In the present work, the dynamics of the spins and the structural parameters of thermal treated samples of Eu1−xFexCrO3 (x = 0, 0.1 and 0.2) were investigated. The ac-magnetic susceptibility (χac) ...was measured near TN for frequencies (f) in the range 10 - 104 Hz, magnitude of the ac magnetic field of 10 Oe and for 5 ≤ T ≤ 300 K. X-ray diffraction data were used for determining the lattice parameters and the bonding angle θB (Cr– O(2) – Cr) for 100 ≤ T ≤ 300 K. The maximum in χac was found to shift to higher values of T for increasing values of f. The Vogel-Fulcher law was used for analyzing χac yielding values for the characteristic relaxation time τ0, activation energy Ea/kB and glassy temperature TG, respectively, in the ranges 2.10 - 3.96 ps, 46.5 - 47.2 K and 169.9 -176.1 K. The super-exchange parameter J∼cos4180−θB/2/d7, where d is the length of the bound Cr-O(2), was also obtained yielding a good correlation with the corresponding values of TN.
Continuous (NC-1) and composition-modulated (NC-2 and NC-3) nanowires were successfully synthesized through electrodeposition using porous alumina membranes as templates. Scanning electron microscopy ...was employed to estimate the total length of the nanowires, revealing lengths of 7.48 ± 1.03 μm, 5.56 ± 0.77 μm, and 8.23 ± 0.82 μm for NC-1, NC-2, and NC-3, respectively. The composition-modulated samples exhibited distinct light and dark regions along the wires, as revealed by EDS mapping. The light regions (L
Ni
) demonstrated an increased signal for nickel and a reduced signal for copper, while the dark regions (L
Cu
) exhibited the reverse behavior. For NC-2, L
Ni
= 309.94 ± 65 nm and L
Cu
= 64.45 ± 18 nm, whereas for NC-3, it was L
Ni
= 382.25 ± 71 nm and L
Cu
= 139.71 ± 28 nm. X-ray diffraction patterns confirmed the presence of nickel with a face-centered cubic structure in NC-1, while both NC-2 and NC-3 exhibited diffraction peaks corresponding to nickel and metallic copper, both with fcc structures. Utilizing XRD standards and the Williamson-Hall method, the crystallite size and lattice deformation of nickel were estimated, resulting in values of
D
= 69 nm and
ε
= 0.0051% for NC-1,
D
= 18 nm and
ε
= 0.0007% for NC-2, and
D
= 53 nm and
ε
= 0.0041% for NC-3. These structural parameters were observed to vary with the deposition current. Magnetization versus field measurements and ferromagnetic resonance analysis provided insights into how the modulation process influenced the magnetic anisotropy, coercivity, remanence, and resonance field of the nanowires. The findings highlight the capability of the composition modulation process to tune the structural and magnetic properties of nanowires, thereby offering potential for the development of advanced electronic devices.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using the COSINE-100 array of NaI(Tl) crystal detectors at the Yangyang Underground ...Laboratory. The signal would be an excess of events with energies above 4 MeV over the well-understood background. Because no excess of events are observed in a 97.7 kg·yr exposure, we set limits on BDM interactions under a variety of hypotheses. Notably, we explored the dark photon parameter space, leading to competitive limits compared to direct dark photon search experiments, particularly for dark photon masses below 4 MeV and considering the invisible decay mode. Furthermore, by comparing our results with a previous BDM search conducted by the Super-Kamionkande experiment, we found that the COSINE-100 detector has advantages in searching for low-mass dark matter. This analysis demonstrates the potential of the COSINE-100 detector to search for MeV electron recoil signals produced by the dark sector particle interactions.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The magnetic properties of the double perovskites Sm2Mn1+xCo1−xO6 (x = 0, 0.05, 0.12 and 0.26) were investigated. It was found that the Curie temperature, the lattice parameters and the net ...magnetic moments increased for increasing amounts of Co. An irreversible behavior was observed by measuring the magnetization after cooling the sample with and without applied magnetic fields (H). The temperature below which the irreversibility was observed is H dependent and the data were nicely fit to de Almeida-Thouless lines. The ac magnetic susceptibility was measured for frequencies f in the range 0.03-10 kHz yielding for the shifting in the freezing temperature per decade of f . The spin-dynamics were found to follow a power-law with a product of the critical exponents of about 4.99. The overall results are understood within a framework where the variation in the bonding angle associated to the super-exchange interactions are taken into consideration.
•The influence of the type of deposition solution and pH is presented for nickel nanowires.•The influence of pH is evident as it alters the deposition rate if we use pH of 2.5 and 3.5.•The FMR ...resonance field values showed evidence of structural changes within the wires.
This study presents the influence of pH and precursors present in the electrolyte on the microstructure and magnetic properties of nickel nanowires. Polycarbonate membranes were used as a template for electrodeposition of nanowires. The SEM results showed that the wires have lengths ranging from 2.68 ± 0.28 µm to 18.77 ± 1.18 µm. X-ray diffraction confirmed the fcc structure of Ni0 and demonstrated how different solutions can modify the reflection intensity of the peaks. Finally, ferromagnetic resonance spectra demonstrated how pH and precursors present in the electrolyte can modify the ferromagnetic response of NiNWs grown on polycarbonate membranes, emphasizing the influence of both factors on the magnetic behavior of nanowires. This study provides an understanding of the role that solution chemistry plays in the manufacture of magnetic nanomaterials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The synergistic effects of a hybrid nanocomposite (Fe3O4@NrGO) and their influence on electromagnetic pollution shielding (EMI SE) were explored. This is a current concern where the impacts need to ...be fully clarified and assertively addressed. Thus, the main focus of the paper was based on the physical and mechanical properties of porosity, surface area, flexibility and, mainly, electrical conductivity of the graphene aerogels, which do not require the use of a binder and are of great interest for the EMI SE area. The precursors (rGO, NrGO and Fe3O4), as well as the nanocomposite, underwent thorough structural characterisation to understand their nature. Characteristic bands of C-N/C=N bonds and a content of 8.03 at% N were identified, with a high N:O ratio of 1.31, indicating efficient doping of the conductive matrix. The aerogel NrGO phase, with a quality of just 5 layers, and the Fe3O4 phase, with domains around 5 nm, were confirmed, as well as the superposition of the signals in the Fe3O4@NrGO pattern. Electron microscopy images and elemental map also demonstrated the efficient distribution of Fe3O4 in the matrix and its porous appearance. Thus, leveraging the advantages of aerogel, extremely light ultra-thin pellets measuring 0.1 mm and weighing 10 mg were produced. The high nitrogen doping of the graphene network, the presence of magnetic nanoparticles, as well as the high surface area and porosity achieved in the production of the nanocomposite, were responsible for high specific shielding effectiveness of 2730 dB · cm−1 at 10.7 GHz and an average in the X-band of 1590 dB · cm−1. Thus, the improved and synergistic mechanisms highlighted the promising advantages of using these highly porous doped materials, demonstrating that the Fe3O4@NrGO hybrid presents high value for investigations in the application of EMI SE.
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•The Fe3O4@NrGO hybrid nanocomposite presented a synergistic contribution to EMI SE.•The properties of aerogel allowed to obtain light, thin and binder-free pellets.•The specific EMI SE was higher than those reported for graphene-based materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study investigates the influence of sintering temperature on the structural and magnetic properties of Y
3
Fe
4,97
La
0,03
O
12
, elucidating the nucleation and growth mechanisms related to ...temperature. Through meticulous X-ray diffraction analysis, we confirmed the formation of a single YIG phase at 900 °C. Conversely, samples sintered at 1000 °C and 1100 °C reveal the presence of a second phase, attributed to YFeO
3
, highlighting the complex interaction between sintering temperature and material morphology. Moreover, magnetic characterization details how sintering temperatures directly influence the magnetic moment and saturation magnetization of the nanoparticles, presenting significant fluctuations in magnetic properties due to the presence of the secondary phase. This work not only sheds light on the subtle relationship between lanthanum doping, sintering temperature, and the resulting magnetic properties but also paves the way for fine-tuning these properties in advanced materials for specific technological applications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The tuning of magnetic properties in nanostructured systems by chemical substitution provides excellent opportunities to further explore new functionalities together with the involved physics. Here ...we present structural, microstructural and magnetic properties of Eu
1
-
x
Ho
x
CrO
3
(
x
= 0.0, 0.5 and 1.0) nanoparticles prepared by a combustion reaction technique. The substitution of Eu for Ho disturbs the system leading a shrinkage of the unit cell volume from 224.6(8)Å
3
for
x
= 0.0 to 218.3(8)Å
3
for
x
= 1.0, in agreement with previous results and coincident with a contraction of 3.5% of the Cr–O1–Cr bond angle as revealed by X-ray diffraction measurements. From dc magnetic susceptibility measurements, it is also observed a strong reduction of the Néel and Curie–Weiss temperatures (from T
N
Cr
= 178.0(3) K and
Θ
CW
Cr
= − 477(8) K for
x
= 0.0 to T
N
Cr
= 140.0(3) K and
Θ
CW
Cr
= − 22(2) K for
x
= 1.0) associated with the Cr
3
+
–Cr
3
+
interaction. Low temperature magnetization measurements (M vs H) reveal a weak ferromagnetic component as Ho enters the system suggesting alteration of the internal molecular field due to structural modifications. The structure-magnetism correlation can be explained combining Van-Vleck susceptibility, the antisymmetric exchange (Dzyaloshinskii–Moriya interaction) including the Cr–O1–Cr angle modification and the conventional Curie–Weiss analysis at high temperatures.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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