Room Temperature Magnetic Measurements Research Articles

Hydrothermally Synthesized Mg-Based Spinel Nanoferrites: Phase Formation and Study on Magnetic Features and Microwave Characteristics

Three kinds of magnesium-based spinel nanoferrites with the chemical formulas of MgFe2O4 (Mg ferrite), Mg0.9Mn0.1Fe2O4 (Mg-Mn ferrite), and Mg0.9Mn0.1In0.1Fe1.9O4 (Mg-Mn-In ferrite) were synthesized by hydrothermal route. We report the composition-dependent magnetic parameters and microwave properties of Mg-based ferrite nanoparticles. XRD results revealed that the Mg-based ferrite nanoparticles exhibited a cubic spinel structure and had an average nanocrystallite size in the range of 5.8–2.6 nm. Raman spectroscopy analysis confirmed the formation of cubic-spinel phase Mg-based nanoferrites. The room-temperature magnetization measurements indicated that the Mg ferrite nanoparticles had superparamagnetic behavior; whereas the Mg-Mn and Mg-Mn-In ferrite nanoparticles exhibited a paramagnetic nature. The microwave properties of obtained ferrite nanoparticles were studied by alternating current (AC) magnetic susceptibility measurement and electron paramagnetic resonance (EPR) spectroscopy. It was found that the un-substituted Mg ferrite sample exhibited microwave characteristics better than those of the Mn substituted and Mn-In co-substituted Mg ferrite samples.

Effects of Fe substitution on structural, electrical and magnetic properties of Erbium ortho-chromite nano polycrystalline material

Abstract Perovskite ErCr1−xFexO3 polycrystalline samples at nanoscale were synthesized using sol-gel auto-combustion process. The structural studies confirmed that except for x = 1.0, all the other samples, exhibited single-phase orthorhombic symmetry. The impedance data was collected in the frequency range of 1 Hz–1 MHz, and in the temperature range of 27–600 °C. Room temperature magnetic measurements were performed under maximum applied field of upto 10 kOe. All the samples, except for x = 1.0 exhibited giant dielectric behaviour (>103) in the low frequency region at room temperature due to the grain boundary effects (Maxwell-Wogner polarization). Impendence measurements for all the samples indicated the existence of negative temperature coefficient of resistance and non-Debye behaviour. Magnetic hysteresis studies demonstrated a weak ferromagnetic nature for all the samples, except for x = 1.0 and for x = 1.0, anti-ferromagnetic behaviour was noticed.

Interlayer strain effects on the structural behavior of BiFeO3/LaFeO3 superlattices

Artificial (BiFeO3)0.5Λ/(LaFeO3)0.5Λ superlattices have been grown by pulsed laser deposition. The periodicity Λ was varied from 150 Å to 25 Å and the relative ratio between BiFeO3 (BFO) and LaFeO3 (LFO) is kept constant in each period. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy investigations indicate antiferroelectric-like structures for large periodicity (Λ ≥ 76 Å), while Pnma LaFeO3-like structures are observed for small periodicity Λ ≤ 50 Å. Room temperature magnetic measurements were obtained by vibrating sample magnetometry and suggest antiferromagnetic ordering with weak ferromagnetism. Temperature dependent x-ray diffraction studies show an important shift of paraelectric-antiferroelectric phase transition scaling with BFO thickness. Strain and size effects explain this behavior and discussion is also made on the possible role of the oxygen octahedral rotation/tilt degree of freedom.

Influences of Oxygen Partial Pressure on the Cu Metal Clustering and Room Ferromagnetism of the (In0.89Fe0.06Cu0.05)2O3 Films

The influences of oxygen partial pressure on the local structure, magnetic, and transport properties of (In0.89Fe0.06Cu0.05)2O3 films deposited by different Ar–O2 flow rate (10:0, 10:0.4, and 10:3.0) were studied systematically by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), Hall effect, room temperature (RT) magnetic measurements, and first-principles calculations. The detailed structural analyses indicate that the doped Fe atoms substitute for In3+ sites of the In2O3 lattices with +2 and +3 mixture valences for all the films. However, the majority of codoped Cu atoms form the Cu metal clusters in the film deposited at oxygen flow rate of 0 sccm. With increasing oxygen partial pressure, the Cu metal clusters completely disappear and all the Cu atoms are incorporated substitutionally into the In2O3 lattices at In sites. All the films exhibit intrinsic RT ferromagnetism, and Mott variable range hopping (VRH) transport behavior. The saturation magneti...

Role of pH and Sintering Temperature on the Properties of Tetragonal–Cubic Phases Composed Copper Ferrite Nanoparticles

In the present investigation we have studied the role of varying pH and sintering temperature on the properties of copper ferrite nanoparticles synthesized from metal nitrate solutions by sol–gel auto-combustion technique. The CuFe2O4 samples were synthesized with varying pH values (without maintaining pH, pH 4 and 8). The careful analysis of X-ray diffraction (XRD) result showed that the pH provides boost to develop copper ferrite nanoparticles. The samples without maintaining pH suggested the presence of three different phases. The samples with pH values 4 and 8 showed the tetragonal structure. Crystal structure phase transformation of copper ferrite (pH 8) nanoparticles was studied under different sintering conditions. The prepared samples were characterized by XRD, field emission scanning electron microscopy, FTIR and magnetization. These copper ferrite nanoparticles sintered at different temperatures show combinations of cubic and tetragonal phases. The thermal behavior of as-prepared samples was confirmed by thermo gravimetric/differential thermal analyzer analysis. The morphology of materials was understood by SEM technique. The room temperature magnetic measurement proves strong redistribution of Cu2+ ions. Sintering temperature alerts the saturation magnetization (Ms) to a large extent from 9.26 to 25.15 emu/g.

Effect of Mn doping concentration on structural, vibrational and magnetic properties of NiO nanoparticles

The Ni1−xMnxO (x = 0.00, 0.02, 0.04 and 0.06) nanoparticles were synthesized by chemical precipitation route followed by calcination at 500 °C for 4 h. The prepared samples were characterized by energy dispersive analysis of X-rays (EDAX), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). Rietveld refinement of XRD data confirms the structural phase purity and XRD patterns are well indexed to NaCl like rock salt fcc crystal structure with Fm-3m space group. The particle size of Mn doped samples is found to be less than that of pure NiO sample. However, the particle size increases slightly on increasing the Mn concentration due to surface/grain boundary diffusion. The vibrational properties of the synthesized nanoparticles were investigated by Raman and FT-IR spectroscopy. The results of room temperature magnetization (M-H) and temperature dependent magnetization (M-T) measurements are explained with a core-shell model. The synthesized nanoparticles show weak ferromagnetic and super-paramagnetic like behavior at room temperature.

Structural Properties and Magnetic Interactions in Al3+ and Co2+ Co-Incorporated CdO: Efficient Act of Hydrogenation on Ferromagnetic Order

Nano-powder samples of cadmium oxide doped with Al-Co ions were synthesized by the sol–gel technique using a mixture of complexes of cadmium acetate dihydrate, gadolinium acetate hydrate, and aluminum nitrate nonahydrate. The mass ratios of Al/Cd and Co/Cd in the investigated samples (CdO:Al, CdO:CO, and CdO:Al;Co) were 0.5% and 1%, respectively. X-ray diffraction studies confirmed the formation of a single-phase crystalline structure. Thus, both Al and Co ions were successfully incorporated into the CdO lattice. The present work aims to investigate the possible creation of room-temperature (RT) ferromagnetic properties in host CdO for the field of dilute magnetic semiconductorz (DMS). Annealing in H2 atmosphere under certain conditions was extensively utilized to enhance the Heisenberg interactions between the spins of the incorporated dopant ions which boosted the created FM behavior. Optical measurements revealed the redshift of the bandgap by doping and hydrogenation. RT magnetic measurements disclosed various magnetic properties [diamagnetic, paramagnetic (PM), and FM) at RT depending on the dopant type]. However, the hydrogenation converted all the investigated samples to FM. It was established that the hydrogenation could enhance the saturation magnetisation of CdO:Al:Co nano-powder by ∼ 400 times. Therefore, the system of Al/Co-doped CdO nano-powders, owning these amazingly tunable magnetic properties, can be considered as a potential candidate for many applications such as DMS in addition to its transparent conducting oxide properties.

Investigation of crystal structure and magnetic properties in Zn doped Bi0.84La0.16FeO3 ceramics at morphotropic phase boundary

In this investigation, we have studied the crystal structure and magnetic properties of Zn doped Bi0.84La0.16FeO3 (x = 0.02–0.1) ceramics at the morphotropic phase boundary of rhombohedral and orthorhombic phases. Rietveld refinement of the obtained XRD patterns and Raman spectroscopy confirm the presence of multiphases crystal structure of R3c rhombohedral and Pbam orthorhombic. Room temperature magnetic measurements showed weak ferromagnetic ordering and enhancement in magnetization and coercivity with dominating of orthorhombic phase. The isothermal structural transition from R3c to Pbam is caused for the decrease in magnetization and the increase in coercivity.

A new copper(II) arsenate, Na2Cu3(AsO3OH)4·4H2O containing discrete [Cu3O12]18− units: Synthesis, crystal structure and magnetic properties

Single crystals of the new disodium tricopper(II) tetrakis(hydrogenarsenate(V)) tetrahydrate, Na2Cu3(AsO3OH)4·4H2O were grown under hydrothermal conditions. The compound was characterized by room-temperature single-crystal X-ray diffraction, SEM-EDS analysis, Raman spectroscopy and magnetic susceptibility measurements. Na2Cu3(AsO3OH)4·4H2O represents a new layered structure-type [space group P21/c, a = 8.7089(17), b = 9.7452(19), c = 9.3353(19) Å, β = 92.63(3)°, V = 791.4(3) Å3, Z = 4]. The layers are normal to [100] and are composed of the isolated Cu3O12 units interconnected by AsO3OH coordination tetrahedra. The crystal structure of Na2Cu3(AsO3OH)4·4H2O is related to a group of compounds formed by Cu2+–(XO4)3- layers (X = P5+, As5+) linked by M cations (M = alkali, alkaline earth, Pb2+, or Ag+) and partly by hydrogen bonds, where distinct links and patterns of the Cu3O12 units and XO4 tetrahedra were observed. The magnetic susceptibility and magnetization measurements reveal a canted antiferromagnetic ground state which is in excellent agreement with a layered magnetic structure determined by the copper ions of the Cu3O12 units.

Facile synthesis of quantum sized [formula omitted] nanostructures and their magnetic properties

We examined the quantum sized Co3O4 formation with hexagonal morphology of diameter about 20 nm. The photoluminescence study proved the surface defect-rich Co3O4 nanostructures. The combined synergistic effect of quantum sized hexagonal nanoplates structures and surface defects are favorable for the enhanced magnetic properties in Co3O4 nanostructures. The addition of surfactants and changing of microwave powers led to the paramagnetic behavior. Room temperature magnetic measurements of Ni-doped Co3O4 exhibits weak ferromagnetic nature of Co3O4 nanostructures. With practical, environmental friendly and solvent-free microwave strategy provides a brand new promising route for large-scale preparation of metal oxide for outstanding magnetic performance.

Synthesis, Characterization and Crystal Structures of Mixed-Ligand Complexes of [Cu(bipy)<sub>2</sub>N<sub>3</sub>(ClO<sub>4</sub>)] and [Cu(5,5’-DiMebipy)<sub>2</sub>(N<sub>3</sub>)](ClO<sub>4</sub>)

Two mixed –ligand complexes [Cu(bipy)2N3(ClO4)] and [Cu(5,5’-DiMebipy)2(N3)](ClO4) have been prepared and characterized. The compounds were characterized by elemental analyses, IR and UV-Visible spectroscopy, room temperature magnetic susceptibility measurements, and conductivity measurement, while the solid-state structures have been established by single-crystal X-ray diffraction analyses. [Cu(bipy)2N3(ClO4)]crystallizes in the monoclinic space group P21/c with cell constants a = 16.9027(3) Å, b = 7.59087(9) Å, c = 17.2614(3) Å, β = 111.2808(19)° and Z = 4. [Cu(5,5’-DiMebipy)2(N3)](ClO4) also crystallizes in the monoclinic space group P21/c with the cell constants a = 16.0312(11) Å, b = 7.9889(5) Å, c = 20.7167(18) Å, β = 110.285(8)° and Z = 4. The UV-Vis spectra and X-ray determination indicate that [Cu(bipy)2N3(OClO3)] is distorted octahedral ligand field and non-electrolyte in nature while [Cu(5,5’-DiMebipy)2(N3)](ClO4) is a square pyramidal five coordinate complex and a 1:1 electrolyte. The magnetic moments of the two complexes in the range 1.78–1.83 B.M. reveal a single unpaired electron with a slight orbital contribution.

Synthesis, characterization, antimicrobial activity and DFT studies of 2-(pyrimidin-2-ylamino)naphthalene-1,4-dione and its Mn(II), Co(II), Ni(II) and Zn(II) complexes

A pyrimidine-based ligand, 2-(pyrimidin-2-ylamino)naphthalene-1,4-dione (L), has been synthesized by the reaction of 2-aminopyrimidine with 2-hydroxy-1,4-napthoquinone. Reaction of the ligand with Ni(II), Co(II), Mn(II) and Zn(II) acetate gave the corresponding metal complexes which were characterized by spectroscopic techniques, (infrared, electronic), elemental analysis, room-temperature magnetometry, conductance measurements and thermogravimetry-differential scanning calorimetry (TG-DSC) analyses. The room-temperature magnetic data and electronic spectral measurements of the complexes gave evidence of 4-coordinate square planar/tetrahedral geometry. The thermal analyses values obtained indicated the monohydrate complexes. The antimicrobial screening of the compounds showed mild to very good results. The Mn(II) complex showed the best result within in the range of 11.5–29 mm. The electronic, structural and spectroscopic properties of the complexes were further discussed using density functional theory. Molecular docking studies showed significant binding affinity with the drug targets and the metal complexes have potentials to be used as drugs.

Ultra-soft magnetic Co-Fe-B-Si-Nb amorphous alloys for high frequency power applications

With the continuous shrinkage of the footprint of inductors and transformers in modern power supplies, higher flux, while still low-loss metallic replacements of traditional ferrite materials are becoming an intriguing alternative. One candidate replacement strategy is based on amorphous CoFeBSi soft-magnetic alloys, in their metallic glass form. Here the structural and magnetic properties of two different families of CoFeBSi-based soft magnetic alloys, prepared by arc-melting and subsequent melt spinning (rapid quenching) are presented, targeting potential applications at effective frequencies of 100 kHz and beyond. The nominal alloy compositions are Co67Fe4B11Si16Mo2 representing commercial Vitrovac and Co72-xFexB28-y (where B includes non-magnetic elements such as Boron, Silicon etc. x varies between 4 and 5 % and y is varied from 0 to 2 %) denoted Alloy #1 and prepared as a possible higher performance alternative, i.e. lower power loss and lower coercivity, to commercial Vitrovac. Room temperature magnetization measurements of the arc-melted alloys reveal that compared to Vitrovac, Alloy #1 already presents a ten-fold decrease in coercivity, with Hc ∼ 1.4 Am-1 and highest figure of merit of (Ms/Hc > 96). Upon melt-spinning the alloys into thin (< 30 μm) ribbons, the alloys are essentially amorphous when analyzed by XRD. Magnetization measurements of the melt-spun ribbons demonstrate that Alloy #1 possesses a coercivity of just 2 Am-1, which represents a significant improvement compared to melt-spun ribbons of Vitrovac (17 Am-1). A set of prototype transformers of approximately 10 turns of Alloy #1 ribbon exhibits systematically Hc < 10 Am-1 at 100 kHz, without a noticeable decrease in coupled flux and saturation.

Magnetic and Structural Studies of Complexes of Isonitrosopropiophenone Thiocarbonohydrzone Benzaldehydes with Ni (II), Pd (II) and Pt(II)

A novel Ni(II), Pd(II) and Pt(II) complexes of Isonitrosopropiophenone thiocarbonohydrzone benzaldehydes derived from N”-[(1Z, 2E)-(hydroxyimino)-1-phenylpropylidene]thiocarbonohydrazide (HTIPP)and substituted benzaldehydes, have been synthesized and studied. Six new ligands are reported herein using two electron withdrawing (−Cl, -NO2) and two electron donating (−OH,-OCH3) substituents benzaldehyde and HTIPP. Their structures have been discussed on the basis of spectral, magnetic and powdered X-ray crystallography studies. The dimeric nature of the complexes supported by molecular weight determinations by Rast method. The result so obtained suggest binuclear distorted octahedral geometry for Ni(II) complexes, while mononuclear square planar geometry for Pd(II) and Pt(II) complexes. The room temperature magnetic susceptibility measurements reveals that antiferromagnetic interactions exists between the high spin Ni(II) ions within the dinuclear unit. The powdered X-ray crystallography study reveals orthorhombic crystal system for Ni(II) complexes.

Structural, electrical and magnetic study of multiferroic Bi1 − xNdxFeO3

The multiferroic Bi1 − xNdxFeO3 polycrystalline samples were prepared by the conventional solid-state reaction method and were observed to possess the desired phase, i.e., the single-phase. X-ray diffraction of the prepared samples was performed to analyse the crystal structure and to determine the lattice parameters. IR technique was used to recognise and understand the bonding nature of the prepared samples. The ferroelectric nature was identified by taking the P–E loops at various applied voltages, showing improvement in values of remnant polarisation and spontaneous polarisation. The J–E characteristics reveal the resistivity of all the prepared samples and found to have been enhanced largely in Nd-doped samples. The room temperature magnetic hysteresis measurements showed growth in the magnetisation due to the change in structure and spin cycloidal partial destruction produced due to Nd doping in BFO ceramics.

Enhancing ferromagnetic properties in bismuth ferrites with non-magnetic Y and Sc co-doping

Polycrystalline \({\text{Bi}}_{{1 - x}} {\text{Y}}_{x} {\text{Fe}}_{{0.97}} {\text{Sc}}_{{0.05}} {\text{O}}_{3}\) \((\hbox {x}=0\), 0.06, 0.12; \(\hbox {y}=0.05)\) were prepared by solid-state method by high energy ball milling technique. X-ray diffraction studies confirm polycrystalline nature of the samples with rhombohedral perovskite structure (R3c: Space group). DTA confirms the successfully phase formation in all samples. Room temperature Raman measurements reveal that lattice distortions occur by insertion of Y and Sc at A and B-site of BFO respectively, which may improve the magnetic properties. UV–Visible analysis confirms small band gap tuning in doped BFO resulting in due to the change in Fe–O (bond length) and Fe–O–Fe (bond angle). Room temperature magnetic measurements reveal an improved magnetic properties with saturated magnetization \((M_s = 4.503\hbox { emu/gm})\), remanent magnetization \((M_r = 1.514\hbox { emu/gm})\), coercive field \((H_c = 259.33\hbox { Oe})\) for 12% doping concentration. Co-doping of Y and Sc leads to modification in the spiral modulated spin structure resulting in soft ferromagnetic behavior in contrast to G-type anti-ferromagnetic nature of the parent compound.

Structural, Microstructural, Magnetic, and Ferroelectric Properties of Ba 2 + -Doped BiFeO3 Nanocrystalline Multifferroic Material

Multiferroic barium-substituted nanocrystalline samples having the general formula Bi1−x Ba x FeO3 (where x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared by cost-effective sol–gel method using metal nitrates as oxidants. The prepared samples were annealed at 650 ∘C for 4 h using a muffle furnace. The influence of Ba2+ doping on the structural, microstructural, magnetic, and ferroelectric properties of bismuth ferrite (BFO) was studied systematically by standard techniques. All the samples were characterized by X-ray diffraction (XRD) technique, and the average crystallite size was calculated using Scherrer’s formula. The surface morphology of the prepared nanocrystalline samples was studied using field emission scanning electron microscopy (FE-SEM) technique. FTIR spectra were obtained to confirm the formation of the perovskite structures. The elemental compositional details obtained were confirmed by energy dispersive spectrum (EDS) analysis. Room temperature magnetic measurements were carried out up to a field of 15 kOe, and the parent sample (BFO) shows weak ferromagnetism. Further on, Ba2+ substitution in BFO shows an increase in magnetization. P–E loops were obtained to study the ferroelectric properties of all the samples. Obtained enhancement in magnetic and ferroelectric properties at room temperature is of great interest within the research community due to its wide range of applications in memory storage, spintronics, sensors, and multi-functional devices.

Structural and magnetic properties of cobalt ferrite nanoparticles synthesized by co-precipitation at increasing temperatures

This study reports on the synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles (NPs) synthesized by chemical co-precipitation in alkaline medium at increasing temperatures in the range of 27 °C to 100 °C. High-quality samples in the size range of 5 to 10 nm were produced using very low stirring speed (250 rpm) and moderate alkaline aqueous solution concentration (4.8 mol/L). Three samples were synthesized and characterized by x–ray diffraction (XRD) and room-temperature (RT) magnetization measurements. All samples present superparamagnetic (SPM) behavior at RT and Rietveld refinements confirm the inverse cubic spinel structure (space group Fd-3m (227)) with minor detectable impurity phase. As the synthesis temperature increases, structural parameters such as lattice constant and grain size change monotonically from 8.385 to 8.383 Å and from 5.8 to 7.4 nm, respectively. Likewise, as the synthesis temperature increases the NPs’ magnetic moment and saturation magnetization increases monotonically from 2.6 ×103 to 16×103 μB and from 37 to 66 emu/g, respectively. The RT magnetization (M) versus applied field (H) curves were analyzed by the first-order Langevin function averaged out by a lognormal distribution function of magnetic moments. The excellent curve-fitting of the M versus H data is credited to a reduced particle-particle interaction due to both the SPM behavior and the existence of a surface amorphous shell layer (dead layer), the latter reducing systematically as the synthesis temperature increases.

Growth and magnetic properties of spin coated Co0.6Zn0.4Mn0.3Fe1.7O4 ultrathin films on silicon (100), (110) and (111) substrates

This paper reports growth of Co0.6Zn0.4Mn0.3Fe1.7O4 (CZFMO) ultrathin films (thickness: 23–30 nm) by spin coating technique on silicon (100), (110) and (111) substrates. The deposited films were annealed at 700 °C for 1 h in the oxygen environment. All the films were found to be polycrystalline in nature. The CZFMO films were found to have minimal residual stress (13–50 MPa), which could be an encouraging feature for novel microwave miniaturized device applications. Room temperature magnetic measurements demonstrated completely saturated hysteresis loop with the highest squareness ratio (M R /M S ) ~ 60% for the film grown on Si (110) substrate. On the other hand CZFMO films on Si (100) and Si (111) substrates showed unsaturated hysteresis loops with M R /M S ~ 10 and 5%, respectively. The reason for the better magnetic properties of the ultrathin CZFMO film on Si (110) substrate seems to be its better crystalline quality and larger grain size compared to those of other films.

Synthesis and phosphatase activity of a Cobalt(II) phenanthroline complex

A mononuclear cobalt(II) complex, [ $$\hbox {Co}\hbox {(phen)}_{2}\hbox {Cl}_{2}$$ ], (phen = 1,10-phenanthroline) has been synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray structural study. X-ray crystal structural analysis revealed that the cobalt(II) complex crystallizes in a monoclinic system with C2 / c space group and exists in cis-configuration in its crystalline state. Room temperature magnetic measurement accounts for 3e paramagnetism and indicates high spin cobalt(II) in the solid state. The cobalt(II) complex has been evaluated as a functional model for phosphatase enzyme by using 4-nitrophenylphosphate (PNPP) as a standard substrate in aqueous DMF medium. This mononuclear cobalt(II) complex exhibits good hydrolytic phosphoester cleavage efficiency with $$k_{\mathrm{cat}}$$ value of $$3.78\times 10^{2}\hbox {h}^{-1}$$ . SYNOPSIS The cobalt(II) complex of phenanthroline exhibits good catalytic activity towards 4-nitrophenylphosphate (PNPP) as a standard substrate in aqueous DMF medium with $$k_{\mathrm{cat}}$$ value of $$3.78\times 10^{2} \hbox { h}^{-1}$$ . .