Ferromagnetics

• Straightforward synthesis for 0-3 Sr 0.5 Ba 0.5 Nb 2 O 6-CoFe 2 O 4 composites. • Monitoring the phase evolution during sintering to ceramics bodies. • Determination of Curie temperature. • Impedance spectroscopy up to 200 • C and 10 MHz. • Investigations of the magnetoelectric coefficient in dependence on magnetic DC field, frequency, and temperature.

MANYETİZMA
Manyetizmanın Tarihi
Manyetizmanın Tanımı
Mıknatıslanmanın Tanımı
Doyma Mıknatıslanması
Manyetik Bölgeler
MANYETİZMA ÇEŞİTLERİ
Paramanyetizma
Diyamanyetizma
Ferromanyetizma
Antiferromanyetizma
Ferrimanyetizma
MANYETİK ALINGANLIK
Manyetik Alınganlığın Tanımı
Manyetik Alınganlık Ölçüm Yöntemi
Manyetik Alınganlık Ölçüm Sistemi

RESUMEN En este artículo se lleva a cabo la oxidación rápida y controlada del sulfato de hierro hidratado, denominado tradicionalmente caparrosa. El Fe +2 de la caparrosa se oxidará parcialmente formando como compuesto principal Fe 3 O 4 junto al compuesto completamente oxidado Fe 2 O 3 que aparecerá en cantidades menores. El resultado es un fluido ferromagnético que sólo exhibe su magnetismo en presencia de un campo magnético intenso, como el de un imán de neodimio.
ABSTRACT In this paper I show the quick and controlled oxidation of iron (II) sulfate, traditionally named copperas. The cation Fe +2 of the sulfate oxidizes partially into Fe +3 rending Fe 3 O 4 as main product besides Fe 2 O 3 the compound of iron that is completely oxidized and appears in a lesser proportion. The result is a ferromagnetic fluid that only shows its magnetism inside a strong magnetic field, like that of a neodymium magnet.

Density functional theory calculations were employed to model the electronic structure and the magnetic interactions in copper doped anatase and rutile titanium dioxide in order to shed light on the potential of these systems as magnetic oxides using different density functional schemes. In both polymorphs, copper dopant was found to be most stable in substitutional lattice positions. Ferromagnetism is predicted to be stable well above room temperature with long range interactions prevailing in the anatase phase while the rutile phase exhibits only short range superexchange interaction among nearest-neighbour Cu ions. Additionally, energetic evaluation of dopants in scattered and compact configurations reveals a dopant clustering tendency in anatase TiO2.

We present a method for the fabrication of PVPA/ BaFe 12 O 19 nanocomposite by in-situ polymerization of vinyl phosphonic acid, VPA in the presence of synthesized BaFe 12 O 19 NPs. Nanoparticles and the nanocomposite were analyzed by XRD, FTIR, TGA, SEM, TEM, VSM, and conductivity techniques for structural and physicochemical characteristics. Nanoparticles, identified as BaFe 12 O 19 from XRD analysis, were successfully coated with PVPA and the linkage was assessed to be via P-O bonds. Electron microscopy analysis revealed aggregation of BaFe 12 O 19 particles and dominantly platelet morphology upon composite formation. TGA analysis revealed the composition of the nanocomposite as 65% BaFe 12 O 19 and 35% polymer. Magnetic evaluation revealed that adsorption of PVPA anions during the preparation of the nanocomposite strongly influenced the magnetic properties resulting in much lower saturation magnetization values. DC conductivity measurements were used to calculate activation energy of PVPA/BaFe 12 O 19 nanocomposite and it was obtained as 0.37 eV.

A controlled technique for embedding ferromagnetic nanoparticles in a diamagnetic PVC matrix with uniform dispersion and a wide particle concentration range is described here. The resulting material is a magnetopolymeric nanocomposite with combined magnetic and polymeric properties. The tailoring of its magnetic response can be tuned through the control of nearly spherical Co80Ni20 nanoparticles around 65 nm average diameter, prepared by the polyol method, and their concentration in the matrix (in the range 0.5–50 wt%). This material is nearly ready for practical applications.

The differences between amorphous and glassy state are discussed and the methods of their preparation reviewed. The role of crystallization during fast cooling is analyzed and nucleation-growth process is shown in two attitude models, which characterization are depicted on DTA curves. Specificity of non- and nano-crystalline metallic glasses is revealed.

Nanocomposites of linear chain of ferroelectric-ferromagnetic crystal structure is considered. It is analyzed theoretically in the motion equation method on the pursuit of magnonic excitations,lattice vibration excitations and their interactions leading to a new collective mode of excitations,the electormagnons. In this particular work, it is observed that the magnetizations and polarizations are tunable in a given temperature ranges for some specific values of the coupling order parameter.

Pure BiFeO3 (BFO) and La-modified BiFeO3 (Bi1−xLaxFeO3 with x = 0.2 and 0.4) ceramic powders were synthesized at relatively low temperature by ferrioxalate precursor method. Pure compositions did not yield phase pure powders and contain secondary phases. At the same time, La-modification at different concentration levels inBFOpromoted the formation of perovskite phase with the elimination of secondary phases and phase pure ceramic powders were obtained for the composition Bi1−xLaxFeO3 with x = 0.4. Further, the effect of lanthanum substitution on the morphology, electrical and magnetic properties was also investigated.

Magnetite nanoparticles doped with Na + ions are prepared by co-precipitation method and characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Vibrating sample magnetometer (VSM), Dynamic light scattering (DLS), Differential scanning calorimetry (DSC) and Fourier transform Infrared spectroscopy (FTIR). The -Fe 2 O 3 to -Fe 2 O 3 phase transition temperature is found to increase with Na + concentration and the saturation magnetization is found to decrease from 65 to 48 emu/g with 500 ppm Na + . With 500 ppm of Na + , the samples retained the saturation magnetization of 46 emu/g, even after air annealing at 600 C. The phase analysis done using Rietveld shows that the percentage of hematite ( -Fe 2 O 3 ) formed after air annealing at 600 C is found to decrease with increase in Na + concentration. The differential scanning calorimetric studies also confirm the enhanced temperature stability upon Na doping. The zeta potential of undoped and Na + doped magnetite particles are found to be −28 and −37 mV respectively. The enhanced zeta potential of doped particles unambiguously confirms that Na + ions are diffused into the crystals, which enhances the electrostatic stabilization of suspended particles.

Nanocrystalline Fe77Zr7N16 films are prepared by oblique-angle magnetron sputtering. The effect of the ion beam angle and subsequent annealing on the phase and structural states, the coercive force, the saturation magnetization, the remanent magnetization, and the induced in-plane magnetic anisotropy field has been studied. The possibility of natural ferromagnetic resonance in these films at gigahertz frequencies is estimated.

Bulk crystals and thin films of PbTi12xFexO32d (PTFO) are multiferroic, exhibiting ferroelectricity and ferromagnetism at room temperature. Here we report that the Ruddlesden-Popper phase Pbn11(Ti12xFex)nO3n112d forms spontaneously during pulsed laser deposition of PTFO on LaAlO3 substrates. High-resolution transmission electron microscopy, x-ray diffraction and x-ray photoemission spectroscopy were utilised to perform a structural and compositional analysis, demonstrating that n^8 and x^0:5. The complex dielectric function of the films was determined from far-infrared to ultraviolet energies using a combination of terahertz time-domain spectroscopy, Fourier transform spectroscopy, and spectroscopic ellipsometry. The simultaneous Raman and infrared activity of phonon modes and the observation of second harmonic generation establishes a non-centrosymmetric point group for Pbn11(Ti0.5Fe0.5)nO3n112d, a prerequisite for (but not proof of) ferroelectricity. No evidence of macroscopic ferromagnetism was found in SQUID magnetometry. The ultrafast optical response exhibited coherent magnon oscillations compatible with local magnetic order, and additionally was used to study photocarrier cooling on picosecond timescales. An optical gap smaller than that of BiFeO3 and long photocarrier lifetimes may make this system interesting as a ferroelectric photovoltaic.

The synthesis of nano-crystalline CuFe2O4 powders by a combustion-like process is described herein. Phase formation and evolution of the crystallite size during the decomposition process of a (CuFe2)—precursor gel were monitored up to 1000 °C. Phase-pure nano-sized CuFe2O4 powders were obtained after reaction at 750 °C for 2 h resulting in a crystallite size of 36 nm, which increases to 96 nm after calcining at 1000 °C. The activation energy of the crystallite growth process was calculated as 389 kJ mol−1. The tetragonal⇄⇄cubic phase transition occurs between 402 and 419 °C and the enthalpy change (ΔH) was found to range between 1020 and 1229 J mol−1 depending on the calcination temperature. The optical band gap depends on the calcination temperature and was found between 2.03 and 1.89 eV. The shrinkage and sintering behaviour of compacted powders were examined. Dense ceramic bodies can be obtained either after conventional sintering at 950 °C or after a two-step sintering process at 800 °C. Magnetic measurements of both powders and corresponding ceramic bodies show that the saturation magnetization rises with increasing calcination-/sintering temperature up to 49.1 emu g−1 (2.1 µB fu−1), whereas the coercivity and remanence values decrease.

Polyol methods to synthesize nanoparticles and their arrays are firstly described.Magnetic nanoparticles selfassemble
under particular conditions into spherical superstructures, like CoNi nanoparticles, or planar structures with hexagonal ordering, like FePt nanoparticles.Particles and their arrays are structurally analysed by techniques like TEM, X-ray, etc. Magnetic characterization is firstly performed by VSM magnetomer as a function of the nanoparticles size paying particular attention to the transition from multidomain to single-domain structures.Later on, magnetic exchange coupling effects are discussed including the temperature dependence of magnetic parameters as coercive and exchange bias fields, as well as the influence of field or zero-field cooling processes. Finally, magnetic polymers consisting of magnetic nanoparticles embedded into PVC polymeric matrix are prepared and magnetically analysed.

Nanocrystalline Fe77Zr7N16 films are prepared by oblique-angle magnetron sputtering. The effect of the ion beam angle and subsequent annealing on the phase and structural states, the coercive force, the saturation magnetization, the remanent magnetization, and the induced in-plane magnetic anisotropy field has been studied. The possibility of natural ferromagnetic resonance in these films at gigahertz frequencies is estimated.

BaTiO3-MgFe2O4 composites (30 wt.% MgFe2O4) with a small addition of BaGeO3 as a sintering additive were synthesized by a one-pot Pechini-like sol-gel process. Nano-crystalline composite powders with a crystallite size of about 10 nm were obtained after reaction at 700 °C for 1 h. Magnetic investigations suggest that the nano-powder is in its superparamagnetic state at room temperature. The addition of BaGeO3 leads to an improved sintering behaviour. DTA measurements reveal the formation of a liquid phase at 1164(3) °C. Dense ceramic bodies (relative density > 90 %) were obtained after sintering for 1 h at 1150 °C. SEM investigations prove a 0-3 connectivity and show that the addition of BaGeO3 promotes the grain growth leading to particles up to 4 µm. In contrast, fine-grained composite ceramics with smaller particles up to 230 nm were obtained after a two-step sintering process. Magnetic measurements indicate a ferrimagnetic behaviour with coercivity values up to 70 Oe depending on the sintering procedure. Furthermore, addition of BaGeO3 results in an increase of the relative permittivity, whereas the dissipation factor slightly decreases

Monodispersed spherical Co80Ni20 nanoparticles with diameters between 10 and 540 nm have been prepared by boiling liquid reduction of cobalt and nickel salts through a heterogeneous nucleation process (polyol process). All samples exhibit a core/shell structure with a ferromagnetic core surrounded by a surface layer consisting of antiferromagnetic oxides and organic matter. The ferromagnetic/antiferromagnetic interface, which arises from the core/shell structure, induces an exchange anisotropy at low temperature when the samples are subjected to a field cooling process or to a zero field cooling process starting from a remanent state. The shift of the hysteresis loops (exchange bias) and the increment of the coercive field are consequences of the presence of this magnetic anisotropy. The effect of the particle size, the temperature and the cooling process on the magnetic behaviour of the samples has been analysed.

We report on studies of magneto-transport properties and structure (by neutron and X-ray diffraction techniques) at 5-300K in glass coated Co29Ni25Mn1Cu45 microwires prepared by the Taylor-Ulitovsky technique. Annealing of the sample (973 K during 1 hour) results in an increasing of room temperature coercivity (Hc45) from 65 Oe up to 800 Oe. Considerable magneto-resistance, MR, is found in both in asprepared and annealed microwires increasing up to about
4% in the annealed samples. Magnetic field dependence of MR in as-prepared and annealed samples is quite different. Roughly monotonic decay is observed in as-prepared microwires. Annealed sample
exhibits a maximum and considerable hysteresis on magnetic
field dependence of MR. Neutron diffraction allows to distinguish two peaks in the as-prepared sample and 3 peaks in annealed samples. Observed changes in temperature dependence of magnetic properties
and of MR are correlated to the structure changes with temperature.

Pure BiFeO 3 (BFO) and La-modified BiFeO 3 (Bi 1−x La x FeO 3 with x = 0.2 and 0.4) ceramic powders were synthesized at relatively low temperature by ferrioxalate precursor method. Pure compositions did not yield phase pure powders and contain secondary phases. At the same time, La-modification at different concentration levels in BFO promoted the formation of perovskite phase with the elimination of secondary phases and phase pure ceramic powders were obtained for the composition Bi 1−x La x FeO 3 with x = 0.4. Further, the effect of lanthanum substitution on the morphology, electrical and magnetic properties was also investigated.

Cadmium sulfide (CdS) is one of the most promising materials for solar cells and of great interest for their practical applications in electronics and photonics. Yellow colored CdS nanoparticles were synthesized by wet chemical route at room temperature using 2-mercaptoethanol was used as the capping agent. The crystallographic and optical properties of CdS nanoparticles have been characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and UV-Vis-NIR absorption spectroscopy. XRD analysis showed that CdS nanoparticles have cubic Zinc blend crystal structure. The average crystalline size determined by using Debye Scherrer's formula was of the order of 2.34 nm. The lattice constant and other crystallographic parameter were obtained using XRD data. The functional groups and chemical interaction were determined by FTIR spectra. From FTIR spectra, it is investigated that absorption bands show the presence of resonance interaction between vibrational modes of oxide ions in the crystal. UV-Visible absorption spectrum of CdS nanoparticles showed that absorption edge  max = 501 nm and corresponding band gap energy is found to be E g = 2.46 eV. In the present work, we have reported the crystallographic and optical properties of CdS nanoparticles synthesized by a colloidal wet chemical route.

Enhanced ferromagnetic and visible light active titanium dioxide (TiO2) photocatalyst was synthesised by depositing a hard ferromagnet strontium ferrite (SrFe12O19) onto TiO2 via an effortless hydrothermal and poly-condensation method. The catalysts were characterised by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), BET surface analysis, vibrating sample magnetometer (VSM), X-ray photon spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and UV-visible light spectroscopy analysis. The prepared nanocomposite photocatalyst exhibited physically a powerful ferromagnetic property with significant stability against the loss of its magnetic property (coercivity ≈2200 G). The catalyst can be fluidised and recovered by an external magnetic field enhancing separation and mixing efficiency. Furthermore, it resulted in a reduced band gap (≈2.3 eV) which resulted in enhanced visible light absorption compared with unsupported TiO2. The photocatalytic activity was investigated by degrading a recalcitrant phenolic compound, viz., 2, 4-dichlorophenol (2,4-DCP) as model pollutant under different illuminance of daylight. Complete degradation of 2,4-DCP (50 mg/L initial concentration in 0.25 L) was achieved in 120 min (supported photocatalyst) and 180 min (unsupported TiO2) under higher illuminance of sunlight. Likewise under diffused sunlight, 100% degradation of 2,4-DCP was achieved in 240 min for the supported TiO2, while ≥90% degradation could be achieved in 300 min for the unsupported TiO2. The supported nanocomposite was recycled under a permanent magnetic field with a mass recovery of 98% and reused. © 2013 Copyright Taylor and Francis Group, LLC.

http://www.tandfonline.com/doi/abs/10.1080/17458080.2012.675087

A systematic study on the magnetic and electrical transport properties of single-phase wurtzite Zn 1−x Cu x O is performed. Efros variable range hopping dominates the conduction, which is accompanied by a ferromagnetic order up to 700 K for x Ͼ 1%. Both the first-principles calculations and Cu/Al co-doping experiments suggest that the spontaneous spin polarization originates from the p-d exchange interaction between O 2p and Cu 3d orbitals. Furthermore, our results are consistent with the scenario that the intrinsic ferromagnetism is established through indirect interactions between bound magnetic polarons mediated by magnetic impurities.

Abstract A single-phase sample of the Aurivillius compound Pb0.4Bi2.1La0.5Nb1.7Mn0.3O9 was prepared by a molten salt method using K2SO4/Na2SO4 as the flux. The crystal structure, morphology, ferroelectric, and magnetic properties were investigated. Neutron powder diffraction data confirmed a non-centrosymmetric orthorhombic crystal structure with space group A21am and Pb/Bi disorder in the bismuth oxide blocks, Bi/Pb/La disorder on the perovskite A-site, and Nb/Mn disorder on the perovskite B-site. The morphology of the sample showed anisotropic plate-like grains as probed by scanning electron microscopy. The dielectric constant exhibits a transition peak between 600 K and 640 K that depends on frequency, indicating relaxor ferroelectric behavior. Electrical polarization versus applied field loops are unsaturated, with a remnant polarization of 0.43 μC/cm2 at 40 Hz under the maximum electrical field applied of 160 kV/cm. The ferroelectricity originates from the displacement of oxygen atoms in the BO6 octahedra, resulting in a polar structural distortion. Magnetic susceptibility measurements showed the presence of mixed Mn3+ and Mn4+, resulting in short-range ferromagnetic order via double exchange interactions below 33 K. The remnant magnetization (Mr) is 0.01 emu/g at 5 K. This mixed valence of Mn cations is mainly responsible for the high electrical conductivity. Thus, Pb0.4Bi2.1La0.5Nb1.7Mn0.3O9 exhibits coexisting ferroelectric and ferromagnetic properties.

A novel investigation on a relationship between temperature-influential self-assembly (70–300 • C) of 4-pentynoic acid functionalized Fe3O4-Fe 2O3 nanoparticles (NPs) on SiO2/n-Si with electrical properties was reported with the interests for metal-oxide-semiconductor applications. X-ray diffractometer (XRD) analysis conveyed that 8 ± 1 nm of the NPs were assembled. Increasing heating temperature induced growth of native oxide (SiO2). Raman analysis confirmed the coexistence of Fe3O4-Fe2O3. Attenuated Total Reflectance Infrared (ATR-IR) spectra showed that self-assembly occurred via Si-O-C linkages. While Si-O-C linkages were broken down at elevated temperatures, formations of Si-OH defects were amplified; a consequence of physisorbed surfactants disintegration. Atomic force microscopy (AFM) showed that sample with more physisorbed surfactants exhibited the highest root-mean-square (RMS) roughness (18.12 ± 7.13 nm) whereas sample with lesser physisorbed surfactants displayed otherwise (12.99 ± 4.39 nm RMS roughness). Field Emission Scanning Electron Microscope (FE-SEM) analysis showed non-uniform aggregation of the NPs, deposited as film (12.6 m thickness). The increased saturation magnetization (71.527 A m 2 /kg) and coercivity (929.942 A/m) acquired by vibrating sample magnetometer (VSM) of the sample heated at 300 • C verified the surfactants' disintegration. Leakage current density-electric field (J-E) characteristics showed that sample heated at 150 • C with the most aggregated NPs as well as the most developed Si O C linkages demonstrated the highest breakdown field and barrier height at 2.58 × 10 −3 MV/cm and 0.38 eV respectively. Whereas sample heated at 300 • C with the least Si O C linkages as well as lesser aggregated NPs showed the lowest breakdown field and barrier height at 1.08 × 10 −3 MV/cm and 0.19 eV respectively. This study opens up better under-standings on how formation and breaking down of covalent linkages as well as accumulation of defects, particularly prior temperature influential self-assembly at the interfaces, affected electrical breakdown field and barrier height. Hence, possible future development of self-assembly silicon-based metal-oxide-semiconductor (MOS) structure particularly in the presence of SiO2 can be deliberated.

One of the top efficient nonlinear optical crystals, ZnGeP 2 , is being used at present in parametric oscillators and second-harmonic and combination frequency generators for the mid-IR spectral range. Until recently, this crystal has not been thought of as a magnetic medium, and strong magnetic phenomena were assumed to not occur in it. The recent discovery of a new magnetically ordered state in ZnGeP 2 and CdGeP 2 single crystals and films doped with Mn shows that this material exhibits ferromagnetic phenomena and, if deposited on a host nonlinear single crystal, can be considered a promising magneto-optical medium. We report on nonlinear parameters of undoped and doped ZnGeP 2 and current data on magnetic phenomena in (Zn,Mn)GeP 2 and (Cd,Mn)GeP 2 ferromagnetic layers and doped ZnGeP 2 : Mn single crystals. Stabilizing a heterosystem constituted by ferromagnetic layers on a nonmagnetic nonlinear crystal extends the scope of possible designs of magneto-optical, spin-dependent, and magnetically controllable nonlinear optical devices. crystals with the best-achieved nonlinear optical parameters and the properties of Mn-doped ZnGeP 2 and CdGeP 2 crystals.

We report on a comprehensive optical, transport and thermodynamic study of the Zintl compound Yb14MnSb11, demonstrating that it is the first ferromagnetic Kondo lattice compound in the underscreened limit. We propose a scenerio whereby the combination of Kondo and Jahn-Teller effects provides a consistent explanation of both transport and optical data.

Ferromagnetic resonance FMR and microwave magnetoabsorption can be expected to be powerful tools for characterization of magnetic nanoparticles. In the present work, we have studied the FMR and magnetic field dependence of nonresonant microwave losses in CoNi nanoparticles of about 45, 100, and 200 nm caliper sizes prepared by the polyol technique. Contrary to our expectation, FMR lines, although wide, show that the particles are not truly spherical. Subsequent scanning and transmission electron microscopy investigations have confirmed this finding. Further, as before, all the powders are found to have large zero field absorption which reduces on application of a direct current 􏰎dc􏰍 field parallel to the microwave magnetic field but is relatively insensitive to a dc field if the powder is located in the microwave electric field, hence defining a magnetoimpedance for the system.

Nanostructure-related magnetic properties are investigated systematically for various mesoporous cobalt oxide (Co3O4) and cobalt ferrite (CoFe2O4) spinel phases. Synthesis of the materials by nanocasting offers the opportunity to obtain materials which are different from each other with respect to both specific surface area and crystallite size. As a result, the respective contributions of two types of interfaces, namely, “solid–gas” and “solid–solid” interfaces, to the magnetic ordering can be distinguished. Structural characterization of the porous materials by X-ray diffraction, N2 physisorption, and electron microscopy as well as investigation of the magnetic behavior (field-dependent magnetization and temperature-dependent susceptibility) are presented.

One of the top efficient nonlinear optical crystals, ZnGeP 2 , is being used at present in parametric oscillators and second-harmonic and combination frequency generators for the mid-IR spectral range. Until recently, this crystal has not been thought of as a magnetic medium, and strong magnetic phenomena were assumed to not occur in it. The recent discovery of a new magnetically ordered state in ZnGeP 2 and CdGeP 2 single crystals and films doped with Mn shows that this material exhibits ferromagnetic phenomena and, if deposited on a host nonlinear single crystal, can be considered a promising magneto-optical medium. We report on nonlinear parameters of undoped and doped ZnGeP 2 and current data on magnetic phenomena in (Zn,Mn)GeP 2 and (Cd,Mn)GeP 2 ferromagnetic layers and doped ZnGeP 2 : Mn single crystals. Stabilizing a heterosystem constituted by ferromagnetic layers on a nonmagnetic nonlinear crystal extends the scope of possible designs of magneto-optical, spin-dependent, and magnetically controllable nonlinear optical devices. crystals with the best-achieved nonlinear optical parameters and the properties of Mn-doped ZnGeP 2 and CdGeP 2 crystals.

The magnetic structure of Fe(100-x)Zr(x) films (x = 0, 0.6, 1.8, 2.9, and 4.1 +/- 0.1 at%), which is characterized by the existence of stochastic domains determined by correlation magnetometry method, is discussed in terms of the random anisotropy model. It is found that two modes of the magnetic anisotropy field of stochastic domains are formed, which differ in the exchange stiffness magnitude and determine the existence of two modes of the coercive field found in the magnetic hysteresis loops.

The existence and feasibility of the multicaloric, polycrystalline material 0.8Pb(Fe 1/2 Nb 1/2)O 3-0.2Pb(Mg 1/2 W 1/2) O 3 , exhibiting magnetocaloric and electrocaloric properties, are demonstrated. Both the electrocaloric and magnetocaloric effects are observed over a broad temperature range below room temperature. The maximum magnetocaloric temperature change of ~0.26 K is obtained with a magnetic-field amplitude of 70 kOe at a temperature of 5 K, while the maximum electrocaloric temperature change of ~0.25 K is obtained with an electric-field amplitude of 60 kV/cm at a temperature of 180 K. The material allows a multicaloric cooling mode or a separate caloric-modes operation depending on the origin of the external field and the temperature at which the field is applied. The search for caloric materials to be applied in solid-state refrigeration has recently become one of the most active fields in condensed-matter science 1-6. The caloric effect is related to a change of the material's entropy under the sudden application of an external field: magnetic, electric, or mechanical 1,2,7,8. Depending on the origin of the entropy change, the caloric effects can be classified as magnetocaloric (MC), electrocaloric (EC) and mechanocaloric (mC), the last of which includes the elastocaloric and barrocaloric effects 1. For all three individual effects prototype cooling devices have already been proposed 7,9-11. Lately, materials exhibiting multicaloric properties have become the "holy grail" of developments in new, solid-state cooling technologies. Until recently, the coexistence of the MC and EC effects had only been proposed theoretically 12-16. According to a recent review of caloric materials 1 this coexistence has not been experimentally confirmed, as it is difficult to find a multiferroic material that exhibits both ferromagnetism and ferroelectricity. More recently, a study appeared reporting the multicaloric Y 2 CoMnO 6 17

Nanostructure-related magnetic properties are investigated systematically for various mesoporous cobalt oxide (Co3O4) and cobalt ferrite (CoFe2O4) spinel phases. Synthesis of thematerials by nanocasting offers the opportunity to obtain materials which are different from each other with respect to both specific surface area and crystallite size. As a result, the respective contributions of two types of interfaces, namely, “solid–gas” and “solid–solid” interfaces, to the magnetic ordering can be distinguished. Structural characterization of the porous materials by X-ray diffraction, N2 physisorption, and electron microscopy as well as investigation of the magnetic behavior (field-dependent magnetization and temperaturedependentsusceptibility) are presented.

Nanocomposites of linear chain of ferroelectric-ferromagnetic crystal structure is considered. It is analyzed theoretically in the motion equation method on the pursuit of magnonic excitations,lattice vibration excitations and their interactions leading to a new collective mode of excitations,the electormagnons. In this particular work, it is observed that the magnetizations and polarizations are tunable in a given temperature ranges for some specific values of the coupling order parameter.

The dispersion characteristics for magnetostatic surface waves in a left handed (LHM)/ferrite/ metal-strip-grating structure have been investigated. We found that, the waveguide supports backward TE waves since both permittivity and magnetic permeability of LHM are negative. We also illustrated the dependence of wave frequency on the reduced wave number for a grating shielding parameter, g values restricted by the range 1 0 ≥ ≤ g. It is shown that the grating shielding parameter, g induces magnetostatic backward shorter waves. The leakage through the grating increases with the wave number. The shorter backward magnetostatic waves are guided by the thicker waveguide where the best confinement is achieved .

We study the electronic structure and a mean-field phase analysis based on the pair–pair energies derived from first-principles electronic structure calculations of AuFe and NiMo alloys. We have used the tight-binding linear muffin-tin orbitals-based augmented space recursion (TB-LMTO-ASR) method to do so. We investigate different behaviours of the two alloy systems by mapping the problems onto equivalent Ising models and then discuss the magnetic phase diagrams using the calculated pair energies. All three phases: paramagnetic, random ferromagnetic and spin glass, have been studied.

We present a solid-state synthesis of ferromagnetic lithium niobate nanoparticles (LiNbO3) and their corresponding structural aspects. In order to investigate the effect of heat treatments, two batches of samples with a heat-treated (HT) and non-heat-treated (nHT) reduction at 650 °C in 5% of hydrogen/argon were considered to investigate the multiferroic properties and their corresponding structural aspects; using magnetometry and scanning transmission electron microscopy (STEM). Results indicate the existence of ferromagnetic domains with a magnetic moment per unit cell of 5.24 × 10−3 μB; caused mainly due to voids and defects on the nanoparticle surface, as confirmed by STEM measurements.