This study explored the microstructural and magnetic features of NiFe
2−
x
Dy
x
O
4
(
x
≤ 0.10) NPs (nanoparticles) that were synthesized by sol–gel auto-combustion method. The single phase of ...spinel ferrite has been verified for all samples without any impurity. The cubic morphology of the products was also showed by SEM. Room temperature (300 K) and 10 K magnetization curves were recorded applying a dc magnetic field up to ±50 kOe and it was observed that magnetic features of NiFe
2
O
4
NPs significantly changed by the substitution of Dy
3+
ion. Magnetization measurements showed low order of 300 and 10 K magnetic parameters (such as
K
eff
, coercivity and anisotropy field values), revealing soft ferrimagnetic behaviors of all pristine and doped NiDy
x
Fe
2−
x
O
4
(0.00 ≤
x
≤ 0.10) NPs at both 300 and 10 K. Pristine NiFe
2
O
4
has maximum magnetic moment and saturation magnetization values among all samples. Dy
3+
substitution showed a slight decrement in magnetization values compared with pristine sample. A slight increase in coercivity was noticed with Dy
3+
substitution. Squareness ratios (SQRs) have a range between 0.144 and 0.324. These values are smaller than the theoretical limit of 0.50, implying the multi-domain nature for NPs. Blocking temperature (
T
B
) was calculated as 28 K for NiFe
2
O
4
NPs.
Pure phase of NiDy
x
Fe
2−
x
O
4
(0.00 ≤
x
≤ 0.10) nanoparticles were prepared via sol–gel auto-combustion process. The structure, morphology, and magnetic properties were investigated.
Highlights
NiFe
2−
x
Dy
x
O
4
(
x
≤ 0.10) NPs were prepared via sol–gel auto-combustion method.
XRD analysis indicates the formation of pure single phase of spinel ferrites.
NiFe
2−
x
Dy
x
O
4
(
x
≤ 0.10
)
NPs exhibit soft ferrimagnetic nature.
All prepared NiFe
2−
x
Dy
x
O
4
(
x
≤ 0.10) NPs displayed a multi-domain nature.
Blocking temperature (
T
B
) was calculated as 28 K for NiFe
2
O
4
NPs.
This paper studied the exchange coupling performance beside structural and microwave properties of SrFe12O19 (SFO) and x(CoTm0.01Tb0.01Fe1.98O4) (CoTmTb) (x ≤ 3.0) hard/soft ferrites nanocomposites ...(NCs). The structure and morphology of NCs were investigated by XRD, SEM, TEM and HR-TEM. Diffuse reflectance spectroscopic (DRS) measurements were applied on hexagonal ferrite, on spinel ferrite nanoparticles and on hard/soft NCs to specify the optical properties. Estimated Eg data are in a range between 1.32 and 1.79 eV. The magnetic properties were also inspected via measurements of magnetization (M) against magnetic field (H) at 300 K (RT) and 10 K (LT). The measurements performed at RT along with the plots of dM/dH versus H indicated that the NCs display good magnetic properties (exchange coupling behavior). The magnetic parameters such as (Ms, Mr, and Hc) show an enhancement in their values with an increasing the soft content at RT. Similarly, the maximum energy product (BH)max rises and reaches its max value for SFO/3(CoTmTb) NCs. Microwave properties of the SFO/x(CoTmTb) NCs were measured in the frequency range 33–50 GHz. From measured S11 and S21 parameters the main electrodynamic characteristics – permittivity and permeability (real and imaginary parts) were computed.
BaBixLaxFe(12−2x)O19 (0.0≤x≤0.5) hexaferrites were synthesized by solid state synthesis route and the effects of Bi, La substitutions on structural, magnetic and optical properties were investigated. ...X-ray powder diffraction, Scanning electron microscopy, Vibrating sample magnetometer, and Percent diffuse reflectance spectroscopy were used to study the physical properties. Room temperature specific magnetization (M–H) curves revealed the ferromagnetic nature of all products. The increasing Bi, La compositions increased the magnetic properties at different magnitudes with respect to undoped BaFe12O19 sample. The maximum values of remnant specific magnetization (Mr=30.3emu/g), extrapolated specific saturation magnetization (Ms=62.12emu/g), and magneton number (nB=16.27) were recorded from BaBi0.2La0.2Fe11.4O19 hexaferrite. The average crystallite size varies in a range of (37.35–51.36)nm. The coercive field (Hc) of undoped hexaferrites is 1180Oe and increased to maximum 2320Oe belonging to BaBi0.4La0.4Fe11.2O19. Magnetic anisotropy was confirmed as uniaxial and calculated effective anisotropy constants (Keff) are between 4.27×105Ergs/g and 5.05×105Ergs/g. The high magnitudes of magnetocrystalline anisotropy (Ha) above than 16,200Oe revealed that all samples are magnetically hard materials. The Tauc plots were drawn to extrapolate the direct optical energy band gap (Eg) of hexaferrites. The Eg values decreased from 1.76eV to 1.47eV with increasing Bi, La compositions.
•BaBixLaxFe(12−2x)O19 (0.0≤x≤0.5) hexaferrites were synthesized by solid state synthesis route.•The Eg values decreased from 1.76eV to 1.47eV with increasing Bi, La compositions.•BaBixxLaxxFe12-2xO19 hexaferrites good candidate for potential applications such as optical sensors, magnetic recording media of high density.
In this study, various Co0.5Ni0.5BixFe2-xO4 (x ≤ 0.10) spinel ferrite nanofibers (CoNiBi SFNFs) have been synthesized by electrospinning technique. The structure, morphological, and magnetic features ...of CoNiBi SFNFs was investigated. XRD analysis demonstrated the formation of single-phase cubic spinel structure for all samples. The cell parameter is increasing with the increase of Bi3+ content. The cubic morphology of all products was also verified by SEM and TEM microscopies. Mössbauer analysis was used to determine the hyperfine parameters by fitting room temperature mosspectra. The Bi3+ ions occupy mainly the B site. Vibrating sample magnetometry (VSM) was applied to get magnetic data for CoNiBi SFNFs at 300 and 10 K. The characteristics of the recorded magnetic hysteresis curves revealed the existence of just ferrimagnetic phases for all fabricated spinel nanofiber samples at both temperatures. The remanent magnetization Mr, saturation magnetization MS, magnetic moment per formula nB, coercivity Hc have been determined. Bi3+ ion substitution commonly diminishes the magnetic data except the content of x = 0.04. The maximum and minimum magnitude of magnetic parameters belong to Co0.5Ni0.5Bi0.04Fe1.96O4 and Co0.5Ni0.5Bi0.10Fe1.90O4SFNFs, respectively. Pristine Co0.5Ni0.5Fe2O4 and Bi3+ ion doped samples exhibit soft magnetic at 300 K and hard magnetic nature at 10K conditions. Squareness ratio (SQR = Mr/Ms) provided extra information about the domain structure of fabricated nanofiber samples. At 10K conditions, SQR of the sample Co0.5Ni0.5Bi0.04Fe1.96O4 is almost equal to 0.5 and this critical value is assigned to the formation of single domains with uniaxial symmetry for this nanofiber. This one only and all others have SQRs that are much lower (0.073–0.366) at 300K or higher (0.620–0.781) at 10K. Those ranges specify the multi-domain wall structure for samples.
•Spinel ferrite nanofibers (CoNiBi SFNFs) have been synthesized by electrospinning technique.•Mössbauer spectra revealed the Bi3+ ions occupy mainly the B site.•The magnetization measurements at variable magnetic field (M − H) disclosed ferrimagnetic phases at 300 and 10 K.
In the current study, Ni0.4Cu0.2Zn0.4LaxYxFe2−xO4 (x = 0.00 − 0.10) nanospinel ferrites (NSFs) were fabricated via an ultrasonic irradiation route. The creation of single phase of spinel nanoferrites ...(NSFs) was investigated by X-ray powder diffractometry (XRD) and selected area diffraction pattern (SAED). The cubic morphology of all samples was confirmed by scanning and transmission electron microscopies (SEM and TEM) respectively. The UV-Vis investigations provided the direct optical energy band gap values in a narrow photon energy interval of 1.87–1.92 eV. The 57Fe Mössbauer spectroscopy analysis explained that the hyperfine magnetic fields of Octahedral (Oh) and Tetrahedral (Td) sites decreased with substitution. The paramagnetic properties of NPs decrease with increase of content of doped ions. Investigations of magnetic properties reveal a superparamagnetic nature at 300 K and soft ferromagnetic trait at 10 K. The Ms (saturation magnetization) and Mr (remanence) decrease and the Hc (coercivity) increases slightly with La3+ and Y3+ substitution. The observed magnetic traits are deeply discussed in relation with the morphology, structure, magnetic moments and cation distributions. The microwave characterization of the prepared NSFs showed that, dissipation (i.e., absorption) of incoming microwave energy occurs at a single frequency, for each sample, lying between 7 and 10.5 GHz. The reflection losses (RL) at these frequencies range from −30 to −40 dB and the mechanism of which is explained in the framework of dipolar relaxation and spin rotation. The best microwave properties were obtained with a LaY concentration of x = 0.08 having an RL of −40 dB @ 10.5 GHz and an absorption bandwidth of 8.4 GHz @ −10 dB. With these high values of RL and absorbing bandwidth, LaY doped NiCuZn NSF products would be promising candidates for radar absorbing materials in the X-band.
Sr
0.8
Ni
0.2
Fe
12−2
x
Mo
x
O
19
(
x
≤
0.35
) nanohexaferrites (NHFs) were obtained by a sol–gel combustion route. The phase identification was performed through X-ray powder diffraction (XRD), ...transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). The morphological and chemical composition analyses were verified by scanning electron microscope (SEM) and energy dispersive X-rays (EDX), respectively. The crystallite size (D
XRD
) of all produced samples has been estimated between 31 and 56 nm. Magnetization versus applied magnetic field (M–H) measurements of different products were conducted at 300 K (room temperature, RT) and 10 K, and the results revealed their ferrimagnetic character. Undoped Sr
0.8
Ni
0.2
Fe
12
O
19
NHFs have the maximum magnetic parameters at both temperatures. 10 K magnetization data such as
M
S
(saturation magnetization),
M
r
(remnant magnetization),
n
B
(magneton number), and
H
C
(coercivity) belonging to Sr
0.8
Ni
0.2
Fe
12
O
19
NHFs are
M
S,max
= 99.6 emu/g,
M
r,max
= 48.2 emu/g,
n
B,max
= 18.83 μ
B
, and
H
C,max
= 3406 Oe, respectively. Moreover, the squareness ratio (SQR = M
r
/M
S
) is 0.489 at RT and 0.484 at 10 K. Those magnitudes assign the single-domain structure with uniaxial crystal anisotropy for this hexagonal product at both temperatures. Some magnetic parameters like coercivities (in a range of (286–475) Oe) and
M
r
(in a range of (7.8–14.1) emu/g) drop sharply due to the Mo
6+
doping process. Calculated SQR values are between 0.111 and 0.206, which indicate the multi-domain wall structure for NHFs at both temperatures. Undoped Sr
0.8
Ni
0.2
Fe
12
O
19
NHFs can be classified as magnetically hard materials, while Mo-doped samples can be classified as soft magnetic materials.
Structural, magnetic, and optical properties along with N2 absorption-desorption features of Sm3+–Dy3+ ions co-substituted BaSr hexaferrite microspheres (HFMSs) engineered through a hydrothermal gel ...approach were investigated. The microstructural and morphological features were examined by powder X-ray diffraction (XRD), surface area and pore size distribution (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), and transmission electron microscopy (TEM) techniques. Rietveld analysis proved the purity of products. The BET revealed a slight variation in textural characteristics with increasing Sm3+–Dy3+ substitution. The surface area (11–16 m2/g) exhibits a pore volume of ~0.07 cm3/g and average pore size distributions of 26.6 nm. The 300 K and 10 K field-dependent hysteresis loops were registered. Remanent magnetizations (Mr) and coercive fields (HC) are in a range of 29.15–34.05 emu/g and 1420–5391 Oe at 300 K, respectively. The estimated saturation magnetizations (Ms) vary between 53.22 emu/g and 71.08 emu/g, and magneton numbers (nB) are in a range of 10.51–13.93 μB. At 10 K, the Mr = 35.18–46.83 emu/g, HC = 1487–4760 Oe, Ms = 81.82–99.17 emu/g, and nB = 14.83–19.44 μB, which are greatly higher compared to room temperature. All magnetic parameters exhibit strong ferrimagnetic features of pristine Sr0·5Ba0·5Fe12O19 and Dy3+ and Sm3+ co-doped HFMSs at both temperatures. Squareness ratios (SQRs), which are very close to 0.50 assign the single domain uniaxially symmetric structured HFMSs. δM type of remanence plots was applied to specify the intensity and type of interparticle interactions as a function of the externally magnetic field, H. The Schuster-Kubelka-Munk theory provides to estimate direct energy band gaps (Eg). Undoped or co-doped HFMSs have a very narrow magnitude of Eg data between 1.795 and 1.865 eV depending on the couple ion concentrations.
Pure Fe3O4 NPs and Oleylamin (OAm) capped MnxFe1-xFe2O4 (MnxFe1-xFe2O4@OAm) (0.2 ≤ x ≤ 1.0) nanocomposites (NCs) were synthesized by the polyol route. Lattice parameter increases with increasing Mn2+ ...concentration, due to the respective larger ionic radius of Mn2+ ion compared with the Fe2+ ion. The VSM analyses revealed superparamagnetic characteristics of all samples. The extrapolated specific saturation magnetization (σs) values decreased from maximum 50.74 emu/g to minimum 15.34 emu/g by increasing Mn content. The particle size dependent Langevin function was applied to determine the magnetic particle dimensions (Dmag) between 9.10 nm and 21.50 nm. The observed magnetic moments of NPs and NCs are in range of (0.64–2.10) μB and significantly less than 4 μB of bulk Fe3O4. Magnetic anisotropy was determined as uniaxial and calculated effective anisotropy constants (Keff) are between 32.14 × 104 Erg/g and 8.71 × 104 Erg/g. The size dependent saturation magnetization suggests the existence of a magnetically dead layers around the magnetic cores for NCs between 0.72 nm and 1.29 nm. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Mn2+ substitution have been determined. Although, the Mössbauer spectra for the sample x = 0.2 is composed of ferromagnetic sextets, paramagnetic doublet is also formed for other samples. The percent diffuse reflectance spectroscopy (DR %) and Kubelka-Munk theory were used to specify the optical properties. The estimated optical band gap (Eg) values from Tauc plots are between 1.50 eV and 2.05 eV. Increasing Mn content in NCs increased the band gap at different magnitudes.
•MnxFe1-xFe2O4 (x = 0.2, 0.4, 0.6, 0.8 and 1.0) NPs were synthesized by polyol route.•The microstructure and average grain size of nanoparticles were determined from XRD, TEM and SEM.•The magnetic behavior was characterized using VSM and Mössbauer.•The main results are discussed in terms of cation distribution and microstructure.
This paper emphasizes the structure, morphology, optical, and magnetic properties of sonochemically prepared terbium-substituted cobalt ferrite nanoparticles, CoTbxFe2-xO4 (0.00 ≤ x ≤ 0.10). The ...formation of cubic spinel nanosized ferrite structure was confirmed by X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FT-IR) spectroscopy. The crystallites sizes were found in the range of 11–14 nm. Ultraviolet–visible percentage diffuse reflectance investigations were performed on pristine and Tb3+-doped cobalt spinel ferrite CoFe2O4 nanoparticles. The direct energy band gap (Eg) values were determined by applying the Kubelka–Munk theory and Tauc plots were found to be in a narrow band range of 1.37–1.44 eV. Analyses of magnetization versus the magnetic field (M(H)) were performed. The magnetic parameters, including the saturation magnetization (Ms), squareness ratio (SQR = Mr/Ms), magnetic moment (nB), remanence (Mr), and coercivity (Hc) were evaluated. The M(H) curves exhibited a soft ferrimagnetic nature. It was demonstrated that the Tb3+ substitutions strongly influenced the magnetization data. Indeed, the Ms, Mr, Hc, and nB values decreased with increasing Tb3+ substitution.
We have deposited five periodic SiO2/SiO2 +Ag multi-nano-layered films on fused silica substrates using physical vapor deposition technique. The co-deposited SiO2_Ag layers were 2.7-5nm and SiO2 ...buffer layers were 1-15nm thick. Total thickness was between 30 and 105nm. Different concentrations of Ag, ranging from 1.5 to 50molecular% with respect to SiO2 were deposited to determine relevant rates of nanocluster formation and occurrence of interaction between nanoclusters. Using interferometry as well as in situ thickness monitoring, we measured the thickness of the layers. The concentration of Ag in SiO2 was measured with Rutherford Backscattering Spectrometry (RBS). To nucleate Ag nanoclusters, 5MeV cross plane Si ion bombardments were performed with fluence varying between 51014 and 11016 ions/cm2 values. Optical absorption spectra were recorded in the range of 200-900nm in order to monitor the Ag nanocluster formation in the thin films. Thermal annealing treatment at different temperatures was applied as second method to form varying size of nanoclusters. The physical properties of formed super lattice were criticized for thermoelectric applications.
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