Search

The bandstructure of 〈110〉 silicon nano wires (SiNWs) with diameters (d) up to 6.1nm were studied using density functional theory. Three types of surface termination were investigated: H, F, and OH; all giving quantum confinement induced direct bandgaps in the investigated size range. Comparison of the calculated results to reported experimental values showed that trends in the bandstructure behaviour were well reproduced. By studying the relative decrease of global and local minima in the conduction band minimum with increasing d, it was possible to predict a direct-to-indirect bandgap transition at d=9.2, 9.5, and 11.4 nm for H, F, and OH terminated NWs, respectively. [ABSTRACT FROM AUTHOR]

We report a magnetic study on nanostructured (Fe79Mn21)1-xCux (0.00⩽x⩽0.30) alloys using static magnetic measurements. The alloys are mainly composed by an antiferromagnetic fcc phase and a disordered region that displays a spin-glass-like behavior. The interplay between the antiferromagnetic and magnetically disordered phases establishes an exchange anisotropy that gives rise to a loop shift at temperatures below the freezing temperature of moments belonging to the disordered region. The loop shift is more noticeable as the Cu content increases, which also enhances the spin-glass-like features. Further, in the x=0.30 alloy the alignment imposed by applied magnetic fields higher than 4 kOe prevail over the configuration determined by the frustration mechanism that characterizes the spin glass-like phase. [ABSTRACT FROM AUTHOR]

A combined magnetization and zero-field 59Co spin-echo nuclear magnetic resonance (NMR) study has been carried out on one member of a recently developed class of highly ordered mesoporous nanostructured materials, mesoporous Co3O4 (designated UCT-8, University of Connecticut, mesoporous materials). The material was synthesized using one-step soft-templating by an inverse micelles packing approach. Characterization of UCT-8 by powder x-ray diffraction and electron microscopy reveals that the mesostructure consists of random close-packed Co3O4 nanoparticles ≈12 nm in diameter. The N2 sorption isotherm for UCT-8, which is type IV with a type H1 hysteresis loop, yields a 134 m2/g BET surface area and a 7.7 nm BJH desorption pore diameter. The effect of heat treatment on the structure is discussed. The antiferromagnetic Co3O4 nanoparticles have a Néel temperature TN=27 K, somewhat lower than the bulk. A fit to the Curie-Weiss law over the temperature range 75K≤T≤300K yields an effective magnetic moment of μeff=4.36 μB for the Co2+ ions, indicative of some orbital contribution, and a Curie-Weiss temperature ϴ=-93.5 K, consistent with antiferromagnetic ordering. The inter-sublattice and intra-sublattice exchange constants for the Co2+ ions are J1/kB=(-)4.75K and J2/kB=(-)0.87 K, respectively, both corresponding to antiferromagnetic coupling. The presence of uncompensated surface spins is observed below TN with shifts in the hysteresis loops, i.e., an exchange-bias effect. The 59Co NMR spectrum for UCT-8, which is attributed to Co2+ ions at the tetrahedral A sites, is asymmetrically broadened with a peak at ≈55MHz (T=4.2 K). Since there is cubic symmetry at the A-sites, the broadening is indicative of a magnetic field distribution due to the uncompensated surface spins. The spectrum is consistent with antiferromagnetically ordered particles that are nanometer in size and single domain. [ABSTRACT FROM AUTHOR]

Ab initio calculations, based on the planewave pseudopotential method and the density functional theory, have been reported on the changes in the electronic and structural properties of short carbon atomic chains held rigidly between hydrogenated thin armchair graphene nanoribbons (Na-AGNR) of dimer line numbers Na = 4 and 5. We have considered chains of several lengths (n = 4-9 atoms) and with different forms of attachment with the AGNRs. It is found that odd-numbered chains are metallic in nature, with chemical bonding more like ... C==C==C==C... (as in cumulene). Even numbered chains show semiconductor structure when held between 4-AGNR and semi-metallic nature when held between 5-AGNR, in both cases characterized by chemical bonding more like ... C[Single_Bond]C=C[Single_Bond]C=C... (as in polyyne). [ABSTRACT FROM AUTHOR]

The electronic structure and magnetic characteristics of Klein graphene nanoribbons (KGNRs), as observed by Suenaga and Koshino [K. Suenaga and M. Koshino, Nature 468, 1088 (2010)], are investigated using first-principles calculations. We find three new characteristics induced by the Klein boundary. First, the localized edge states in the KGNRs have a ferromagnetic coupling rather than the antiferromagnetic coupling of the zigzag graphene nanoribbons (ZGNRs). Lieb's theorem is no longer applicable in the KGNRs. Second, the marginal single carbon adatom of the ZGNRs can destroy the edge states nearby. The edge states can recover if the length of the zigzag chains is equal to or greater than five times that of the lattice constant. Finally, we show that the pentagon-heptagon edge can be induced from the Klein boundary. [ABSTRACT FROM AUTHOR]

In this communication, we report the preparation and properties of nano-CoFe2O4 by gel combustion in presence of KCl and subsequent heat treatments. The products were characterized by X-ray diffraction, Infrared spectroscopy, and Mössbauer Spectroscopy. Spinel type structure with all Fe in 3+ oxidation states was confirmed from the XRD and Mossbauer spectroscopy. The average crystallite sizes of the studied samples were about 6 and 50 nm. Low temperature magnetic and dielectric properties of the samples were studied by superconducting quantum interference device magnetometry and ac-impedance spectroscopy. The field and temperature dependent magnetization studies indicated superparamagnetic nature for 6 nm sample and ferromagnetic nature for 50 nm sample. The temperature-dependent dielectric properties measured over a wide range of frequencies indicated an increasing trend of dielectric permittivity with the decrease in crystallite size. Variable range polaron hopping conduction was observed in both samples. [ABSTRACT FROM AUTHOR]

We investigate optical bistability (OB) behavior in an asymmetric three-coupled quantum well structure inside a unidirectional ring cavity. By controlling the assisting coherent driven field and the frequency detunings of the two control laser fields, we find that the appearance and disappearance of OB can easily be controlled by adjusting the positions of the dual electromagnetically induced transparency windows. Analysis in the dressed-state picture is also given. Our scheme may be used for building more efficient all-optical switches and logic-gate devices for optical computing and quantum information processing. [ABSTRACT FROM AUTHOR]

The evolution of the magnetization configurations in highly spin polarized La0.7Sr0.3MnO3 (LSMO) thin film elements (20-60 nm in thickness) as a function of external magnetic field and temperature is studied by direct magnetic imaging using x-ray magnetic circular dichroism photoemission electron microscopy. The sample structuring is done via a pre-patterning process using a Cr mask layer. The LSMO grows amorphous on the Cr layer for the 20 nm thick film but polycrystalline at larger thicknesses. Temperature dependent studies allow for a direct comparison of the properties of the strained and unstrained LSMO regions on a single sample and show that the polycrystalline areas exhibit a higher TC compared to the epitaxial areas. The single crystalline areas are largely magnetically decoupled from the matrix. The magnetic switching between domain states and domain wall spin structures is determined for LSMO ring elements of varying size and thickness. We find that the magnetic field values required to depin domain walls or to nucleate domains increase with decreasing ring width due to the increasing role of shape anisotropy and edge defects. Both transverse and vortex domain walls are stable spin configurations at room temperature and at zero field. In particular, we demonstrate that the desired domain wall type can be selected by applying an appropriate field sequence. [ABSTRACT FROM AUTHOR]

Highlights • Magnetic properties of GaAs:Mn nanostructures as a function of the Mn at. %. • Clusters role in the GaAs:Mn evolution from 2D to 3D growth mode. • AFM images showing directly the 2D to 3D transition in GaAs:Mn at high temperature. • Magnetic response of MnAs clusters related with GaAs:Mn surface structures. • Observation of an anomalous magnetic behavior related to confinement conditions. Abstract We report the influence of the Mn atomic concentration (at.%) on the nanostructures formation and magnetic properties of GaAs:Mn layers grown by Molecular Beam Epitaxy at a relatively high substrate temperature of 530 °C varying the nominal Mn at.% content from 0.01 to 0.2. It is shown that by modifying the Mn at.% different kind of nanostructures, ranging from 2D (such as islands and surface corrugation) to 3D microleave- and nanowire-like arrays, form on the surface layer. Samples produced with Mn contents ranging from 0.02 to 0.20 at.% show a significant room temperature ferromagnetic response that is attributed to the formation of MnAs nanocrystals as confirmed from X-ray diffraction analysis and magnetization measurements. The influence of MnAs clusters on the formation of the nanostructures observed is discussed. [ABSTRACT FROM AUTHOR]

We report a theoretical investigation on wave-vector filtering (WVF) effect in a magnetic nanostructure, which can be experimentally realized by depositing ferromagnetic (FM) stripes on the surface of GaAs/AlxGa1-xAs heterostructure. An appreciable WVF effect appears in this nanosystem. The WVF efficiency is associated with structural parameters of magnetic nanostructure. Therefore, such a device can be employed as a momentum filter for nanoelectronics device applications. [ABSTRACT FROM AUTHOR]

Manipulation of magnetic domain walls in nanostructures can be used to improve the capabilities of the next generation of memory and sensing devices. Materials of interest for such devices include heterostructures of ultrathin ferromagnets sandwiched between a heavy metal and an oxide, where spin–orbit coupling and broken inversion symmetry give rise to the Dzyaloshinskii-Moriya interaction (DMI), stabilizing chiral domain walls. The efficiency of the motion of these chiral domain walls may be controlled using in-plane magnetic fields. This property has been used both for measurement of DMI strength, and for improved performance in applications. While micromagnetic simulations are able to accurately predict domain wall motion under in-plane fields in these materials, collective coordinate models such as the q - ϕ and q - ϕ - χ models fail to reproduce the micromagnetic results. In this theoretical work, we present a set of extended collective coordinate models including canting in the domains, which better reproduce micromagnetic results, and improve our understanding of the effect of in-plane fields on magnetic domain walls. These models are used in conjunction with micromagnetic simulations to develop simpler descriptions of DW motion under specific conditions. Our new models and results help in the development of future domain wall based devices based on perpendicularly magnetized materials. [ABSTRACT FROM AUTHOR]

Abstract In this work erbium (Er3+) substituted cobalt zinc ferrite having general formula Co 0.70 Zn 0.30 Er x Fe 2-x O 4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were fabricated using micro-emulsion technique. The substitution of Er was done for the purpose of tuning the optical band gap. Er+3 substituted nanoparticles were annealed at 700 °C for 7 h. A typical composition of Co 0.70 Zn 0.30 Er x Fe 2-x O 4 was utilized to make the nanocomposites material with reduced graphene oxide (rGO), that was prepared by facile chemical route. The main purpose of graphene was to enhance the conductivity of ferrite particles. All these ferrite particles and a composite were characterized by X-rays diffraction (XRD), UV–Visible spectroscopy and SEM for structural elucidation and morphology studies. Single phase spinel structure was confirmed by XRD analysis and crystallized size calculated by Scherer formula was found in the range 35–60 nm. SEM confirmed the well dispersed ferrite particles among graphene sheets. All the Er-substituted ferrite particles were subjected to dielectric parameters study. One typical composition of Co 0.70 Zn 0.30 Er x Fe 2-x O 4 particles and its composites with rGO were utilized for photocatalysis study using methylene blue as model organic compound in the presence of visible light. Current-voltage (I-V) measurements of ferrites nanoparticles and their composites with graphene were also studied. The results of all these techniques were agreed with each other and suggested the various potential applications of these nanoparticles. Highlights • Rare earth Er3+-substituted Cobalt-Zinc Nano-ferrites were prepared. • XRD confirmed the FCC structure of all compositions. • Graphene@ ferrite composites exhibited better photocatalytic properties. [ABSTRACT FROM AUTHOR]

To make nanoparticles useful to fit various applications, the fundamental understanding of their magnetic and structural behavior is essential. A systematic in-depth study of the effect of field, temperature, and nanoparticles size on the critical points, and the magnetic properties of chemically synthesized Y2Fe17 nanoparticles have been performed. The blocking temperature varies with the change in the applied magnetic field as well as nanoparticles’ size variations. The Curie temperature was mostly influenced by particles’ size. Saturation magnetization and coercivity were shown to be temperature, size, and shape dependent. The results are significant and especially of interest in material science as they pave the path to a better understanding of different phenomena in nanomaterials in order for them to be used in diverse scientific applications. [ABSTRACT FROM AUTHOR]

Abstract Two-dimensional graphene oxide (GO) nanomaterials offer interesting physical/chemical properties and have been explored for potential use in electronics, magnetic, catalysis, and energy storage applications, because of its high charge-carrier mobility and high specific surface area. This study investigates the electronic and magnetic properties of nitrogenated graphene oxide (GO-N x), and nitrogenated graphene oxide functionalized with iron oxide (GO-N x :Fe). Four different nitrogen (N) precursor viz. ammonium hydroxide (NH 4 OH), hexamethylenetetramine (C 6 H 12 N 4), acetonitrile (C 2 H 3 N), and carbamide (CH 4 N 2 O) are used to synthesis " GO-N x " using chemical route. As C 6 H 12 N 4 based- GO-N x shows higher ferromagnetism, thus it is further functionalized with iron oxide using three different iron (Fe) precursors viz. ferric oxide (Fe 2 O 3), ferroso-ferric oxide (Fe 3 O 4), and iron oxide-hydroxide (FeOOH) to tune this room temperature ferromagnetism (RTFM). The electronic structure of " GO-N x " and " GO-N x :Fe " are characterized using C 1 s , O 1 s , N 1 s and Fe 2 p core-level X-ray photoelectron spectroscopy (XPS) and their corresponding magnetic behaviours are correlated with the SQUID-measured M-H loops. The magnetic moment changes due to the conversion and formation of different nitrogen bonded carbon along with the different phase of iron oxide. The tuning of magnetization in " GO-N x " and " GO-N x :Fe " using different N-precursors and/or Fe-precursors is an efficient route to tailor the electronic/magnetic properties of graphene-oxide for different electronic and magnetic device applications. Graphical abstract Unlabelled Image Highlights • Electronic and magnetic behaviours of GO-N x and GO-N x :Fe composites are studied. • For this study X-ray photoelectron spectroscopy, M-H hysteresis loops are used. • Magnetization of GO-N x :Fe composites is higher than GO-N x. [ABSTRACT FROM AUTHOR]

Polymeric hybrid materials were synthesized via chemical oxidation polymerization. Process was carried on the surface of the magnetic nanoparticles, (prepared separately) where the initiator (Fe 3+ ions) was located. The structure of the resulting nanocomposite was investigated in detail by means of X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The hydrodynamic size and morphology were evaluated by scanning electron microscopy (SEM) and dynamic light scattering (DLS). The polymeric shell was controlled, and investigated using TGA analysis together with TEM characterization. Magnetic properties of the PRHD@CoFe 2 O 4 hybrid nanomaterials were studied in a wide range of temperature and in fields up to 120 kOe. The magnetic properties were investigated to determine to what extent the PRHD shell separates magnetically the CoFe 2 O 4 nanoparticles and influences their properties. The cytotoxicity of the nanoparticles was tested against mouse macrophage (J774. E) and human osteosarcoma cell line (U2OS). Additionally, sensitivity of bacteria Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 25923 to hybrid materials was investigated using a of Kirby-Bauer disc method. [ABSTRACT FROM AUTHOR]

The current spintronic research focuses on lowering switching energy and maintaining good thermal stability of nanomagnets, which could ensure further development of memory technology. Here, we investigate a single-digit nanometer magnetic tunnel junction composed of self-assembled FePt nanopillars isolated by crystallized ZrO2. We find that the lateral size range of the operational device could be sub-7-nm by maintaining outstanding thermal stability. [ABSTRACT FROM AUTHOR]

Nanostructured Co 1-x Zn x Nd y Fe 2-y O 4 (0 ≤ x ≤ 1.0; y = 0.0 and 0.1) ferrites were synthesized through combustion route. All the compositions were irradiated with 60 Co gamma with total exposure dose 310 kGy at the dose rate 6.1kGy/h. The virgin and irradiated nanoparticles were characterized by the techniques; XRD, FTIR, SEM and EDAX. The DC electrical conductivity was measured in temperature range 300–800K. Magnetic parameters were measured with vibrating sample magnetometer (VSM) at 300K. Characterization studies reveal the structure, size, morphology and composition of the nanoferrites. The x-ray diffraction analysis revealed the cubic spinel ferrite structure. The characteristic feature of nanoferrites was confirmed by two prominent absorption bands ν 1 and ν 2 in the range 566–607 cm −1 and 401-498cm −1 . The SEM micrographs evidenced almost spherical shaped agglomerated grainy structure of nanoferries. DC conductivity studies revealed that Curie temperature (T C ) decreased with increasing Zn 2+ ion and Nd 3+ ion substitution due to the weakening of A–B interaction. The observed enhancement of DC conductivity and magnetic parameters on γ-irradiation attributed to the rearrangement of cations at A-site and B-site in the lattice. [ABSTRACT FROM AUTHOR]

In this paper, some of the electronic properties of GaN monolayer nanosheet are investigated in its pure form and after substitution of Cu and Se atoms. Electronic properties have been calculated based on the density functional theory approach with full-potential linearized augmented plane wave method. The results show that GaN nanosheet is a nonmagnetic semiconductor and its energy gap is equal to 2.202 eV. Our results show that GaN nanosheet properties vary with substitution of Cu or Se atoms: GaSeN and GaCuN show half-metallic and metallic behaviors, respectively. Calculated magnetic moments for GaSeN and GaCuN are 1.00 and 1.127 µB, respectively. [ABSTRACT FROM AUTHOR]

Magnetic Fe 2 O 3 /SBA-15 mesoporous nanomaterials were synthesized by means of a facile impregnation and calcination method. As-prepared magnetic nanomaterials were characterized using XRD, N 2 adsorption-desorption isotherms, SEM, TEM, VSM and XPS techniques. And the photocatalytic activities of magnetic Fe 2 O 3 /SBA-15 on the degradation of rhodamine B were also evaluated. Results indicate that the order structure of as-synthesized nanomaterials still remains, but its specific surface area, pore volume and pore size decrease. The saturation magnetization of the samples increases and its particle size decreases gradually with increasing the calcination temperature. And the existence of SBA-15 mesoporous molecular sieves increases largely the stability of γ-Fe 2 O 3 . Moreover, as-synthesized magnetic Fe 2 O 3 /SBA-15 shows high photocatalytic activities in the course of the degradation of rhodamine B by photo-Fenton-like reaction at natural pH about 6.3 and visible light irradiation. The structure and amount of catalyst, the concentration of H 2 O 2 and rhodamine B are main influence factors on the degradation of rhodamine B, and these influence results have been depicted quantitatively from dynamics. Rhodamine B in aqueous solution could almost be removed completely after a period of illumination by visible light and overnight in the dark. Meanwhile, as-prepared magnetic Fe 2 O 3 /SBA-15 has excellent reusability and stability, which its photocatalytic activity has only a slightly decrease after five consecutive runs. Therefore, as-synthesized magnetic Fe 2 O 3 /SBA-15 has a broad prospect of practical application. [ABSTRACT FROM AUTHOR]

Thin films of Zn 0.9 Co 0.1−x Ni x O (x = 0.0, 0.02, 0.04, 0.06, 0.08, 0.1) series were deposited by Pulsed Laser deposition technique (PLD) on a single crystal (100) silicon substrate. The structure of the films was confirmed as single phase hexagonal wurtzite structure by X-ray diffraction technique (XRD). The highest intensity peak was found at (002) plane. The surface morphology of thin films studied by Scanning Electron Microscope (SEM) depicted the high grain growth with definite boundaries. The room temperature resistivity measurements were carried out by four-point Probe methods which showed the semiconducting behavior of the thin films. Magnetic properties characterized by Vibrating Sample Magnetometer (VSM) at room temperature, exhibited the weak ferromagnetic or superparamagnetic behavior due to the alignment of the spins in the same direction around the oxygen vacancy and Co/Ni ions. Optical properties were observed by Spectroscopic Ellipsometry. The thickness of the films lied in 200–265 nm range and the bandgap energy was found to decrease from 3.09 to 3.03 eV confirming the inclusion of Ni a deep level impurity. [ABSTRACT FROM AUTHOR]

The magnetic domain state of carbon coated iron nanopowder (Fe@C) was studied by the internal field nuclear magnetic resonance (IFNMR) at 77 K using the spin echo technique. The structure and magnetic properties of the sample were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and Raman Spectroscopy. The obtained IFNMR results of Fe@C powder were compared with that of micron sized carbonyl iron (CI) and electrolytic iron (EI) powders. The calculated critical size of the single domain iron particles in Fe@C is ∼ 16 nm. A higher enhancement in echo amplitude was observed due to better response of the domain walls of multidomain particles in comparison to the single domain particles. The echo signal of CI and EI particles exhibit a single narrow intense peak corresponding to the domain walls, whereas Fe@C exhibits two low amplitude peaks at two different frequencies: a low frequency (46.6 MHz) peak corresponds to the response of the domain walls of the multidomain particles and the other high frequency (47.2 MHz) signal (a shoulder) corresponding to the response of the magnetic nuclei inside the domain. Our results help in determining the domain state of iron-based magnetic particles using 57 Fe-IFNMR. [ABSTRACT FROM AUTHOR]

Magnetic and ferroelectric properties in nanoscale are interesting topic to deal with. The primary interest is to understand the effect of simple, fast and cost effective sol gel method on the magnetic and electrical properties of Ba0.995Fe0.005Ti0.995Mn0.005O3 compounds. The study unravels the strategy for realizing multiferrocity of this composition by changing the processing temperature. Structural study confirms the infusion of Fe, Mn into the BaTiO3 lattice and its subsequent effects on the pseudo cubic and tetragonal phases. Morphological results manifest the formation of nanoparticles and evolution of grain growth upon increasing the processing temperature. Incorporation of Fe, Mn and its substantial effects on the various polymorphs of BaTiO3 is clearly portrayed by dielectric results. Room temperature ferroelectric measurements reveal the electric polarization in them. Magnetic measurements show an unusual high coercivity of 4000 Oe and its transformation to a completely paramagnetic behaviour with the subsequent changes in their phase. Thus, the pseudo cubic phase aids to retain the ferroelectric polarization with simultaneous presence of magnetic signature hints their possibility towards fruitful multi-functionality. [ABSTRACT FROM AUTHOR]

Nanostructures of complex oxides [BiFe x Mn 2−x O 5 (x = 0, 1, 2)] have been designed to study their structural, optical and magnetic behaviour. X-ray diffraction data (XRD) revealed orthorhombic phase with Pbam space group. Noticeable expansion in unit cell parameters has been found from BiMn 2 O 5 (x = 0) to BiFe 2 O 4.5 (x = 2). The observed structural changes via tuning of B-site (x = 0–2) played an important role in overall magnetic properties. Transmission electron microscopic images confirm that the average particle size of all the materials are in nano domain range with different morphologies. From optical studies, it has been found that the observed energy band gap values are strongly related to 3d electron numbers. These values appear to be larger than that reported for bulk. Isothermal magnetization plots (at 5 K) show increase in coercivity (H c ) from x = 0 to x = 2. Temperature dependent magnetization studies implied anti-ferromagnetic interactions for BiMn 2 O 5 , frustrated magnet for BiFeMnO 5 and ferromagnetic behaviour for BiFe 2 O 4.5 . Ferromagnetic state of nanostructured BiFe 2 O 4.5 is in contrast with its bulk counterparts. [ABSTRACT FROM AUTHOR]

Alloyed powders with combination of (Fe 67 Ni 33 ) 70 Ti 10 B 20 at different milling times are obtained. Structural, magnetic and thermal characterizations are performed by using X- ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, differential scanning calorimetry, transmission electron microscopy and vibrating sample magnetometer. It is indicated that the crystallite size is sharply decreases in the initial stage of milling process and the microstructure tends to nanocrystalline structure with increasing milling time. A rapid drop in saturation magnetization is observed after 48 h milling time, while coercivity value attains to a lowest value of about 33 Oe. Heat analysis of the milled sample at 120 h shows an endothermic peak. The coercivity of the 120 h annealed sample is increased as compared to the starting powders. [ABSTRACT FROM AUTHOR]

Ultrasound-assisted co-precipitation has been used to prepare nano-sized Ni0.4Cu0.2Zn0.4Fe2O4 ferrite. Continuous (C-US) and pulsed (P-US) ultrasound modes are used at constant frequency = 20 kHz, reaction time = 2 h and pulse durations of 10 s on and 10 s off. All experiments were conducted at two temperatures 90 and 100°C. Samples were characterized by X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR), N2 adsorption isotherms at 77 k analysis (BET), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM) techniques. A nanocrystalline single-phase with particle size in the range 12-18 nm is obtained in both modes: continuous and pulsed ultrasound mode. FT-IR measurements show two absorption bands assigned to the tetrahedral and octahedral vibrations (ν1 and ν2) characteristics of cubic spinel ferrite. The specific surface area (SBET) is in the range of 110-140 m2 g−1 and an average pore size between 5.5 and 6.5 nm. The lowest values are obtained in pulsed mode. Finally, this work shows that the magnetic properties are affected by the ultrasound conditions, without affecting the particle shape. The saturation magnetization (Ms) values obtained for all samples are comparable. In P-US mode, the saturation magnetization (Ms) increases as temperature increases. Moreover, P-US mode opens a new avenue for synthesis of NiCuZn ferrites. [ABSTRACT FROM AUTHOR]

Nanocrystalline cobalt ferrite CoFe2O4powders have been successfully synthesized via modified co-precipitation at low temperature. Obviously, well crystalline CoFe2O4phase was obtained from the precipitated precursors at pH 10 using 5 M NaOH as a base thermally treated at 80°C for 1 h in aqueous medium in the absence and the presence of 1000 ppm cetyl trimethyl ammonium bromide (CTAB) as well as sodium dodecyl sulfate (SDS) as cationic and anionic surfactants, respectively. Meanwhile, the spinel ferrite was observed with the similar conditions using ethylene glycol as an organic solvent. The microstructures of the formed powders exhibited nanospheres like structure with narrow size distribution from 6 to 10 nm. The magnetic properties of the formed cobalt ferrite powders strongly depend on the synthesis conditions. For instance, the highest saturation magnetization (Ms = 36.2 emu/g) was achieved in the aqueous medium, whereas the lowest saturation magnetization (Ms = 16.2 emu/g) was accomplished in the ethylene glycol medium. Indeed, heating properties of the CoFe2O4samples in an alternating magnetic field (AMF) at 160 kHz were estimated. Of note, it is clear that the specific heat rate SAR values were in the range from 104.5 to 302.0 W/g at different synthesis conditions, making co-ferrite appropriate for hyperthermia treatment of cancer. [ABSTRACT FROM AUTHOR]

BiFeO3 (BFO), Bi0.9Ho0.1FeO3 (BHFO), and transition metal (TM = Cr, Mn, Co, Ni, Cu, Zn) doped Bi0.9Ho0.1FeO3 (BHFO-TM) nanopowders were prepared by a double-solvent-based sol–gel route. The effects of Ho3+ and TM ion co-doping on the structural, morphological, optical, and magnetic properties of BFO nanopowders were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–Vis-NIR Spectrophotometer, and vibrating sample magnetometer. XRD patterns confirmed the distorted perovskite structure with R3c space group for all BHFO and BHFO-TM samples. TEM images identified that the particles of all BHFO and BHFO-TM samples were structured at the nanoscale (50 ~ 90 nm). BHFO-TM samples represented different visible light absorption and further decreased the band gap of BFO. The band gap of BHFO-Co nanoparticles (NPs) was the least (1.70 eV), which was a promising material for photocatalyst and photovoltaic devices. The magnetic tests indicated that BHFO-Cr in the BFO, BHFO, and BHFO-TM NPs samples had stronger ferromagnetic property with a small coercive magnetic field (Hc = 82 Oe), which is suitability for device applications. The mechanisms of the effects of Ho3+ and transition metal ion doping on optical and magnetic properties of BFO nanopowders were discussed in detail. [ABSTRACT FROM AUTHOR]

Colloidal hierarchical self-assembled Zn3V2O7(OH)2(H2O)2 superstructures, were synthesized via a simple and large-scale production route and then was converted into ZnV2O4 and Zn3V2O8 by calcination with retaining Zn3V2O7(OH)2(H2O)2 original morphology and hydrophilicity. Prepared compounds were characterized by X-ray diffraction, energy dispersive X-ray analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The optical, magnetic and photoluminescence properties of Zn3V2O7(OH)2(H2O)2, ZnV2O4 and Zn3V2O8 were explored by ultraviolet–visible spectroscopy, vibrating sample magnetometer and emission/excitation spectroscopy, respectively. According to the scanning electron and transmission electron microscopy results, the as-prepared samples were crystallized with a flower-like morphology for the optimized materials. The hierarchical self-assembled flower-like particles were composed of a large number of similar nanosheets with a thickness of 10–70 nm. The photophysical properties investigation of Zn3V2O7(OH)2·2H2O demonstrated that this sample has a wide band gap with photoabsorption ability only in the UV region. The magnetic properties of the ZnV2O4 nanostructures were evaluated, and results showed sample has a ferromagnetic behavior at room temperature. Finally, the optical study of the Zn3V2O8 nanostructure showed a very pronounced red-shifted PL emission for the two excitation wavelengths of 237 and 340 nm in their photoluminescence spectra. [ABSTRACT FROM AUTHOR]

Magnetic behavior of nanostructured mesoporous manganese oxide materials, designated UCT-1 and UCT-18, were studied using a combination of superconducting quantum interference device (SQUID) magnetometry and 55Mn zero-field spin-echo nuclear magnetic resonance (NMR). Curie-Weiss fits to the magnetic susceptibility for the UCT-1 and UCT-18 samples calcined at 550 °C yielded paramagnetic moment values consistent with spin-only Mn3+ ions in the α-Mn2O3 phase (S = 2, 4.90 μB). However, the magnetization and NMR results reported here clearly identify a small amount of the Mn3O4 second phase (ferrimagnetic with TC ≈ 43 K) that does not appear in X-ray diffraction (XRD). The study resulted in the observation of fascinating magnetic behavior: (1) exchange bias, which occurs in cases where a ferromagnetic (or ferrimagnetic) phase forms a boundary with an antiferromagnetic phase and (2) a magnetic contribution attributed to uncompensated spins on the surfaces of the α-Mn2O3 nanoparticles. The presence of Mn3O4 and the interplay of Mn3+ and Mn2+ impact the catalytic properties. [ABSTRACT FROM AUTHOR]

The magnetic properties of the h-BN monolayer with nonmetal atoms are studied by ab initio methods. Different dopants (C, Cl, F, and O) and doping sites are considered. Magnetic behavior is observed in the two-dimensional (2D) BN system with C, Cl, and O atoms. On the other hand, the O adsorbed system shows a more stable formed structure among above three magnetic materials, we study the ferromagnetic (FM) interaction in 2D-BN system with two O adatoms. Interestingly, as the O-O distance increases, the interaction between two O adatoms prefers to a long-range FM coupling. This phenomenon could be well described by a simple Heisenberg model. [ABSTRACT FROM AUTHOR]

Shape-memory composites based on a commercial segmented polyurethane and magnetite (Fe 3 O 4 ) nanoparticles (NPs) were prepared by a simple suspension casting method. The properties of the resulting nanocomposites, containing 1 to 10 nominal wt.% magnetic particles, were evaluated by thermogravimetric tests, contact angle measurements, differential scanning calorimetry, infrared and X-ray spectroscopy, static and thermal cyclic tensile tests, dynamic mechanical analysis and experiments of alternating-magnetic-field heating. It was found that most of the suspended NPs could be successfully incorporated into the polyurethane matrix, and thus composite samples with up to 7 wt.% actual concentration were obtained. On the other hand, the incorporation of magnetite nanoparticles to the shape memory polyurethane did not significantly affect most of the matrix properties, including its shape memory behavior, while added magnetic response to the nanocomposites. Thus, nanocomposites were able to increase their temperature when exposed to an alternating magnetic field, which allowed them to recover their original shape quickly by an indirect triggering method. [ABSTRACT FROM AUTHOR]

The study of the magnetic properties of DyNi 4 Si nanostructures is of great interest to researchers due to the magnetic properties that can be tailored and altered to enhance the magnetocaloric effects. In the present work, using Monte Carlo and ab initio calculations we present an important advancement toward controlling the magnetocaloric proprieties of nanostructured DyNi4Si via size engineering, with important implications for magnetic refrigeration applications. The results show that magnetic and magnetocaloric properties correlate with the size and morphology effects (0D, 1D and 2D). [ABSTRACT FROM AUTHOR]

Abstract: This work presents the synthesis of iron oxide nanocatalysts supported on mesoporous Al‐SBA‐15 by using a continuous‐flow setup. The magnetic nanomaterials were tested as catalysts in the oxidative disruption of isoeugenol by using hydrogen peroxide as a green oxidant, featuring high activities (63–88 % conversion) and good selectivities to vanillin (44–68 %). The catalytic systems exhibited good magnetic properties when synthesized under continuous‐flow conditions at temperatures not exceeding 190 °C. The use of microwave irradiation significantly reduced times of reaction drastically but exerted negative effects on catalyst reusability. [ABSTRACT FROM AUTHOR]

Cobalt oxide nanostructures have been prepared using ultrasound waves by adding different concentrations of oleic acid as a capping agent. Cobalt oxide nanostructures were characterized using different techniques such as scanning electron microscopy, vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), UV-Vis, and FT-IR spectroscopy. The XRD patterns shows formation of pure cobalt oxide compounds in cubic structure. UV-Vis spectroscopy showed that by increasing the concentration of capping agent, the wavelength of absorption edge of the samples shifted toward blue region of the spectrum. The obtained results from VSM, indicated that the variation of magnetic susceptibility increased or decreased with concentration of oleic acid. [ABSTRACT FROM AUTHOR]

Ferrites are large class of oxides with astonishing magnetic properties, which have been investigated and applied for the past 50 years. Their applications range from millimeter wave integrated circuitry to magnetic recording & microwave devices. These applications are based on very basic properties of ferrites; such as significant saturation magnetization, high electrical resistivity, low electrical losses, and good chemical stability. Ferrites can be obtained in different crystal systems by many methods, and the feasibility in preparation opens the means to tailor their properties for many applications. By reducing the scale to the Nanometric size, new and technologically interesting properties have been obtained. In the current study, Structural and Magnetic properties of Aluminium substituted calcium hexaferrites are reported. A series of Aluminium substituted Calcium hexaferrite samples, have been prepared by Solution combustion synthesis. XRD patterns confirmed the formation of Hexagonal phase with space group P6 3 /mmc. Lattice parameter values decreased with Al 3+ content. Magnetic properties such as saturation magnetization (M s ), remanence (M r ) and magneton number (n B ) were found to decrease, while the coercivity (H c ) and reduced remanence (M r /M s ) of the samples were found to increase with increasing Al 3+ content. Results of VSM studies show the decrease in saturation magnetization with increase in Al concentration. However, the coercivity and Retentivity increased with Al concentration. The high values of retentivity and coercivity make these materials best for high-density recording media and permanent magnets. Our work suggests that, substitution can be used to alter magnetic property. This is the encroachment for selecting suitable materials for various technological applications. [ABSTRACT FROM AUTHOR]

Polycrystalline ferrites with general formula Ni x Mg 1-x Fe 2 O 4 (0.0 ≤ x≤ 0.5) were synthesized by solid state reaction method. The existence of cubic spinel structure of ferrites was confirmed by X-ray diffraction (XRD) measurement which belongs to the space group of Fd 3m - O h 7 . Crystallite size of ferrites was estimated by using Debye-Scherer formula; it varies from 930 nm to 1.04 μm. The lattice constant, interplanar distances and miller indices were estimated by using X-ray diffraction measurement. The lattice constant increases with increase in Ni content. Porosity of ferrites was estimated by using Hendricks and Adams method; it is found to increase with increase in Ni content and maximum porosity 22.4% was observed for Ni 0.5 Mg 0.5 Fe 2 O 4 ferrites. The dielectric constant decreases with increase in frequency shows dielectric dispersion behavior which is predicted by Maxwell-Wagner type interfacial polarization and is in good agreement with Koops phenomenological theory. AC conductivity increases with increase in frequency shows small polarons type of conduction mechanism. The magnetic properties of ferrites were studied by using M-H hysteresis loop and measured saturation magnetization and magnetic moment of the ferrites. [ABSTRACT FROM AUTHOR]

Nanograined Ni-Co alloys with controlled composition were prepared by co-precipitate assisted hydrogen reducing method, and their crystal structure, morphology and magnetic properties were obtained. Effect of the Co content on magnetic properties of the Ni-Co alloy was discussed. Results show that the saturation magnetization increases with higher Co content, which reaches to 214.70emu/g when the Co content is 90%. The coercivity increases with increasing in the Co content to 70%, and then it decreases as the Co content further increases. The research reveals that the saturation magnetization is affected by the atomic magnetism moment and the magnitude of coercivity is affected by both the Co content and the grain size. [ABSTRACT FROM AUTHOR]

In this work, cobalt micro-particles containing various nanoscale subunits were hydro- thermally synthesized and controlled by the content of sodium tartrate in reaction solution. Both the static and dynamic magnetization properties of cobalt particles changes accordingly. As the content of sodium tartrate varies from 0 g, 0.552 g to 4.416 g, subunits of the cobalt particles shrinks from dendrites, coralloids to small bumps, saturation magnetization changes from 122.5 emu/g, 86.5 emu/g, to 95.79 emu/g, and the coercive force reduces from 195 Oe, 148 Oe, to 62 Oe. Consequently, ferromagnetic resonance bandwidth of the cobalt particles decreases due to the diminishing surface scatterers (subunits), whereas low frequency loss tangential increases following the growth of spherical particle core. The proposed cobalt particles with nanoscale subunits shows potential for electromagnetic wave absorption and shielding application. [ABSTRACT FROM AUTHOR]

The magnetic properties of a Mn-doped armchair ZnO nanotube have been studied using Monte Carlo simulation. The variation of zero-field-cooled and field-cooled magnetisation with reduced temperatures for different values of the dilution x (where x is the Mn concentration: Zn1−xMnxO) are given. The freezing temperatures and magnetisation vs. crystal field are calculated for different dilutions x. Finally, the hysteresis loops for different dilutions and temperatures are given for a fixed reduced temperature and crystal field. Superparamagnetic behaviour is observed for small values of x and low temperatures. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, we investigate the evolution of electronic and magnetic properties of zigzag silicene nanoribbon (ZSiNR) along with the concentration of edge adsorbed hydrogen adatoms. Our study shows that the significant covalent bonding helps to stabilize the configurations of hydrogen adsorbed ZSiNRs. The ferro-metallic electronic property of ZSiNR originated from the σ-π mixing effect is suppressed by mono-hydrogenation at the adsorption sites due to the sp 2 bonding. However, bi-hydrogenation at the adsorbed sites will lead to the typical sp 3 bonding, which dominates the electronic property with the increasing of hydrogen adatoms. Under the coexisting situation with mono-hydrogenation and bi-hydrogenation, we find that both the number of adsorption sites and the bonding type of sp 2 or sp 3 have impact on the electronic property of ZSiNR. It is found that symmetry adsorption at the edges changes the stable magnetic state of ZSiNR from ferromagnetic to antiferromagnetic. In contrast, unsymmetrical adsorption along the two edges of ZSiNR keeps its ferromagnetic property. [ABSTRACT FROM AUTHOR]

Development of the interpretation of the phenomenon of the lift of the magnetic resonance frequencies degeneracy caused by the magnetostatic interaction in assemblies of nanodisks has been done. The difference of the resonance behavior of magnetic vortexes in a round and rectangular nanodots has been studied experimentally and explained. [ABSTRACT FROM AUTHOR]

For more than twenty years, nanotechnologies have arisen a huge interest and are used in numerous fields. Carbon nanotubes (CNTs) are one of the most used nanomaterials thanks to their excellent optical, mechanical, electrical and thermal properties. All along their lifecycle, CNTs may be spread in the environment during production, use, destruction, reuse or potential accidents in production units or during transportation. For this reason, it is essential to evaluate their behaviour and potential impacts on ecosystems and particularly on the terrestrial ecosystem. After a brief summary of CNT properties, synthesis methods, and applications as well as detection and characterisation techniques, this review will focus on impacts of CNTs on the terrestrial ecosystem, discussing their behaviour in soil, plants and interactions with other pollutants as well as their impacts on soil microbiota, macrobiota and plants. [ABSTRACT FROM AUTHOR]

The magnetization dynamics of single multilayer rhomboid shaped nanomagnets is investigated using micro-focused Brillouin light scattering spectroscopy. The nanomagnets consist of two permalloy layers separated by a nonmagnetic Cr spacer layer. By varying the Cr thickness in the range from 0 to 15 nm, the dipolar coupling is effectively controlled, thus modifying the corresponding magnetic ground states. The magnetization dynamics as a function of initialization field orientation has been systematically investigated. A significant tunable frequency difference of ~2 GHz in the microwave absorption between ferromagnetic and antiferromagnetic ground states is observed as the size of nanomagnets is varied. Micromagnetic simulations validate our experimental observations. [ABSTRACT FROM AUTHOR]

Considerably different properties emerge in nanomaterials as a result of quantum confinement and edge effects. In this study, the electronic and magnetic properties of quasi zero-dimensional silicene nanoflakes (SiNFs) are investigated using density functional theory (DFT) calculations. While the zigzag-edged hexagonal SiNFs exhibit non-magnetic semiconducting character, the zigzag-edged triangular SiNFs are magnetic semiconductors. One effective method of harnessing the properties of silicene is hydrogenation owing to its reversibility and controllability. From bare SiNFs to half-hydrogenated and then to fully hydrogenated, a triangular SiNF experiences a change from ferrimagnetic to very strong ferromagnetic, and then to non-magnetic. Nonetheless, a hexagonal SiNF undergoes a transfer from non-magnetic to very strong ferromagnetic, then to non-magnetic. The half-hydrogenated SiNFs produce a large spin moment that is directly proportional to the square of the flake’s size. It has been revealed that the strongly induced spin magnetizations align parallel and demonstrates a collective character by large range ferromagnetic exchange coupling, giving rise to its potential use in spintronic circuit devices. Spin switch models are offered as an example of one of the potential applications of SiNFs in tuning the transport properties by controlling the hydrogen coverage. [ABSTRACT FROM AUTHOR]

The results of investigation of colossal magnetoresistance relaxation in nanostructured La-Sr(Ca)-Mn-O films upon removal of magnetic field pulse are presented. Thin films having thicknesses of 75–350 nm grown by pulsed injection metal–organic chemical vapor deposition technique were studied in pulsed magnetic fields having duration of 0.9 ms and amplitudes of 2–12 T. It was obtained that “fast” relaxation process occurring in hundred microseconds time scale exhibits anisotropy: the magnitude of remnant resistivity is approximately three times smaller and the process is faster when magnetic field is applied perpendicular to the film plane in comparison with in-plane direction. The dynamics of this relaxation process was analyzed using Kolmogorov–Avrami–Fatuzzo model, taking into account nucleation and reorientation of magnetic domains into equilibrium state. The “fast” remnant relaxation was not observed after the application of longer pulses (20 ms) having amplitude of 60 T. Influence of remnant relaxation on operation of B-scalar magnetic field sensors based on nanostructured manganite films is discussed. [ABSTRACT FROM PUBLISHER]

Purpose of present article is to analyze the flow of Maxwell nanomaterial bounded by a nonlinear stretching sheet. Brownian motion and thermophoresis are discussed. Stretching sheet of variable thickness is considered. Electrically conducting fluid is entertained. The governing nonlinear problems are successively solved and addressed for the outcome of influential variables. The velocity of the fluid decreases by enhancing Deborah number effect while temperature and concentration have reverse effects. Temperature and concentration of the nanofluid are increasing functions of thermophoresis parameter. Concentration of nanoparticles decreases by increasing Brownian motion. Comparison of homotopy analysis and numerical solutions is tabulated. There is reasonable agreement between the results. [ABSTRACT FROM AUTHOR]

Nanostructure Pr 0.5 Sr 0.5 MnO 3 compounds were elaborated by mechanical milling in a planetary high energy ball mill at various milling times followed by high temperature sintering under air at 1400 °C for 20 h. The phase structure, the morphology, the magnetic and magnetocaloric properties of the powders were characterized by X-ray diffractometry, scanning electron microscopy and a vibrating sample magnetometer. Rietveld refinement of the X-ray diffraction patterns shows that all specimens crystallize in the tetragonal system with I4 /mcm space group. Increasing the milling time up to 16 h, the average crystallites size decreases to the nanoscale (∼36 nm). During the intermediate stage of milling, significant changes occur in the morphology of the powder particles, due to the severe plastic deformation. Significant refinement in particle size was found evident at the final stage of milling (∼2 µm). From magnetic measurements, it was found that all samples present two magnetic transitions as a function of temperature. The Curie temperature T C decreases with increasing milling time. Moreover, it was revealed that the antiferromagnetic domains fractions highly dependent on crystallites sizes. A large magnetocaloric effect and an important value of the relative cooling power around Neel temperature was observed in all samples. These characteristics may be related to the first-ordered nature of this transition. Moreover, the magnetic entropy change and the relative cooling power were increased with decreasing crystallites sizes. [ABSTRACT FROM AUTHOR]

In this work, electron paramagnetic resonance (EPR) experiment on undoped ZnO and Al doped ZnO (AZO) nanoparticles prepared by facile sol–gel method were investigated. The effects of the Al concentration on room temperature ferromagnetic (FM) properties of the AZO ( Zn 1 - x Al x O , 0.1 ⩽ x ⩽ 0.30 ) are reported. EPR signal reveals the origin of FM is purely intrinsic and related with interaction of clusters carrying net magnetic moment coming from electron spin trapped in defect states. Increasing Al concentration results in reducing FM ordering which are likely due to reduction in amount of oxygen adsorption. Defect analysis based on PL, indicates zinc interstitials ( Zn i ) and singly oxygen vacancies ( Vo + ) are responsible for mediating ferromagnetism in the undoped ZnO. The assertion was supported by Raman spectra and EPR analysis. Moreover, the present work suggests the potential applications of AZO in future spintronics and speculate the origin of ferromagnetism in AZO nanoparticles. [ABSTRACT FROM AUTHOR]

Nanostructures with open shell transition metal or molecular constituents host often strong electronic correlations and are highly sensitive to atomistic material details. This tutorial review discusses method developments and applications of theoretical approaches for the realistic description of the electronic and magnetic properties of nanostructures with correlated electrons. First, the implementation of a flexible interface between density functional theory and a variant of dynamical mean field theory (DMFT) highly suitable for the simulation of complex correlated structures is explained and illustrated. On the DMFT side, this interface is largely based on recent developments of quantum Monte Carlo and exact diagonalization techniques allowing for efficient descriptions of general four fermion Coulomb interactions, reduced symmetries and spin-orbit coupling, which are explained here. With the examples of the Cr (001) surfaces, magnetic adatoms, and molecular systems it is shown how the interplay of Hubbard U and Hund's J determines charge and spin fluctuations and how these interactions drive different sorts of correlation effects in nanosystems. Non-local interactions and correlations present a particular challenge for the theory of low dimensional systems. We present our method developments addressing these two challenges, i.e., advancements of the dynamical vertex approximation and a combination of the constrained random phase approximation with continuum medium theories. We demonstrate how non-local interaction and correlation phenomena are controlled not only by dimensionality but also by coupling to the environment which is typically important for determining the physics of nanosystems. [ABSTRACT FROM AUTHOR]

A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho 3+ ) lithium ferrites; Li 1.2 Co 0.4 Ho x Fe 2−x O 4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO 3 ) were appeared for x ≥ 0.06 indicating the solubility limit of Ho 3+ ions. The lattice constant ′ a′ increased from 8.351 to 8.360 Å upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 Å. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho 3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho 3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral ( v 1 ) and octahedral ( v 2 ) intrinsic vibrational bands at 627 cm −1 and 479 cm −1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants ( K o and K t ) were calculated and discussed with the tetrahedral (r A ) and octahedral (r B ) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 10 3 to 5.56 × 10 4 (Ω-cm) −1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho 3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li 1.2 Co 0.4 Ho 0.12 Fe 1.88 O 4 . The improved coercivity may suggest their utilization in perpendicular recording media applications. [ABSTRACT FROM AUTHOR]