Structural and magnetic properties of inverse opal photonic crystals studied by x-ray diffraction, scanning electron microscopy, and small-angle neutron scattering

Abstract

The structural and magnetic properties of nickel inverse opal photonic crystal have been studied by complementary experimental techniques, including scanning electron microscopy, wide-angle and small-angle diffraction of synchrotron radiation, and polarized neutrons. The sample was fabricated by electrochemical deposition of nickel in voids in a colloidal crystal film made of 450 nm polystyrene microspheres followed by their dissolving in toluene. The microradian small-angle diffraction of synchrotron radiation was used to reveal the opal-like large-scale ordering proving its tendency to the face-centered-cubic ͑fcc͒ structure with the lattice constant of 650Ϯ 10 nm. The wide-angle x-ray powder diffraction has shown that nanosize fcc nickel crystallites, which form an inverse opal framework, have some texture prescribed by principal directions in inverse opal on a macroscale, thus showing that the atomic and macroscopic structures are correlated. The polarized small-angle neutron scattering is used on the extreme limit of its ability to detect the transformation of the magnetic structure under applied field. Different contributions to the neutron scattering have been analyzed: the nonmagnetic ͑nuclear͒ one, the pure magnetic one, and the nuclear-magnetic interference. The latter in the diffraction pattern shows the degree of the spatial correlation between the magnetic and nuclear reflecting planes and gives the pattern behavior of the reversal magnetization process for these planes. The field dependence of pure magnetic contribution shows that the three-dimensional geometrical shape of the structure presumably leads to a complex distribution of the magnetization in the sample.

Large-scale ZnO inverse opal films fabricated by a sol–gel technique

“…Thus, sol-gel synthesized ZnO inverse opals do not undergo a severe structural degradation and have structural quality comparable to that of colloidal crystal templates. In order to further investigate the crystalline quality of ZnO inverse opals on a macroscale, the samples were studied by microradian X-ray diffraction [23,24]. Fig.…”

Исследование Квазидвумерных И Квазитрехмерных Упорядоченных Пористых Структур Методами Малоугловой Дифракции В Скользящей Геометрии

“…5 соответственно. При осаждении никеля и кобальта в поры кристалла-темплата первый кристаллизуется в ГЦК-структуру [32], второй -в ГПУ [33]. Наличие выделенного направления роста для ГПУ-структуры при кристаллизации в порах оставляет меньше степеней свободы для поверхностной диффузии по сравнению с изотропным случаем.…”

“…В свою очередь, локализованные плазмонные резонансы наблюдаются в ИОПС на основе металлов [30,31], а заполнение опаловых пустот никелем или кобальтом приводит к созданию ферромагнитных ИОПС с распре-делением векторов локальной намагниченности, подчи-няющемуся " правилу льда" [26,27,[32][33][34]. Наиболее совершенные ГЦК-структуры искусствен-ных опалов получают при осаждении сферических ча-стиц из водной суспензии на вертикальную подложку методом формирования регулярной структуры в области мениска при испарении дисперсной среды.…”

Magnetic topology of Co-based inverse opal-like structures

“…In our previous work 35 polarized small-angle neutron scattering (SANS) was used to detect the transformation of the magnetic structure of three-dimensional Ni inverse OLSs under the applied field. Different contributions to the neutron scattering have been analyzed: the nonmagnetic one, the pure magnetic one, and the nuclear-magnetic interference.…”

“…This means that the magnetic scattering is hardly distinguishable because it is superimposed on the highly intensive reflections from the nuclear structure. 35 Luckily, for Co the nuclear scattering amplitude A n is twice as small as the magnetic scattering amplitude A m . In this case the magnetic contribution is much more intense while the nuclear contribution is very weak.…”