Atomistic insights into the morphological dynamics of gold and platinum nanoparticles: MD simulations in vacuum and aqueous media

• Evangelos Voyiatzis,
• Eugenia Valsami-Jones and
• Antreas Afantitis

Beilstein J. Nanotechnol. 2024, 15, 995–1009, doi:10.3762/bjnano.15.81

• . The tessellation is carried out using the Qhull library [78]. The shape of a NP is quantified by the asphericity, b, the acylindricity, c, and the relative shape anisotropy, κ2, parameters [79]. Let denote the eigenvalues of the gyration tensor. The shape parameters are given by: Complementary

• is considerably stronger than on the temperature of the NP. The modifications in the shape of the NPs are tracked by the asphericity, acylindricity, and shape anisotropy parameters. The temperature dependence of these three parameters for the Au and Pt NPs with diameters of 1 nm (i.e., the smallest

• possesses, the acylindricity is zero, while the relative shape anisotropy is one. We observe a distinct behaviour of the small NPs compared to the large ones. In the latter case, the variation in the shape is weak, and minor changes occur only near the transition temperature identified by the Berry

ZnO-decorated SiC@C hybrids with strong electromagnetic absorption

• Liqun Duan,
• Zhiqian Yang,
• Yilu Xia,
• Xiaoqing Dai,
• Jian’an Wu and
• Minqian Sun

Beilstein J. Nanotechnol. 2023, 14, 565–573, doi:10.3762/bjnano.14.47

• that there are some fluctuations in the high-frequency range (10–16 GHz), which are called Debye relaxation peaks. These peaks are caused by shape anisotropy or surface polarization. For the SCZ samples, the unique core–shell structure and the interface polarization effect between different phases may

A new method for obtaining the magnetic shape anisotropy directly from electron tomography images

• Cristian Radu,
• Ioana D. Vlaicu and
• Andrei C. Kuncser

Beilstein J. Nanotechnol. 2022, 13, 590–598, doi:10.3762/bjnano.13.51

• developed in order to increase the reliability of the correlations between morphology and magnetism. Using the Magn3t software, the magnetic shape anisotropy magnitude and direction of magnetite nanoparticles has been extracted for the first time directly from transmission electron tomography. Keywords

• : electron tomography; magnetite; Python; shape anisotropy; Introduction For any nanoparticle (NP) system, among the most important pieces of physical information for scientists is information related to the morphology (size, shape, and organization) of its constituents. In nanoscale systems, this

• addressing strongly desired morphology–magnetism correlations analyzing the shape anisotropy with respect to its magnitude, direction, and statistical distribution of MNPs within the system, starting from tomograms experimentally obtained on real MNP systems. The aspects addressed by the proposed software

Heating ability of elongated magnetic nanoparticles

• Elizaveta M. Gubanova,
• Nikolai A. Usov and
• Vladimir A. Oleinikov

Beilstein J. Nanotechnol. 2021, 12, 1404–1412, doi:10.3762/bjnano.12.104

• nanoparticles are arbitrarily directed with respect to the particle easy anisotropy axes (see below the inset in Figure 1a). Then, the shape anisotropy energy of the assembly of spheroidal nanoparticles can be written as follows: where KSh is the shape anisotropy constant and is the unit vector along the

• direction of elongation of the i-th nanoparticle. The shape anisotropy constant is given by [48]: Here Ms = 450 emu/cm3 is the saturation magnetization of a magnetite nanoparticle [47] and Na is the demagnetizing factor along the long nanoparticle axis. In this work, we also consider the effect of MD

• nanoparticles is straightforward. For magnetite nanoparticles with a high saturation magnetization, the shape anisotropy energy of the particle rapidly increases with increasing aspect ratio. For example, for magnetite a nanoparticle with aspect ratio a/b = 1.25 the shape anisotropy constant is KSh = 1.09 × 105

Free and partially encapsulated manganese ferrite nanoparticles in multiwall carbon nanotubes

• Saja Al-Khabouri,
• Salim Al-Harthi,
• Toru Maekawa,
• Mohamed E. Elzain,
• Ashraf Al-Hinai,
• Ahmed D. Al-Rawas,
• Abbsher M. Gismelseed,
• Ali A. Yousif and
• Myo Tay Zar Myint

Beilstein J. Nanotechnol. 2020, 11, 1891–1904, doi:10.3762/bjnano.11.170

• contributes to a large coercivity. The second factor is the large aspect ratio of the Fe-filled arrays characterized by a large shape anisotropy, which may lead to high coercivity. The saturation magnetization of MnFe2O4/MWCNTs at room temperature is 7.6 emu/g, six times lower than the expected saturation

• due to the existence of a diamagnetic component in CNTs. In the literature, the reported value for MnFe2O4 nanoparticles of 12.5 nm in size is 55 emu/g [27]. From the above analysis it can be concluded that particle size has a major effect on the blocking temperature value. Shape, anisotropy, and

Controlling the proximity effect in a Co/Nb multilayer: the properties of electronic transport

• Sergey Bakurskiy,
• Mikhail Kupriyanov,
• Nikolay V. Klenov,
• Igor Soloviev,
• Andrey Schegolev,
• Roman Morari,
• Yury Khaydukov and
• Anatoli S. Sidorenko

Beilstein J. Nanotechnol. 2020, 11, 1336–1345, doi:10.3762/bjnano.11.118

• electrodes (Figure 5b). The observed variation in the R(T) step-like behavior may also be due to the specific sample geometry (i.e., electrodes with horizontal and vertical orientations, Figure 4a). Due to the shape anisotropy, the “body” of the “centipede” is magnetized along the longitudinal direction

Using gold nanoparticles to detect single-nucleotide polymorphisms: toward liquid biopsy

• María Sanromán Iglesias and
• Marek Grzelczak

Beilstein J. Nanotechnol. 2020, 11, 263–284, doi:10.3762/bjnano.11.20

• optical properties not only in the visible but also in the near-infrared spectral range. Shape anisotropy (rods) and regiospecific surface functionalization (tip versus lateral parts) enable the fabrication of colloidal systems with limited degrees of freedom. In such systems, the possible orientations of

Oblique angle deposition of nickel thin films by high-power impulse magnetron sputtering

• Hamidreza Hajihoseini,
• Movaffaq Kateb,
• Snorri Þorgeir Ingvarsson and
• Jon Tomas Gudmundsson

Beilstein J. Nanotechnol. 2019, 10, 1914–1921, doi:10.3762/bjnano.10.186

• incidence on the structural and magnetic properties of Ni thin films deposited using dcMS and HiPIMS. We chose to work with pure Ni rather than NiFe alloys because it rejects many proposed explanations for uniaxial anisotropy based on alloying, i.e., directional ordering of Fe/Ni atom pairs [46], shape

• anisotropy of an elongated ordered phase [47], composition variation between grains [48] and, more recently suggested, localized composition non-uniformity [49]. Besides, we do not rotate the substrate during the deposition to simplify the conditions at the cost of losing film thickness uniformity

On the relaxation time of interacting superparamagnetic nanoparticles and implications for magnetic fluid hyperthermia

• Andrei Kuncser,
• Nicusor Iacob and
• Victor E. Kuncser

Beilstein J. Nanotechnol. 2019, 10, 1280–1289, doi:10.3762/bjnano.10.127

• anisotropy (as due to only the shape anisotropy), defined along Ox axis (along the MNP length), it is possible to calculate both the magnitude of the anisotropy energy barrier of each particle (e.g., as in Figure 3a,b) or the anisotropy energy of the whole system (e.g., as in Figure 3c) for all the assumed

Magnetic field-assisted assembly of iron oxide mesocrystals: a matter of nanoparticle shape and magnetic anisotropy

• Julian J. Brunner,
• Marina Krumova,
• Helmut Cölfen and
• Elena V. Sturm (née Rosseeva)

Beilstein J. Nanotechnol. 2019, 10, 894–900, doi:10.3762/bjnano.10.90

• orientation of some nanoparticles within the superlattice with <112>magnetite perpendicular to the substrate might be caused by the simultaneous competition of two types of anisotropic interactions between nanoparticles during the assembly process [24]. On one side the particle shape anisotropy promotes face

Heating ability of magnetic nanoparticles with cubic and combined anisotropy

• Nikolai A. Usov,
• Mikhail S. Nesmeyanov,
• Elizaveta M. Gubanova and
• Natalia B. Epshtein

Beilstein J. Nanotechnol. 2019, 10, 305–314, doi:10.3762/bjnano.10.29

• deviation from the nanoparticle shape in a first approximation can be described as small particle elongation in a direction random with respect to the direction of the cubic easy anisotropy axes. For a slightly elongated nanoparticle of a soft magnetic type, the shape anisotropy energy may have an

• small interval 1 < a/b < ξmax. For elongated nanoparticles, in addition to the magneto-crystalline anisotropy energy, Equation 3, there is also a shape anisotropy energy contribution where Ki is the shape anisotropy constant and ni is the unit vector along the direction of elongation of the ith

• nanoparticle. For the shape anisotropy constant one obtains [32] Here Na is the demagnetizing factor along the long nanoparticle axis. Next, the Zeeman energy of the cluster in an applied alternating magnetic field is given by For nearly spherical, uniformly magnetized nanoparticles the magnetostatic energy

Size-selected Fe₃O₄–Au hybrid nanoparticles for improved magnetism-based theranostics

• Maria V. Efremova,
• Yulia A. Nalench,
• Eirini Myrovali,
• Anastasiia S. Garanina,
• Ivan S. Grebennikov,
• Polina K. Gifer,
• Maxim A. Abakumov,
• Marina Spasova,
• Makis Angelakeris,
• Alexander G. Savchenko,
• Michael Farle,
• Natalia L. Klyachko,
• Alexander G. Majouga and
• Ulf Wiedwald

Beilstein J. Nanotechnol. 2018, 9, 2684–2699, doi:10.3762/bjnano.9.251

• the NPs, especially significant for the present octahedra, increase the effective magnetic anisotropy by shape anisotropy which increases quadratically with MS [59]. Experimentally, this was observed by Joshi et al. [74] and Smolensky et al. [75] when they compared spherical and faceted NPs. In both

Magnetism and magnetoresistance of single Ni–Cu alloy nanowires

• Andreea Costas,
• Camelia Florica,
• Elena Matei,
• Maria Eugenia Toimil-Molares,
• Ionel Stavarache,
• Andrei Kuncser,
• Victor Kuncser and
• Ionut Enculescu

Beilstein J. Nanotechnol. 2018, 9, 2345–2355, doi:10.3762/bjnano.9.219

• systems, the nanowires exhibit an additional degree of freedom associated to their inherent shape anisotropy, depending on the aspect ratio (the ratio between the length of the wire and its diameter). Both the aspect ratio and the wire diameter influence the magnetic domain structure of the wire, which is

• the shape anisotropy). It is worth mentioning that Δρ might be positive or negative depending on whether the electron conduction is dominant by spin-up or spin-down electron scattering as well as by the ratio between the spin–orbit coupling parameter and the splitting of the uppermost bands of the

• the wire axis (EA) at zero field (after saturation) due to the shape anisotropy, MRmax in parallel geometry has to be 0 (as experimentally confirmed) whereas in perpendicular geometry . The dependence of the perpendicular magnetoresistance on the applied field in three nanowires SNW1, SNW2 and SNW3 is

Magnetic characterization of cobalt nanowires and square nanorings fabricated by focused electron beam induced deposition

• Federico Venturi,
• Gian Carlo Gazzadi,
• Amir H. Tavabi,
• Alberto Rota,
• Rafal E. Dunin-Borkowski and
• Stefano Frabboni

Beilstein J. Nanotechnol. 2018, 9, 1040–1049, doi:10.3762/bjnano.9.97

• noted that Co carbonyl precursor was chosen here because it has been shown to provide high purity deposits with magnetic properties that are close to those of pure Co [13]. It is well known that shape anisotropy has a profound influence on the magnetic properties of nanostructured materials. The NW is a

• basic building block of magnetic nanodevices, as its high aspect ratio (length/width) often results in a single magnetic domain state due to shape anisotropy [14]. In detail, a NW has a stable magnetic state if its width is smaller than 7·Δd, where Δd is the dipolar exchange length [15], which is ca

• monodomain states, with their magnetization aligned along their long axes due to shape anisotropy [13]. Impurities are present on some samples (especially for the 20 s and 40 s depositions at 5 keV), resulting in flux-closure domain states, which deform the dipole-like phase structure locally. These

Formation and shape-control of hierarchical cobalt nanostructures using quaternary ammonium salts in aqueous media

• Ruchi Deshmukh,
• Anurag Mehra and
• Rochish Thaokar

Beilstein J. Nanotechnol. 2017, 8, 494–505, doi:10.3762/bjnano.8.53

• (monomers) in presence of quaternary ammonium salts. Hydroxide ions and a magnetic moment of the monomers are essential to induce shape anisotropy in the nanostructures. The cobalt nanoplates are studied in detail, and a growth mechanism based on collision, aggregation, and crystal consolidation is proposed

• of a nanoplate. The study explains, hereto unaddressed, the temporal evolution of complex magnetic nanostructures. These ferromagnetic nanostructures represent an interesting combination of shape anisotropy and magnetic characteristics. Keywords: Brownian motion; cobalt nanoplates; electron

• examined in detail. This observation is in agreement with previous studies that suggest that shape anisotropy is observed only above a certain concentration of hydroxide ions [23][24][29]. EDS measurements of well-formed nanoplates showing the presence of cobalt is are given in Figure S4 (Supporting

Properties of Ni and Ni–Fe nanowires electrochemically deposited into a porous alumina template

• Alla I. Vorobjova,
• Dmitry L. Shimanovich,
• Kazimir I. Yanushkevich,
• Sergej L. Prischepa and
• Elena A. Outkina

Beilstein J. Nanotechnol. 2016, 7, 1709–1717, doi:10.3762/bjnano.7.163

• ; Introduction Arrays of vertically arranged metallic NWs have attracted a lot of attention due to their shape anisotropy and extremely large surface area. The combination of this unique structure with uncommon magnetic, optical and transport properties can be used to develop novel functional nanomaterials for

Customized MFM probes with high lateral resolution

• Óscar Iglesias-Freire,
• Miriam Jaafar,
• Eider Berganza and
• Agustina Asenjo

Beilstein J. Nanotechnol. 2016, 7, 1068–1074, doi:10.3762/bjnano.7.100

• influence of the dominating shape anisotropy (as deduced from the cross-tie domain walls [22] seen in Figure 1c), in agreement with the macroscopic hysteresis loops measured at room temperature by VSM (Figure 1d). A high remanent magnetization of 82% of the saturation value is found when an IP field is

• applied. This, together with the shape anisotropy induced by the pyramidal tip, forces the magnetic moments to remain mainly oriented along the pyramid surface. Nevertheless, the orientation of the spins at the apex will depend on the apex shape and on the way the cobalt layer covers it. Results and

Magnetic switching of nanoscale antidot lattices

• Ulf Wiedwald,
• Joachim Gräfe,
• Kristof M. Lebecki,
• Maxim Skripnik,
• Felix Haering,
• Gisela Schütz,
• Paul Ziemann,
• Eberhard Goering and
• Ulrich Nowak

Beilstein J. Nanotechnol. 2016, 7, 733–750, doi:10.3762/bjnano.7.65

• spherical masks for the production of magnetic antidot lattices. In magnetic antidot films, the nanoscale periodic structure of holes introduces an in-plane shape anisotropy to the otherwise isotropic in-plane properties of polycrystalline or amorphous thin films. Additionally, the holes may act as

• magnetic properties of in-plane magnetized antidot films. Integral magnetometry averaging over all in-plane angles of the antidots with respect to the external field proves that the system is highly dominated by the local shape anisotropy introduced by the hole sites. We identify two distinct switching

• interactions. In our simulations, the elongated sample size (2 × 8 µm2) results in anisotropy along the long axis while we do not observe any shape anisotropy of the channel at an aspect ratio of 8 in our experiment. To account for this discrepancy we have modified our simulations by applying an additional

Focused particle beam-induced processing

• Michael Huth and
• Armin Gölzhäuser

Beilstein J. Nanotechnol. 2015, 6, 1883–1885, doi:10.3762/bjnano.6.191

• article by Gian Carlo Gazzadi and Stefano Frabboni [6]. This leads into the important application field of magnetic nanostructures obtained by FEBID. Luis Rodríguez and coworkers present a detailed study on the influence of shape anisotropy and surface oxidation on the magnetization reversal of thin, iron

Structural and magnetic properties of iron nanowires and iron nanoparticles fabricated through a reduction reaction

• Marcin Krajewski,
• Wei Syuan Lin,
• Hong Ming Lin,
• Katarzyna Brzozka,
• Sabina Lewinska,
• Natalia Nedelko,
• Anna Slawska-Waniewska,
• Jolanta Borysiuk and
• Dariusz Wasik

Beilstein J. Nanotechnol. 2015, 6, 1652–1660, doi:10.3762/bjnano.6.167

• identical, this observation is surprising at the first moment. In general, the effective anisotropy of the nanowires should be much higher due to the high uniaxial shape anisotropy, which is increased by the magnetocrystalline anisotropy with the easy axis oriented along the wire length caused by the

• between them. These interactions result in the strong uniaxial shape anisotropy with the easy axis of magnetization parallel to the length of the wires. This stabilizes the magnetization distributions and causes that the squareness ratio (MR/Ms) is higher in the studied nanowires. Besides that, the

Influence of the shape and surface oxidation in the magnetization reversal of thin iron nanowires grown by focused electron beam induced deposition

• Luis A. Rodríguez,
• Lorenz Deen,
• Rosa Córdoba,
• César Magén,
• Etienne Snoeck,
• Bert Koopmans and
• José M. De Teresa

Beilstein J. Nanotechnol. 2015, 6, 1319–1331, doi:10.3762/bjnano.6.136

• producing the magnetization reversal. Most of magnetic devices work by producing a voltage output when the magnetization reversal occurs. In the case of cobalt deposits, it was previously found that the coercive field is governed by shape anisotropy [24] due to the polycrystalline microstructure [25], and

• valve in the GIS and had to be optimized in order to obtain deposits exhibiting ferromagnetic properties with suitable shape anisotropy. In these experiments, the nominal turbopump speed is 260 L/s for nitrogen gas. When the leak valve is opened, the chamber pressure increases. The chamber pressure is

• decreased to the range from 3 × 10−6 to 4 × 10−6 mbar, the deposits did not show the granular structure and the magnetization reversal was found to be dominated by shape anisotropy (see next section). In situ compositional analysis by energy dispersive X-ray spectroscopy (EDS) indicated that the Fe content

Tunable magnetism on the lateral mesoscale by post-processing of Co/Pt heterostructures

• Oleksandr V. Dobrovolskiy,
• Maksym Kompaniiets,
• Roland Sachser,
• Fabrizio Porrati,
• Christian Gspan,
• Harald Plank and
• Michael Huth

Beilstein J. Nanotechnol. 2015, 6, 1082–1090, doi:10.3762/bjnano.6.109

• the sample plane and, hence, the out-of-plane magnetization was probed by the measurements. This means that first the shape anisotropy of the stripe had to be overcome and all recorded loops relate to the hard-axis magnetization behavior. The reference Co-based sample A shows no hysteresis, whereby U

• carbon. Thus, in the course of the reaction, carbon is partially removed from the deposit causing a reduction of the deposit thickness. The magnetic behavior of the thin polycrystalline Co stripe A is dominated not by the magnetocrystalline anisotropy, but rather by the shape anisotropy causing the

Cathode lens spectromicroscopy: methodology and applications

• T. O. Menteş,
• G. Zamborlini,
• A. Sala and
• A. Locatelli

Beilstein J. Nanotechnol. 2014, 5, 1873–1886, doi:10.3762/bjnano.5.198

• map in Figure 10b (right panel). This is a surprising confirmation of the magnetocrystalline anisotropy strength dominating the shape anisotropy. Iron oxides find wide application in several fields of research, among others magnetism and heterogeneous catalysis. In both cases, the heteroepitaxial

Designing magnetic superlattices that are composed of single domain nanomagnets

• Derek M. Forrester,
• Feodor V. Kusmartsev and
• Endre Kovács

Beilstein J. Nanotechnol. 2014, 5, 956–963, doi:10.3762/bjnano.5.109

• anisotropies [1]. A nanomagnet with high shape anisotropy must have some kind of modulation in order to reduce the height of the anisotropy energy barrier. This is typically done through doping in order to reduce the saturation magnetization of the nanomagnet. In recent years amorphous ferromagnetic materials

• system to locate the metastable states that exist in the energy landscape. The size of the shape anisotropy energy barrier is a function of the saturation magnetization, the geometry of the nanomagnet and its demagnetization factors. These demagnetization factors, Nx,y,z, are defined by length scales

• particle there may be induced higher multipoles which add additional contributions into the overall interaction. Thus, the resulting interaction between the particles depends on the relative interaction between them, so that the shape anisotropy will play a key role. Recently, Serantes et al. [10] produced

Spin relaxation in antiferromagnetic Fe–Fe dimers slowed down by anisotropic Dy^III ions

• Valeriu Mereacre,
• Frederik Klöwer,
• Yanhua Lan,
• Rodolphe Clérac,
• Juliusz A. Wolny,
• Volker Schünemann,
• Christopher E. Anson and
• Annie K. Powell

Beilstein J. Nanotechnol. 2013, 4, 807–814, doi:10.3762/bjnano.4.92

• experimentally. By using Mössbauer spectroscopy we have shown how minor changes in the electronegativity of the atoms in the ligand sphere and in the donor–acceptor nature of the substituents, and their position on the aromatic ring, can control the shape anisotropy of the DyIII ions and, thus, their interaction

• polarization, and thus the shape anisotropy of the DyIII ion and its interaction with the iron centres can be controlled. This means that the Ln anisotropy can be influenced not only by altering crystal field, but also by an external source. But, surprisingly, this is not always the case. It seems that the