, through extremely weak-field magnetization and neutron-diffraction measurements, to develop when the nanoparticles enter the superconducting state. The superconducting transition temperature TC shifts to a noticeably higher temperature when an external magnetic field or magnetic Ni nanoparticles are introduced into the vicinity of the superconducting In or Sn nanoparticles. There is a critical magnetic field and a critical Ni composition that must be reached before the magnetic environment will suppress the superconductivity. The observations may be understood when assuming development of spin-parallel superconducting pairs on the surfaces and spin-antiparallel superconducting pairs in the core of the nanoparticles.
Highlights
We report on experimental evidence of non-conversional pairing in In and Sn nanoparticle assemblies
A smaller MS was obtained for Ni NPs, showing the core spins dominate over the surface spins in Ni NPs
It is very unlikely that an external magnetic field as weak as 300 Oe can cause a 5% softening in phonon frequencies to account for the 17% increase in TC
Summary
We report on experimental evidence of non-conversional pairing in In and Sn nanoparticle assemblies. Spontaneous magnetizations are observed, through extremely weak-field magnetization and neutron-diffraction measurements, to develop when the nanoparticles enter the superconducting state. The BSC mechanism explains most, if not all, of the physical properties associated with the so-called conventional weak-coupling superconductor In this context, the elements In and Sn, in their bulk form, behave as a standard BCS-type superconductor, where the magnetic environment will destroy the spin-singlet pairings. Cooper-pair moments can develop in the superconducting state that is associated with a spin-triplet pairing, as has been observed in Sr2RuO4 by polarized neutron diffraction studies[10,11]. T C of the superconducting nanoparticles increases noticeably, when magnetic Ni nanoparticles are introduced into the vicinity of the superconducting nanoparticles These effects are reversed when the external magnetic field reaches a critical strength or when the concentration of the Scientific Reports | (2022) 12:775. These results indicate the appearance of non-conventional coupling for the superconductivity of In and Sn nanoparticles
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