Powered by Indico
v3.2.3
Host: Prof. Vadim Grinenko
Venue: TDLI Meeting Room N601
Tencent meeting link: https://meeting.tencent.com/dm/bCxujOuK7OXx
Meeting ID: 259140514, no password
Abstract:
Proximity effects at the interface between two media are currently being actively studied. Of par-ticular interest are two-dimensional low-dimensional structures with superconducting and ferromag-netic properties, in which the interaction of two antagonistic order parameters is realized. One of the most effective methods for studying the magnetism of thin films is polarized neutron reflectometry, which allows obtaining isotopic and magnetic profiles in depth with nanometer resolution. The REMUR polarized neutron reflectometer, located on the 8th channel of the IBR-2 pulsed reactor (Dubna), is one of the most luminous reflectometers in the world, with a neutron flux on the sample of Φ = 3∙105 n∙s-1∙cm-2. This reflectometer is a time-of-flight reflectometer with an operating range of neutron wavelength λ≈1-15 Å. Low-temperature studies of proximity effects in superconducting-ferromagnetic systems and rare-earth films with nontrivial magnetic ordering were carried out on the REMUR reflectometer.
Layered structures of various types are studied in neutron optics: neutron resonators with the pos-sibility of implementing the regime of amplified standing neutron waves [1-3] and periodic superlat-tices [4-5]. It is shown that in periodic layered systems with layer thicknesses of the order of correla-tion lengths, complex coherent phenomena can be realized, for example, the realization of a magnetic superconductor [4], or a multilayer helimagnet [5]. The study of layered systems with a long-range or-der, but without a period, the so-called layered Fibonacci systems, is relevant. Layered photonic Fibo-nacci crystals have long been studied and, in particular, they have shown the possibility of amplifying secondary photoluminescence signals [6]. It is shown that systems with a long-range order, but with-out periodicity, are more stable, in particular, they can realize a longer lifetime of quantum states com-pared to periodic systems [7]. This approach is also known in natural systems, in particular, phyllotax-is [8]. Nontrivial phenomena in layered Fibonacci systems are theoretically predicted. In [9], it was shown that in superconducting systems, the Fibonacci chain implements three superconducting transi-tions in series, and the possibilities of the Josephson effect in such chains are shown [10]. In [11], the effect of anomalous magnetoresistance in layered Fibonacci systems was predicted.
In this paper, neutron-optical calculations of layered Fibonacci systems are performed. Conver-gence of the reflection coefficient is established. Calculations of the neutron reflection coefficient for the quasiperiodic Gd(2 nm)/Nb(25 nm) structure showed that, starting from the Fibonacci order F=10 further increase in the order of the structure practically does not affect the reflection coefficient. This indicates the achievement of a certain limit in the formation of neutron-optical properties of the struc-ture with increasing complexity of the quasi-periodic ordering. Comparison of neutron reflection coef-ficients for quasiperiodic, periodic, and disordered structures has shown the presence of well-defined "quasi-Bragg" peaks in the quasiperiodic structure. This confirms the existence of a long-range order in a quasi-periodic system, despite the absence of strict periodicity. The effect of neutron absorption is investigated. It is shown that, under certain conditions, a quasicrystalline structure can absorb more neutrons than a similar periodic structure. The first artificial layered Fibonacci crystals of the Co/Pt, Co/Pb, and Co/Py types for the Fibonacci order F=10 are synthesized. XRR and TEM data showed high quality of the obtained structures. The first neutron reflection from a quasi-periodic layered sys-tem is obtained.
References：
[1] Guasco L., et al. // Nature Communications, Vol. 13, No. 1, pp. 1-8 (2022).
[2] Khaydukov Yu.N. et al. // Physics of Particles and Nuclei Letters, Vol. 21, No. 5, pp. 1065-1068 (2024)
[3] Khaydukov Yu.N. et al. // Phys. Rev. B, 97, 144511 (2018)
[4] Khaydukov Yu.N. et al. // Phys. Rev. B, 99, 140503 (2019)
[5] Devyaterikov D. I. // Journal of Surface Investigation, Vol. 16, No. 5, pp. 839–842 (2022).
[6] Valy Vardeny Z. et al. // Nature Photonics, Vol. 7, pp. 177-187 (2013)
[7] Philipp T. Dumitrescu, et al. // Nature, Vol 607, 463 (2022).
[8] Левитов Л.С. // Письма в ЖЭТФ, том 54, вып. 9, стр. 542 – 545 (1991).
[9] Quanyong Zhu et al. // Physical Review B 112, 134503 (2025).
[10] Ignacio Sardinero et al. // arXiv:2507.19147 (2025).
[11] Machado L.D. et al. // Physical Review B 85, 224416 (2012).
Biography:
2025 – Present
2023-2024
2021-2023
2014 – 2021