Fabrication of Nd-Ho Cosubstituted Co0.5Ni0.5Fe2O4 Nanospinel Ferrites and Exploration of Their Microstructure, Magnetic, and Electromagnetic Characteristics.

The composition and hyperfine structures of Nd3+-Ho3+ ions cosubstituted CoNi nanospinel ferrites (Co0.5Ni0.5NdxHoxFe2-2xO4 (x ≤ 0.05) NSFs) as well as their magnetic and electrodynamic behavior have been presented. The compound Nd-Ho → CoNiFe2O4 (x ≤ 0.05) NSFs were produced using the sol-gel method. XRD powder patterns indicated phase- and substituent-induced modifications of crystallites. The SEM analysis indicated the homogeneous distribution of grains with Nd-Ho cosubstitution. It was found that the values of x had an impact on the hyperfine magnetic field of the A and B sites. The cation distribution was determined by using Mössbauer spectroscopy. The M-H loops' investigations showed that the current NSFs behave ferrimagnetically at both room and low temperatures. An almost continuous rise in the strength of the coercive field was noticed with a rise in Ho-Nd content. The value of calculated squareness ratio values was above 0.5 at both temperatures, entailing that the studied NSFs' structure is made of single magnetic domains. The electromagnetic characteristics of the samples can be explained by the main contribution to electromagnetic absorption being the electric energy losses. Electromagnetic absorbed materials can be applied to provide electromagnetic compatibility and develop functional electromagnetic shields.

Interface-Charge Induced Giant Electrocaloric Effect in Lead Free Ferroelectric Thin-Film Bilayers.

Conventional refrigeration methods based on compression-expansion cycles of greenhouse gases are environmentally threatening and cannot be miniaturized. Electrocaloric effects driven by electric fields are especially well suited for implementation of built-in cooling in portable electronic devices. However, most known electrocaloric materials present poor cooling performances near room temperature, contain toxic substances, and require high electric fields. Here, we show that lead-free ferroelectric thin-film bilayers composed of (Bi0.5Na0.5)TiO3-BaTiO3 (BNBT) and Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BCZT) display unprecedentedly large electrocaloric effects of ∼23 K near room temperature under moderate electric bias. The giant electrocaloric effect observed in BNBT/BCZT bilayers, which largely surpasses the sum of the individual caloric responses measured in BNBT and BCZT, is originated from the presence of compositional bound charges at their interface. Our discovery of interface charge-induced giant electrocaloric effects indicates that multilayered oxide heterostructures hold tremendous promise for developing highly efficient and scalable solid-state cooling applications.

Control of the spatial distribution and crystal orientation of self-organized Au nanoparticles.

Ordered, two-dimensional, self-organized Au nanoparticles were fabricated using radiofrequency (RF) magnetron sputtering. The particles were uniformly spherical in shape and ultrafine in size (3-7 nm) and showed an ultrahigh density in the order of ∼10(12) inch(-2). A custom-developed sputtering apparatus that employs low sputtering power density and a minimized sputtering time (1 min) was used to markedly simplify the preparation conditions for Au nanoparticle fabrication. The spatial distribution of Au nanoparticles was rigorously controlled by placing a Ta interfacial layer between the Au nanoparticles and substrate as well as by post-annealing samples in an Ar atmosphere after the formation of Au nanoparticles. The interfacial layer and the post-annealing step caused approximately 40% of the Au nanoparticles on the substrate surface to orient in the (111) direction. This method was shown to produce ultrafine Au nanoparticles showing an ultrahigh surface density. The crystal orientation of the nanoparticles can be precisely controlled with respect to the substrate surface. Therefore, this technique promises to deliver tunable nanostructures for applications in the field of high-performance electronic devices.

Self-ignited high temperature synthesis and enhanced super-exchange interactions of Ho(3+)-Mn(2+)-Fe(3+)-O(2-) ferromagnetic nanoparticles.

The present work is focused on the effect of Fe(3+) replacement by rare earth-Ho(3+) ions and their influence on the properties of MnFe2O4 ferrite. The Ho(3+) substituted MnFe2O4 ferrite samples with chemical formula MnHoxFe2-xO4 were synthesized where substitution concentration of Ho(3+) was 0.0, 0.05, 0.1 and 0.15. The samples were synthesized by the self-ignited sol-gel method using the nitrates of the respective elements. Powder X-ray diffraction, transmission electron microscopy, infrared spectroscopy, vibrating sample magnetometer (VSM) and electrical measurements were employed to characterize the structural, magnetic and electrical properties of these ferrite nanoparticles. The cations distribution between the tetrahedral (A-site) and octahedral sites (B-site) has been estimated by XRD analysis. It is found that substitution of Ho(3+) ions favorably influenced the magnetic and electrical properties. Magnetic measurements were carried out at 77 and 300 K. Saturation magnetization and coercivity increased from 54.57 to 71.6 emu g(-1) and 172 to 766 Oe, respectively, with increasing the Ho(3+) substitution. The change in magnetic properties may be explained with the increase of A-O-B (FeA(3+)-O(2-)-HoB(3+)) super exchange interactions and the anisotropy constant. The electrical properties show that the pure sample has lower resistivity with respect to any Ho(3+) doped one. The conduction mechanism is used to interpret electrical measurements. Results of the presently investigated samples with enhanced saturation magnetization, coercivity and remanence ratio indicate that the Ho(3+) doped MnFe2O4 nanoparticles can be a useful candidate for the application in high density recording media.

Al3+ ions dependent structural and magnetic properties of Co-Ni nano-alloys.

Ferrite samples with a chemical formula Co0.5Ni0.5Al(x)Fe(2-x)O4 (where x = 0.0, 0.25, 0.5, 0.75 and 1.0) were synthesized by sol-gel auto-combustion method. The synthesized samples were annealed at 600 degrees C for 4 h. An analysis of X-ray diffraction (XRD) patterns reveals the formation of single phase cubic spinel structure. The lattice parameter decreased linearly with the increasing Al content x. Nano size of the powders were confirmed by the transmission electron micrographs (TEM). Particle size, bulk density decreased whereas specific surface area and porosity of the samples increased with the Al substitution. Cation distribution of constituent ions shows linear dependence of Al substitution. Based on the cation distribution obtained from XRD data, structural parameters such as lattice parameters, ionic radii of available sites and the oxygen parameter 'u' is calculated. Saturation magnetization (M(s)), magneton number (n(B)) and coercivity (H(c)) decreased with the Al substitution. Possible explanation for the observed structural and magnetic behavior with various Al content are discussed.

Interplay of Na Substitution in Magnetic Interaction and Photocatalytic Properties of Ca1-xNaxTi0.5Ta0.5O3 Perovskite Nanoparticles.

This research paper delves into the enhancement of wastewater treatment through the design and synthesis of advanced photocatalytic materials, focusing on the effects of sodium (Na) substitution in Ca1-xNaxTa0.5Ti0.5O3 perovskites. By employing various analytical techniques such as X-ray diffraction, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy and UV-vis spectroscopy, the study examines the transition of these perovskites from tetragonal to orthorhombic structures and observes a reduction in Ca content with Na substitution, which also favors the cubic phase formation and inhibits secondary phases. Significantly, magnetic property analysis uncovers an unexpected ferromagnetic ordering in these perovskites, including compositions traditionally viewed as non-magnetic. The photocatalytic tests reveal a significant improvement in degrading Rhodamine B dye under visible light, particularly in samples with higher Na levels, attributed to enhanced light absorption and efficient electron processes. The study highlights the optimal Na substitution level for peak photocatalytic performance, offering valuable insights into the complex interplay between structural, magnetic, and photocatalytic properties of these perovskites, and their potential in various applications, thereby contributing to the advancement of wastewater treatment technologies.

A thorough Investigation of Rare-Earth Dy3+ Substituted Cobalt-Chromium Ferrite and Its Magnetoelectric Nanocomposite.

The stoichiometric compositions of a ferrite system with a chemical formula CoCr0.5DyxFe1.5-xO4 where x = 0.0, 0.025, 0.05, 0.075 and 0.1 were prepared by the sol-gel auto-combustion method. The structural, morphological and magnetic properties were studied by the X-ray diffraction (XRD), infra-red spectroscopy (IR), scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. XRD analysis confirmed the cubic spinel structure of the prepared samples without the presence of any impurity and secondary phases. Selected area electron diffraction and IR measurements gives further confirmation to the XRD observations. Considering that strain mechanism, elastic properties and cation distribution play a major role for controlling the magnetic properties and therefore these properties were precisely evaluated through reliable methodologies such as XRD and IR data. The cation distribution was determined by the X-ray diffraction data which are further supported by the magnetization studies. Magnetoelectric properties of CoCr0.5DyxFe1.5-xO4 + BaTiO3 have also been investigated. The mechanisms involved are discussed in the manuscript.

Impact of Sm3+ and Er3+ Cations on the Structural, Optical, and Magnetic Traits of Spinel Cobalt Ferrite Nanoparticles: Comparison Investigation.

In this study, we investigated a comparison of the structure, morphology, optic, and magnetic (room temperature (RT)) features of Er3+ and Sm3+ codoped CoFe2O4 (CoErSm) nanospinel ferrite (NSFs) (x ≤ 0.05) synthesized via hydrothermal (H-CoErSm NSFs) and sonochemical (S-CoErSm NSFs) approaches. The formation of all products via both synthesis methods has been validated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), along with energy-dispersive X-ray (EDX) and transmission electron microscopy (TEM) techniques. The single phase of the spinel structure (except for the Hyd sample with x = 0.03) was evidenced by XRD analysis. The D XRD (crystallite size) values of H-CoErSm and S-CoErSm NSFs are in the 10-14.7 and 10-16 nm ranges, respectively. TEM analysis presented the cubic morphology of all products. A UV-visible percent diffuse reflectance (DR %) study was performed on all products, and E g (direct optical energy band gap) values varying in the 1.32-1.48 eV range were projected from the Tauc plots. The data of RT magnetization demonstrated that all prepared samples are ferromagnetic in nature. M-H data revealed that rising the contents of cosubstituent elements (Sm3+ and Er3+ ions) caused an increase in M s (saturation magnetization) and H c (coercive field) in comparison to pristine samples. Although concentration dependence is significant (x > 0.02), no strict regularity (roughly fluctuating) has been ruled out in M s values for doped samples prepared via the hydrothermal method. However, sonochemically prepared samples demonstrated that M s values increase with increasing x up to x = 0.04 and then decrease with the further rise in cosubstituent Sm3+ and Er3+ ions. The calculated values of M s and H c were found to be greater in H-CoErSm NSFs compared to those in S-CoErSm NSFs. The present investigation established that the distribution of cations and the variation in crystallite/particle sizes are efficient to control the intrinsic properties of all samples.

Interface-Driven Multiferroicity in Cubic BaTiO3-SrTiO3 Nanocomposites.

Perovskite multiferroics have drawn significant attention in the development of next-generation multifunctional electronic devices. However, the majority of existing multiferroics exhibit ferroelectric and ferromagnetic orderings only at low temperatures. Although interface engineering in complex oxide thin films has triggered many exotic room-temperature functionalities, the desired coupling of charge, spin, orbital and lattice degrees of freedom often imposes stringent requirements on deposition conditions, layer thickness and crystal orientation, greatly hindering their cost-effective large-scale applications. Herein, we report an interface-driven multiferroicity in low-cost and environmentally friendly bulk polycrystalline material, namely cubic BaTiO3-SrTiO3 nanocomposites which were fabricated through a simple, high-throughput solid-state reaction route. Interface reconstruction in the nanocomposites can be readily controlled by the processing conditions. Coexistence of room-temperature ferromagnetism and ferroelectricity, accompanying a robust magnetoelectric coupling in the nanocomposites, was confirmed both experimentally and theoretically. Our study explores the 'hidden treasure at the interface' by creating a playground in bulk perovskite oxides, enabling a broad range of applications that are challenging with thin films, such as low-power-consumption large-volume memory and magneto-optic spatial light modulator.

Dynamical magnetic behavior of anisotropic spinel-structured ferrite for GHz technologies.

We have fabricated a high quality magnetic Ni0.5Zn0.5Fe2O4 ferrite powder/polymer composite sheet consisting of common and environmentally friendly elements only. The sheet was then tested for its dynamic permeability by irradiating with electromagnetic waves with frequencies up to 50 GHz. Two different originally developed methods were used for the high-frequency permeability measurements, a short-circuited microstrip line method and a microstrip line-probe method. It is challenging to measure the dynamic permeability of magnetic thin films/sheets beyond 10 GHz because of the low response signal from these materials. However, the two methods produced essentially equivalent results. In the frequency dependent permeability profile, the maximum position of the profile, [Formula: see text], shifted towards higher frequencies upon increasing an applied (strong) static external magnetic field, [Formula: see text]. A linear relationship between [Formula: see text] and [Formula: see text] for the entire range of [Formula: see text] was observed even at small [Formula: see text]. In general, the spinel-structured Ni-based ferrites exhibit low magnetic anisotropy, but the present sample showed a uniaxial-anisotropic behavior in the parallel direction of the sheet. Our Ni0.5Zn0.5Fe2O4 powder/polymer composite sheet thus exhibits high performance at GHz frequencies, and should be applicable e.g. as an anisotropic electromagnetic wave-interference material.

TiO2-Doped Ni0.4Cu0.3Zn0.3Fe2O4 Nanoparticles for Enhanced Structural and Magnetic Properties.

TiO2 (0-10 wt %)-doped nanocrystalline Ni0.4Cu0.3Zn0.3Fe2O4 (Ni-Cu-Zn) ferrites were synthesized using the sol-gel route of synthesis. The cubic spinel structure of the ferrites having the Fd3m space group was revealed from the analysis of Rietveld refined X-ray diffraction (XRD) data. The secondary phase of TiO2 with a space group of I41/amd was observed within the ferrites with doping, x > 3 wt %. The values of lattice parameter were enhanced with the addition of TiO2 up to 5 wt % and reduced further for the highest experimental doping of 10 wt %. Field emission scanning electron microscopy (FESEM) images exhibit the spherical shape of the synthesized particles with some agglomeration, while the compositional purity of prepared ferrite samples was confirmed by energy-dispersive X-ray spectroscopy (EDX) and elemental mapping. The cubic spinel structure of the prepared ferrite sample was confirmed by the Raman and Fourier transform infrared (FTIR) spectra. UV-visible diffuse reflectance spectroscopy was utilized to study the optical properties of the ferrites. The value of band gap energy for the pristine sample was less than those of the doped samples, and there was a decrement in band gap energy values with an increase in TiO2 doping, which specifies the semiconducting nature of prepared ferrite samples. A magnetic study performed by means of a vibrating sample magnetometer (VSM) demonstrates that the values of saturation magnetization of the ferrites decrease with the addition of TiO2 content, and all investigated ferrites show the characteristics of soft magnetic materials at room temperature. The Mössbauer study confirms the decrease in the magnetic behavior of the doped ferrites due to the nonmagnetic secondary phase of TiO2.

Structural, Magnetic, and Mossbauer Parameters' Evaluation of Sonochemically Synthesized Rare Earth Er3+ and Y3+ Ions-Substituted Manganese-Zinc Nanospinel Ferrites.

The effect of Er3+ and Y3+ ion-co-substituted Mn0.5Zn0.5Er x Y x Fe2-2x O4 (MZErYF) (x ≤ 0.10) spinel nanoferrites (SNFs) prepared by a sonochemical approach was investigated. Surface and phase analyses were carried out using SEM, TEM, and XRD. Hyperfine parameters were determined by fitting room-temperature (RT) Mossbauer spectra. Magnetic field-dependent magnetization data unveiled the superparamagnetic nature at RT and ferrimagnetic nature at 10 K. RT saturation magnetization (M S) and calculated magnetic moments (n B) are 34.84 emu/g and 1.47 µB, respectively, and have indirect proportionalities with increasing ion content. M S and n B data have a similar trend at 10 K including remanent magnetizations (M r). The measured coercivities (H C) are between 250 and 415 Oe. The calculated squareness ratios are in the range of 0.152-0.321 for NPs and assign the multidomain nature for NPs at 10 K. The extracted effective magnetocrystalline constants (K eff) have an order of 104 erg/g except for Mn0.5Zn0.5Er0.10Y0.10Fe1.80O4 SNFs that has 3.37 × 105 erg/g. This sample exhibits the greatest magnetic hardness with the largest magnitude of H C = 415 Oe and an internal anisotropy field H a = 1288 Oe among all magnetically soft NPs.

Synthesis of Dy-Y co-substituted manganese­zinc spinel nanoferrites induced anti-bacterial and anti-cancer activities: Comparison between sonochemical and sol-gel auto-combustion methods.

This study described the beneficial properties of ultrasonic irradiation approach to synthesize the spinel-type Dy-Y co-substituted Mn-Zn nanospinel ferrites (NSFs). We have used two different approaches like citrate sol-gel combustion and ultrasonic irradiation routes to produced series of Mn0.5Zn0.5Fe2-2x(DyxYx)O4 (0.0 ≤ x ≤ 0.05) NSFs (DyY-MnZn NSFs). The structure and morphology of NSFs X-was examined by using XRD, EDX, SEM and TEM methods. We have found that spinel ferrites and hematite phase in DyY-MnZn NSFs produced by citrate sol-gel, while DyY-MnZn NSFs created by ultrasonic irradiation contain a pure phase of spinel ferrite. TEM analysis revealed the spherical nanoparticles with fairly uniform size. We have also analyzed the biological applications of DyY-MnZn NSFs prepared by both methods (ultrasonication and sol-gel) by examining their anti-cancer and anti-bacterial (Escherichia coli and Staphylococcus aureu) activities. We have found that both methods produced inhibitory actions on colon cancer cells (HCT-116) and bacterial cells, whereas, no inhibitory action was observed when examined on normal and non-cancerous cells (HEK-293).

Structural, mechanical, dielectric properties and magnetic interactions in Dy3+-substituted Co-Cu-Zn nanoferrites.

Sol-gel-synthesized Co-Cu-Zn ferrite nanoparticles diluted with Dy3+ ions were investigated in terms of their structural, morphological, elastic, magnetic and dielectric properties. X-ray diffraction patterns showed the formation of a single-phase cubic spinel structure. As the concentration of Dy3+ ions was increased, the lattice length gradually increased from 8.340 to 8.545 Å, obeying Vegard's law. The Williamson-Hall (W-H) method was employed to observe the change in the lattice strain. Crystallite size obtained from W-H plots followed a pattern similar to that observed using the Scherrer equation. The cation distribution suggested a strong preference of Dy3+ ions for the octahedral B site while Cu2+ and Fe3+ ions were distributed over both A and B sites. The microstructures of the samples were visualized using transmission electron microscopy. Mechanical properties such as stiffness constant, longitudinal and transverse wave velocities, Young's modulus, bulk modulus, rigidity modulus, Poisson's ratio and Debye temperature were investigated by acquiring infrared spectra recorded in the range of 300 to 800 cm-1. Replacement of Fe3+ ions with the strongly magnetic Dy3+ ions increased the saturation magnetization and coercivity. Dielectric constant increased with Dy3+ substitution but decreased with applied frequency.

Impact of Tm3+ and Tb3+ Rare Earth Cations Substitution on the Structure and Magnetic Parameters of Co-Ni Nanospinel Ferrite.

Tm-Tb co-substituted Co-Ni nanospinel ferrites (NSFs) as (Co0.5Ni0.5) [TmxTbxFe2-2x]O4 (x = 0.00-0.05) NSFs were attained via the ultrasound irradiation technique. The phase identification and morphologies of the NSFs were explored using X-rays diffraction (XRD), selected area electron diffraction (SAED), and transmission and scanning electronic microscopes (TEM and SEM). The magnetization measurements against the applied magnetic field (M-H) were made at 300 and 10 K with a vibrating sample magnetometer (VSM). The various prepared nanoparticles revealed a ferrimagnetic character at both 300 and 10 K. The saturation magnetization (Ms), the remanence (Mr), and magneton number (nB) were found to decrease upon the Tb-Tm substitution effect. On the other hand, the coercivity (Hc) was found to diminish with increasing x up to 0.03 and then begins to increase with further rising Tb-Tm content. The Hc values are in the range of 346.7-441.7 Oe at 300 K to 4044.4-5378.7 Oe at 10 K. The variations in magnetic parameters were described based on redistribution of cations, crystallites and/or grains size, canting effects, surface spins effects, super-exchange interaction strength, etc. The observed magnetic results indicated that the synthesized (Co0.5Ni0.5)[TmxTbxFe2-x]O4 NSFs could be considered as promising candidates to be used for room temperature magnetic applications and magnetic recording media.

Structural, optical and magnetic properties of Tm3+ substituted cobalt spinel ferrites synthesized via sonochemical approach.

Co-Tm nano-spinel ferrite with chemical formula CoTmxFe2-xO4 (0.0 ≤ x ≤ 0.08) NPs were prepared via sonochemical approach. X-ray powder diffraction patterns, microscopic images (SEM and TEM) and infrared spectra proved the formation of Co spinel ferrite. The effect of Tm3+ substituted on spinal structure was evaluated by lattice parameters, tetrahedral and octahedral bond length and cationic distribution. The band gap energy (Eg) of samples were estimated by performing UV-Vis percent diffuse reflectance (% DR) and applying the Kubelka-Munk theory. Eg values are in an interval between 1.33 eV and 1.64 eV. The analyses of magnetization were performed at room (300 K; RT) and low (10 K) temperatures. Different magnetic parameters including coercivity Hc, saturation magnetization Ms, remanence Mr, squareness ratio (SQR = Mr/Ms) and magnetic moment nB were deduced and discussed. The results showed superparamagnetic (SPM) nature at RT for x = 0.00 and 0.02 samples. However, the other products exhibit ferromagnetic (FM) nature. At 10 K, all synthesized NPs display FM behavior. An amazing increase in the magnitudes of Ms, Mr and Hc was observed at 10 K in comparison to RT, which is principally due to the reduced thermal fluctuations of magnetic moments at lower temperatures. The Tm3+ substitution affects considerably the magnetizations data. An enhancement in the Ms, Mr, and nB was detected on increasing the Tm3+ concentration. The SQR values at RT are found to be smaller than 0.5 postulating a single domain nature with uniaxial anisotropy for all produced ferrites. However, SQRs are in the range 0.66-0.76 at 10 K, suggesting the multi magnetic domain at low temperature, except the x = 0.02 product where the SQR = 0.47 indicating the single magnetic domain. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties.

Structural, magnetic, optical properties and cation distribution of nanosized Ni0.3Cu0.3Zn0.4TmxFe2-xO4 (0.0 ≤ x ≤ 0.10) spinel ferrites synthesized by ultrasound irradiation.

In this study, Tm3+ ion substituted NiCuZn nanospinel ferrites, Ni0.3Cu0.3Zn0.4TmxFe2-xO4 (0.0 ≤ x ≤ 0.10), have been synthesized sonochemically. The structural, spectroscopic, morphological, optic and magnetic investigation of the samples were done by X-ray powder diffractometry (XRD), Fourier transform infrared spectrophotometry (FT-IR), UV-Vis diffused reflectance (%DR) spectrophotometry, transmission and scanning electron microscopies (TEM and SEM) along with EDX, Vibrating sample magnetometry (VSM), respectively. The purity of prepared products were confirmed via XRD, FT-IR, EDX and elemental mapping analyses. The analyses of magnetization versus M(H) (applied magnetic field) were performed at 300 and 10 K. The following magnetic parameters like Ms (saturation magnetization), SQR = Mr/Ms (squareness ratio), nB(magnetic moment), Hc (coercivity) and Mr (remanence) have been discussed. M(H) loops revealed superparamagnetic property at RT and soft ferromagnetic nature at 10 K. It is showed that the Tm3+ substitutions significantly affect the magnetizations data. A decreasing trend in the Ms, Hc, Mr, and nB values was detected with Tm3+ substitution.

Structural, magnetic, optical properties and cation distribution of nanosized Co0.7Zn0.3TmxFe2-xO4 (0.0 ≤ x ≤ 0.04) spinel ferrites synthesized by ultrasonic irradiation.

This study expressed the influence of Tm substitution on the structural, optical and magnetic properties of Co-Zn spinel ferrites (Co0.7Zn0.3TmxFe2-xO4 (0.0 ≤ x ≤ 0.04)). The different compositions were synthesized by sonochemical method using Qsonica ultrasonic homogenizer, frequency: 20 kHz and power: 70 W for 60 min. XRD patterns proved the presence of single-phase spinel ferrites with crystallites size in the 8-10 nm range. Cation distribution approved the occupancy of octahedral (B) site by Tm. The morphology and the elements stoichiometry are obtainable through FE-SEM, EDX and elemental mapping. Optical band gap (Eg) values were estimated via DR % (percent diffuse reflectance) investigations and Kubelka-Munk theory. Tauc plots revealed that direct Eg values are ranging between 1.49 and 1.68 eV. The analyses of magnetization versus magnetic field, M(H), were performed. The following magnetic parameters like saturation magnetization Ms, squareness ratio (SQR = Mr/Ms), magnetic moment nB, coercivity Hc and remanence Mr have been evaluated. M(H) curves revealed the superparamagnetic (SP) at RT and ferromagnetic property at 10 K. It was showed that the Tm3+ substitutions significantly affect the magnetic properties of host spinel ferrites. An increasing trend in the Ms, Mr, Hc, and nB values was noticed for lower Tm3+ substitution content.

Sonochemical synthesis and physical properties of Co0.3Ni0.5Mn0.2EuxFe2-xO4 nano-spinel ferrites.

Nanoparticles (NPs) of composition Co0.3Ni0.5Mn0.2EuxFe2-xO4, where 0.00 ≤ x ≤ 0.10 (hereafter called CNMEuF) were synthesized by sonochemical approach using UZ SONOPULS HD 2070 ultrasonic homogenizer (frequency of 20 kHz and power of 70 W). As-synthesized samples were characterized thoroughly to determine the effects of europium ions (Eu3+) substitution on their structure, morphology and magnetic traits. Structural analyses of the synthesized NPs confirmed their high purity and crystalline cubic phases. Percent diffuse reflectance (%DR) data and Kubelka-Munk theory were exploited to evaluate the optical band gap energies of the studied CNMEuF NPs. Values of optical band gap energies obtained from the Tauc plots were observed in the range of 1.47-1.58 eV. The hysteresis loops (at room temperature and 10 K) of synthesized NPs were analyzed to determine their magnetic properties. These NPs disclosed superparamagnetic and hard ferrimagnetic character at room temperature and 10 K, respectively. With exception, the sample with x = 0.10 revealed soft ferrimagnetic behavior at 10 K. Eu3+ doping was shown to have significant influence on the structure and magnetic attributes of the proposed CNMEuF NPs. Values of various magnetic parameters of proposed compositions were reduced with the increase in Eu3+ dopant contents.

Au quantum dots engineered room temperature crystallization and magnetic anisotropy in CoFe2O4 thin films.

For the first time, this work presents a novel room temperature time-effective concept to manipulate the crystallization kinetics and magnetic responses of thin films grown on amorphous substrates. Conventionally, metal-induced crystallization is adopted to minimize the crystallization temperature of the upper-layer thin film. However, due to the limited surface area of the continuous metal under-layer, the degree of crystallization is insufficient and post-annealing is required. To expose a large surface area of the metal under-layer, we propose a simple and novel approach of using an Au nanodots array instead of a continuous metallic under-layer to obtain crystallization of upper-layer thin films. Spinel cobalt ferrite (CFO) thin film as a 'model' was deposited on an Au nano-dots array to realize this methodology. Our findings revealed that the addition of quantum-sized Au nano-dots as a metal under-layer dramatically enhanced the crystallization of the cobalt ferrite upper layer at room temperature. The appearance of major X-ray diffraction peaks with high intensity and well-defined crystallized lattice planes observed via transmission electron microscopy confirmed the crystallization of the CFO thin film deposited at room temperature on 4 nm-sized Au nano-dots. This crystallized CFO thin film exhibits 18-fold higher coercivity (Hc = 4150 Oe) and 4-fold higher saturation magnetization (Ms = 262 emu cm-3) compared to CFO deposited without the Au under-layer. The development of this novel concept of room-temperature crystallization without the aid of additives and solvents represents a crucial breakthrough that is highly significant for exploring the green and energy-efficient synthesis of a variety of oxide and metal thin films.