Magnetic topology of Co-based inverse opal-like structures

Abstract

The magnetic and structural properties of a cobalt inverse opal-like crystal have been studied by a combination of complementary techniques ranging from polarized neutron scattering and superconducting quantum interference device (SQUID) magnetometry to x-ray diffraction. Microradian small-angle x-ray diffraction shows that the inverse opal-like structure (OLS) synthesized by the electrochemical method fully duplicates the threedimensional net of voids of the template artificial opal. The inverse OLS has a face-centered cubic (fcc) structure with a lattice constant of 640 ± 10 nm and with a clear tendency to a random hexagonal close-packed structure along the [111] axes. Wide-angle x-ray powder diffraction shows that the atomic cobalt structure is described by coexistence of 95% hexagonal close-packed and 5% fcc phases. The SQUID measurements demonstrate that the inverse OLS film possesses easy-plane magnetization geometry with a coercive field of 14.0 ± 0.5 mT at room temperature. The detailed picture of the transformation of the magnetic structure under an in-plane applied field was detected with the help of small-angle diffraction of polarized neutrons. In the demagnetized state the magnetic system consists of randomly oriented magnetic domains. A complex magnetic structure appears upon application of the magnetic field, with nonhomogeneous distribution of magnetization density within the unit element of the OLS. This distribution is determined by the combined effect of the easy-plane geometry of the film and the crystallographic geometry of the opal-like structure with respect to the applied field direction.

Colloidal Crystals of Spheres and Cubes in Real and Reciprocal Space

“…Small angle X-ray scattering (SAXS) provides insight into the characteristics of colloidal suspensions on the spatial correlations and long-range order in crystals but also in terms of averaged particle size and shape [22,42,[118][119][120][121] . The bottom part of Figure 1.7 shows a schematic representation of the SAXS setup.…”

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

“…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.…”

Periodic order and defects in Ni-based inverse opal-like crystals on the mesoscopic and atomic scale

“…4(a) with dark circles. According to our previous papers [5,11,[17][18][19][20], these rods can be related either to the finite thickness of the colloidal crystal or to increased amount of planar defects and mechanical stress in the crystal. Apart from this, the paper [21] demonstrates surface truncation to be a probable reason for the appearance of the rods.…”

“…(8) divided by the lattice parameter at that temperature was averaged over the same temperature range as in Ref. [54], i.e., 173-298 K. In particular, the obtained CT E value for the samples with a large number of layers (Ni 17 and Ni 26 ) is (1.33 ± 0.05) × 10 −5 K −1 , which agrees with the value for Ni thin film presented in Ref. [54] ((1.37 ± 0.04) × 10 −5 K −1 ) and higher than that for bulk Ni (1.24 × 10 −5 K −1 ).…”

“…Another interpretation is still to consider such a structure as fcc, while with a considerable amount of stacking faults [16]. Also, our previous works [5,11,[17][18][19][20] on this issue demonstrated effectiveness of the mesostructure determination using small-angle neutron and synchrotron diffraction.…”