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Near-zero magnetic shielding systems (MSSs) can provide basic experimental environments for extremely weak magnetic measurements. Reducing the internal magnetic field of MSS is the crucial element of high-sensitivity measurements, which is related to the shielding material flux. As an effective way to regulate the material remanence, degaussing reconstructs the magnetic balance with the geomagnetic field. However, previous research studies mainly focused on the optimization of material degaussing, with few considering the practical application scenarios of MSS. In this work, a numerical modeling method is proposed to realistically depict the balancing process, and the mapping relationship between the internal magnetic field of the MSS and the degaussing current is established. First, the magnetic field source analysis is carried out, and the internal magnetic field fluctuations of the MSS during degaussing are decomposed into multi-harmonic components. Then, the phase and amplitude changes of the hysteresis loop are simulated to predict the residual field. Thereafter, the effectiveness of the method is verified by a magnetic shielding cylinder. The experimental results indicate that the slight difference in material remanence has a negligible effect on the residual field. This work has potential application value in the research of degaussing technology. [ABSTRACT FROM AUTHOR]

The phenomenon of exchange bias has been extensively studied within crystalline materials, encompassing a broad spectrum from nanoparticles to thin-film systems. Nonetheless, exchange bias in amorphous alloys has remained a relatively unexplored domain, primarily owing to their inherently uniform disordered atomic structure and lacking grain boundaries. In this study, we present a unique instance of exchange bias observed in Fe–B–Nb amorphous thin films, offering insights into its origins intertwined with the system's spin-glass-like behavior at lower temperatures. The quantification of exchange bias was accomplished through a meticulous analysis of magnetic reversal behaviors in the liquid-helium temperature range, employing a zero-field cooling approach from various initial remanent magnetization states (±MR). At reduced temperatures, the appearance of asymmetric hysteresis, a hallmark of negative exchange bias, undergoes a transformation into symmetric hysteresis loops at elevated temperatures, underscoring the intimate connection between exchange-bias and dynamic magnetic states. Further investigations into the magnetic thermal evolution under varying probe fields reveal the system's transition into a spin-glass-like state at low temperatures. We attribute the origin of this unconventional exchange bias to the intricate exchange interactions within the spin-glass-like regions that manifest at the interfaces among highly disordered Fe-nuclei. The formation of Fe-nuclei agglomerates at the sub-nanometer scale is attributed to the alloy's limited glass-forming ability and the nature of the thin-film fabrication process. We propose that this distinctive form of exchange bias represents a novel characteristic of amorphous thin films. [ABSTRACT FROM AUTHOR]

The effects of La/Ho co-substitution on multiferroic characteristics were investigated for BiFeO3 ceramics together with structure evolution. The symmetry in Bi1−x(La0.65Ho0.35)xFeO3 ceramics changed from R3c to Pna21 and finally Pbnm with increasing x. Ferroelectricity was significantly improved with La/Ho co-substitution, and Pr reached the maximum of 30.9 μC/cm2 at 160 kV/cm at x = 0.16, where the R3c/Pna21 morphotropic phase boundary was determined. The weak ferromagnetism was released as the symmetry changed from R3c to Pna21, and subsequently the saturated M–H loop could be determined gradually with increasing x, and Mr increased continuously. The electric field-controlled magnetism could be characterized by the significant magnetism variation due to the electric field-induced transition of Pna21/R3c, which occurred during the poling process, and this transition became reversible by the help of annealing after poling. Compared with the situation of Bi1−xNdxFeO3 (the ion radius is the same as the effective one of La0.65Ho0.35), the present co-substituted BiFeO3 ceramics exhibited superior electric field-induced transition of Pna21/R3c with a maximum change rate of 47.03% in remanent magnetization under an electric field, which enhanced the magnetoelectric effect. [ABSTRACT FROM AUTHOR]

Pointed magnetic elements are introduced as an improvement upon rectangular strips currently employed in composite element magnetic barcodes. The coercivity of these elements, as measured using the magneto-optic Kerr effect, is found to strictly adhere to a single power law relationship with the element width, where the power law exponent is dependent on the length of the pointed region and takes values between − 0.98 and − 0.91. The steeper gradients here, along with the absence of the crossover region seen in rectangular devices, present these structures as a strict improvement in terms of potential device applications. These improvements are found to be present for all structures where the pointed region is as long as, or longer than, the magnetic element is wide. The remanent magnetization configuration, imaged using photo-emission microscopy with contrast from x-ray magnetic circular dichroism (XMCD-PEEM), is compared to the results of micromagnetic simulations. It is found to cant inward in the pointed section of the strip, aligning with the edges of the point, pinning the magnetization and giving a consistent magnetization reversal behavior for all element widths investigated. [ABSTRACT FROM AUTHOR]

Fe films with thicknesses between 17 and 95 nm were grown with a nano-sheet morphology, which enabled their high uniaxial magnetic, transport, and optical in-plane anisotropies. The top edge of the nano-sheets was directly visualized as nano-string-like structures of approximately 12.5–14 nm width and 100–300 nm length. The hysteresis loops showed a clear easy direction of magnetization in the longitudinal direction of the nano-sheets, whereas the hard direction loops were anhysteretic, with no remanence and zero coercive field. The anisotropy field exhibited values between 70 and 111 kA/m depending on the thickness of the films, with the maximum value corresponding to a 34 nm thick sample. The resistance of the films was also found to be highly anisotropic. The ratio (R⊥–R||)/R|| was ≈86%, with R|| and R⊥ being the resistances in the parallel and perpendicular directions of the nano-sheets, respectively. Likewise, the reflectivity of the samples behaved anisotropically; the ratio (IReflmax–IReflmin)/IReflmax of the intensity of reflected light by the films reached up to 61% for 34 nm thick samples, achieving the maximum value, IReflmax, when the plane of the incident light coincided with the direction of the nano-sheets and the minimum, IReflmin, when this plane was perpendicular to the direction of the nano-sheets. The origin of these anisotropic behaviors was established. These anisotropic films with high magnetization and high uniaxial anisotropies at the nanoscale can be useful for microelectronics applications, for devices such as magnetic sensors and transducers, or for ultrahigh frequency inductors. [ABSTRACT FROM AUTHOR]

This study focuses on the microstructure and magnetic properties of Mn-20at. %Ga composites prepared via high-energy ball milling and subsequent reactive sintering under a high magnetic field (HMF). XRD identified the ɛ-Mn3Ga, β-Mn0.85Ga0.15, and α-Mn phases, and their fractions determined the magnetic properties of the composites. The results revealed that HMF enhanced the fractions of both ɛ-Mn3Ga and β-Mn0.85Ga0.15 phases and decreased the fraction of α-Mn. The magnetic-field-induced enhancement effect on the reaction was mainly due to a decrease in the activation energy, which mainly affected the phase reaction at the initial stages. However, a HMF of 9–12 T suppressed the atomic diffusion between Mn and Ga, reducing the reaction-enhancing effect of the magnetic field. Compared with zero-field annealing, the 3 T in-field annealing enhanced the remanence and coercivity of the composite by 44% and 16%, respectively. In contrast, the 12 T HMF decreased the remanence but increased the coercivity to its highest value. The coercivity of the 12 T in-field samples reaches 11.09 kOe after 8 h of in-field annealing. After the in-field annealing, subsequent zero-field annealing for an appropriate duration may further increase the remanence and energy product. Enhancing the in-field annealing temperature up to 400 °C may increase the coercivity but decrease the remanence considerably. [ABSTRACT FROM AUTHOR]

We have investigated the effect of an external electric field on the magnetic properties of Co2MnAl thin films deposited on a lead magnesium niobate-lead titanate (PMN-PT) (011) substrate. Stain-induced magnetoelectric coupling affects the magnetic properties of the Co2MnAl/PMN-PT system. The piezo-strain induced by applying an external field normal to the surface induces only in-plane strain, which leads to the rotation of easy-axis orientation of Co2MnAl from [100] to [ 01 1 ¯ ] direction. The remanent magnetization states and coercivity of the Co2MnAl film vary significantly and asymmetrically with the applied voltage due to anisotropic strain originating from PMN-PT. Electrical control of magnetic anisotropy in a Co2MnAl Heusler compound at room temperature will be of interest for realizing next-generation magnetoelectric random access memory devices. [ABSTRACT FROM AUTHOR]

We report a theoretical study of the magnetic profiles of vortex pairs in dipolar coupling thin Ni 80 Fe 20 (Permalloy Py™) elliptical nanocylinders. We show that the external magnetic field route can control the magnetic phases at remanence. Although the isolated nanocylinder forms one vortex in the remanence, in the presence of another, the dipolar interaction can induce a vortex pair in each nanocylinder. Moreover, our results show that we can adjust the two pairs of the magnetic vortex via the external magnetic field route. For the major-axis route, the pair of magnetic vortices in a nanocylinder is entirely antiparallel to the pair of magnetic vortices in the other nanocylinder. In contrast, both nanocylinders' pairs of magnetic vortices are completely parallel for the minor-axis route at remanence. In this case, the magnetic patterns are the same in both nanocylinders. As an application, we present the results for a pair of identical and coaxial Py elliptical (245 × 405 × 25 nm 3) nanocylinders separated by a nonmagnetic spacer of 50 nm. [ABSTRACT FROM AUTHOR]

For bulk SmCo3 system hard-soft magnetic nanocomposites, it remains a challenge to fabricate an anisotropic magnet by forming a strong texture for the nanocrystalline SmCo3 phase. In this paper, we report the fabrication of a bulk anisotropic SmCo3/Fe(Co) nanocomposite magnet with a strong (00 l) texture for the SmCo3 phase and a small grain size of 21 nm for the Fe(Co) phase. Good results were achieved by controlling the nucleation and growth of the nanocrystals from the amorphous matrix using large stress and strain. The synthesized magnet exhibited a high-energy product of 17.0 MGOe, which was 26% larger than the reported highest value of 13.5 MGOe for SmCo3-based nanocomposites and 314% higher than 4.1 MGOe for the corresponding pure SmCo3 magnets. Moreover, these magnets possessed small remanence and coercivity temperature coefficients of α = −0.018%/°C and β = −0.24%/°C, which were much lower than those α = −0.14%/°C and β = −0.31%/°C for pure SmCo3 magnets and α = −0.073%/°C and β = −0.30%/°C for SmCo3/Fe(Co) isotropic nanocomposite. These findings are an important step toward the practical application of the SmCo3-based nanocomposite. [ABSTRACT FROM AUTHOR]

Integrating multiple functions in a single compound is still attractive and necessary to meet the demand of device miniaturization. In this work, we systemically modulate multifunctional properties in the 0.74BiFeO3–0.26(Ba0:85Ca0:15)TiO3–x wt. % MnO2 solid solution with the addition of MnO2. A highly rectangular and saturated polarization–hysteresis (P–E) loop is obtained with a large remanent polarization Pr of 49.5 μC/cm² as x = 0:8. Furthermore, the piezoelectric coefficient d33 also obviously improved with an optimized d33 = 137 pC/N by the introduction of MnO2 due to the grain size effect, the improvement of insulation, and relaxation regulation. With the addition of MnO2, the remanent magnetization Mr increases monotonically because of the enhanced exchange interactions between Fe2+and Fe3+. The results may provide an effective way to explore promising multifunctional materials in BiFeO3-based ceramics. [ABSTRACT FROM AUTHOR]

We report a theoretical study of the magnetic profiles of vortex pairs of dipolar coupled Fe nanocylinders. We consider pairs of identical and coaxial 21 nm height Fe circular nanocylinders with the diameter values ranging from 81 nm to 129 nm. We show that, even though each isolated nanocylinder holds a vortex at remanence, the dipolar interaction may inhibit the formation of vortices for small values of the nanocylinders' distance. For moderate values of the nanocylinders' distance, the formation of opposite chirality vortex pairs is favored. We show that the vortex locations, the vortex pair magnetic pattern, and the dipolar field and local field profiles may be tailored using moderate external field values along preparation routes parallel and perpendicular to the Fe uniaxial anisotropy easy axis. [ABSTRACT FROM AUTHOR]

The discovery of single-phase multiferroic materials and the understanding of intriguing physics of the coupling mechanisms between their spin and polarization are important for the next generation of multifunctional devices. In this work, we report dielectric, ferroelectric, and magnetization results of Pd-substituted room-temperature magnetoelectric multiferroic Pb(Zr0.20Ti0.80)0.7Pd0.3O3 (PZTPd) thin films. Highly c axis oriented PZTPd thin films were grown on {(LaAlO3)0.3(Sr2AlTaO6)0.7} substrates using the pulsed laser deposition technique. These films were phase pure and stabilized in a tetragonal phase. Atomic force microscopic studies indicated a homogeneous distribution of grains on the films' surface with a surface roughness (RQ) of ∼5.4 nm. A large dielectric constant of ∼1780 and a low loss tangent value of ∼0.52 were observed at 1 kHz measured at room temperature. Temperature dependent dielectric studies on Pt/PZTPd/La0.7Sr0.3MnO3 metal–insulator–metal heterostructure capacitors between 80 and 660 K indicated a diffused ferroelectric to paraelectric phase transition around 515 K. The polarization hysteresis loops observed at room temperature were attributed to its ferroelectric behavior. Saturated magnetization hysteresis loop with remanent magnetization of 1.54 emu/cm3 was obtained at room temperature. Ferromagnetic ordering in thin films was found to sustain in the entire temperature range from 5 to 395 K, as revealed from the constant behavior of the dM/dT curve with temperature. The mixed oxidation states of palladium (Pd2+/Pd4+) dispersed in the polar Pb(Zr0.20Ti0.80)O3 matrix were revealed from our high resolution x-ray photoelectron spectroscopic studies and is ascribed to the origin of ferromagnetic ordering in the film. These findings suggest that PZTPd thin films are multiferroic (ferroelectric–ferromagnetic) at room temperature. [ABSTRACT FROM AUTHOR]

The effect of CuO and MnO 2 as sintering additives on the structural, ferroelectric, and magnetic properties of 0.7 BiFeO 3 − 0.3 (Ba 0.85 Ca 0.15) TiO 3 was investigated. The addition of CuO can inhibit grain growth, and the sample possesses the maximum remanent magnetization. However, the addition of MnO 2 can promote grain growth, and the sample exhibits the maximum remanent polarization of 34 μ C / cm 2. Nevertheless, the addition of both CuO and MnO 2 can markedly enhance the magnetic properties. The magnetization measurements manifest that all the samples undergo a paramagnetic to ferrimagnetic transition arising from the existence of a net moment due to the antiferrimagnetic interactions between Fe 2 + and Fe 3 + sublattices. The enhanced magnetism of the samples with the addition of CuO and MnO 2 can be due to the enhanced superexchange interaction between Fe 2 + and Fe 3 + arising from the increased Fe–O–Fe bond angle. [ABSTRACT FROM AUTHOR]

The magnetic property of a 0.7BiFeO3-0.3TbMnO3 composite has been studied in detail and compared with that of 0.8BiFeO3-0.2TbMnO3. The magnetic properties in 0.7BiFeO3-0.3TbMnO3 are improved in manifold compared to BiFeO3. An exchange bias (HEB) is observed in both the compositions of these antiferromagnetic composites, which varies between 5 and 180 Oe with a maximum at ∼275 K. Isothermal remanent magnetization measurements at room temperature indicate the presence of an interfacial layer of a 2-dimensional dilute uniaxial antiferromagnet in a uniform magnetic field (2D DAFF). The presence of exchange bias can be explained on the basis of a strong strain-mediated magnetoelectric coupling induced exchange interaction and the creation of a 2D DAFF layer at the interface. The properties of this layer are defined by canting and pinning of BiFeO3 spins at the interface with TbMnO3 due to Fe and Mn interaction. X-ray magnetic circular dichroism confirms the presence of canted antiferromagnetic ordering of BiFeO3, charge transfer between Mn ions, and different magnetically coupled layers that play a vital role in the exchange bias. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and electrical properties of polycrystalline Y-Sc codoped BiFeO 3 (BFO) ceramics are investigated. Rietveld refinement and Raman spectroscopy analysis provide strong evidence of structural distortion without changing the structure of parent compound (rhombohedral: R3c) after codoping. Distortion due to nonmagnetic codoping marks an abrupt change in magnetic and electrical properties of BiFeO 3. Ferromagnetic property is enhanced with a maximum remanent magnetization of 0.0045 emu/g at higher Sc-concentrations. Codoping improves the ferroelectric properties [ P r = 13 μ C / cm 2 at (Y , Sc) = (0.03 , 0.05) ] due to the suppression of oxygen vacancies. The frequency-dependent dielectric properties at various temperatures are investigated. The relaxation peak shifts toward room temperature for Bi 1 − x Y x Fe 1 − y Sc y O 3 ceramics, which eventually appeared above 100 ° C for parent BFO. The suppression of relaxation peak indicates the change in conduction mechanism for codoped ceramics. The conduction process and the relaxation mechanism in parent and Y-Sc codoped BiFeO 3 are investigated with electrical modulus and impedance spectroscopy. Frequency-dependent ac conductivity at various temperatures indicates that the conduction mechanism follows the correlated barrier hopping model and is thermally activated. Temperature dependent conductivity studies at different frequencies reveal that the relaxation process in codoped ceramics is due to the long-range oxygen vacancy movement and the low loss values. [ABSTRACT FROM AUTHOR]

This report is on the observation and theory for strong mechanical strain mediated magneto-electric (ME) coupling in composites of lead zirconate titanate (PZT) and self-biased Y- or W-type hexagonal ferrites. Polycrystalline Y-type (Ni1−xZnx)2 Y, and W-type (Co1−xZnx)2 W, hexagonal ferrites for x = 0–0.4 prepared by ceramic processing techniques showed a large remanent magnetization due to uniaxial or in-plane magneto-crystalline anisotropy. The strength of ME coupling in symmetric trilayer composites of the ferrites and PZT was measured by the ME voltage coefficient (MEVC) at low-frequencies and at longitudinal electromechanical resonance. The bias magnetic field H-dependence of MEVC at low-frequencies in the composites with (Ni, Zn) Y showed hysteresis with its value under self-bias 90% or more of the value for the optimum bias field. In the case of composites with W-type ferrites, the MEVC under zero-external bias was 60%–80% of its value for the optimum bias field. Both types of composites when subjected to an ac magnetic field at the EMR frequency showed an order of magnitude enhancement in the MEVC compared to low-frequencies and the peak value at EMR for zero-bias was 90% of its value under the optimum bias. A model has been developed for the large ME response under the self-bias provided by the remanent magnetization and estimated values of MEVC are in good agreement with the data. The hexaferrite-ferroelectric composites showing ME response without the need for an external magnetic bias are of importance for use as sensors and sensor arrays of magnetic fields. [ABSTRACT FROM AUTHOR]

Epitaxial γ′-Fe4N films with different thicknesses were fabricated on Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrates by facing-target reactive sputtering. The magnetoelectric coupling (MEC) in the samples was systematically investigated. Firstly, the magnetization along different in-plane directions is tunable by the electric field. It was found that MEC in the films on PMN-PT(011) is stronger than that on PMN-PT(001) due to the different in-plane magnetic anisotropy. Moreover, the magnetoelectric coupling is strongly related to the γ′-Fe4N film thickness, which can be ascribed to the competition between the strain and spin-dependent screening effect induced MEC. Additionally, the electric-field tailored remanent magnetization of the samples gradually increases with temperature due to the thermal agitation. Besides, the electric-field effect on the out-of-plane magnetic hysteresis loops is consistent with the in-plane cases. The results are of benefit to the development of the electric-field controlled spintronic devices. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) composites that exhibit both ferroelectric and ferromagnetic properties have attracted significant attention, thanks to their potential applications, e.g., low-energy-consumption storage devices. Here, we study bulk composites based on Pb(Zr0.52Ti0.48)O3 (PZT) as a piezoelectric (PE) matrix and Fe3O4 nanoparticles (NPs) as soft ferromagnetic (FM) and magnetostrictive additives, in the form PZT-xFe3O4 with 0% ≤ x ≤ 50 wt. %, all sintered at T = 1000 °C for 2 h in air. We focus our study on a completely insulating sample x = 5% and measure its properties at room temperature upon an out-of-plane external electric field, Eex: namely, piezoelectric response [in-plane strain, S(Eex)], polarization [P(Eex)], and relaxation of the remanent magnetization, [mrem(t,Eex)], prepared upon application and removal of an external magnetic field. The peaks observed in the butterflylike S(Eex) curves at E±peak = ±6 kV/cm and the nucleation field recorded in the P(Eex) loops at the same range around E±nuc = ±6 kV/cm (both referring to the PZT PE matrix) are clearly imprinted on the relaxation behavior of the mrem(t,Eex) data (referring to the Fe3O4 FM NPs). This experimental fact proves the ME coupling between the PZT matrix and the embedded Fe3O4 NPs. We ascribe this feature to the comparable piezoelectricity of the PZT matrix and the magnetostriction of the Fe3O4 NPs that probably motivate and/or promote a strain transfer mechanism occurring at the PZT matrix-Fe3O4 NP interfaces. Our work proves that the low cost PZT-xFe3O4 composite is a promising candidate ME material for future studies, aiming to potential applications. [ABSTRACT FROM AUTHOR]

Cluster deposited Pd films exhibit ferromagnetism in the temperature range from 1.8 to 400 K. The magnetization properties are found to be dependent on the film thickness. The varying morphology of the resulting Pd film with respect to thickness suggests that cluster size, deposition energy, and substrate type are crucial for the resulting film magnetization. This is demonstrated by the characteristic ferromagnetic hysteresis with the temperature dependent saturation magnetization, remanence, and coercivity of palladium nanocluster aggregates. The temperature dependence of the saturation magnetization, remanence, and coercivity of Pd nanoclusters were measured using an ultra-high-sensitive magnetometer based on a superconducting quantum interference device, and the morphology of the samples was analyzed by tunneling electron microscopy. [ABSTRACT FROM AUTHOR]

The hysteresis loops and the magnetic reversal process of exchange-coupled Nd2Fe14B/α″-Fe16N2 bilayers, with a deviation angle of easy axis β from the applied magnetic field direction and different thicknesses of soft phase were investigated using the object-oriented micromagnetic framework. Results show that a deviation of easy axis in Nd2Fe14B/α″-Fe16N2 bilayers can affect the magnetic properties and significantly decrease the energy product and coercivity. The remanence increases, whereas the coercivity of the bilayers drops monotonically, with the increase in thickness of the soft magnetic layer (Ls). A well-oriented bilayer with Ls = 4 nm exhibits the largest maximum energy product (i.e., 881.67 kJ/m³), which is larger than that of the other common exchange spring materials that we calculated. Therefore, the proposed nanocomposite magnet is one of the most promising exchange spring systems to achieve maximum energy product. [ABSTRACT FROM AUTHOR]

To realize multiferroic and magnetoelectric properties, bi-layered nanocomposite films consisting of CoFe2O4 (CFO)/Pb1-xSrxTiO3 (PST) phases (x=0.1, 0.2, and 0.3) have been deposited on Pt/TiO2/SiO2/Si substrate by using a metallo-organic decomposition process. Both the PST perovskite and the CFO spinel phases are confirmed from X-ray diffraction patterns and Raman spectra of the composite films. The composite films exhibit room temperature multiferroic properties. The values of saturation magnetization (Ms), remanent magnetization (Mr), and coercive field (Hc) of the composite films are in the range of 108-119 kA/m, 42-51 kA/m, and 44.5-64.1 kA/m, respectively. In addition, the saturation polarization (Ps), remanent polarization (Pr), and electrical coercive field (Ec) are observed in the range of 11.3-14.4 μC/cm², 2.9-4.8 μC/cm², and 56-59.5 kV/cm, respectively. The dielectric response in the presence of applied magnetic field, Hdc∼238.6 kA/m shows a high magnetocapacitance value ∼385% at frequency 100 kHz for CFO/PST composite film with x=0.1. The maximum magnetoelectric voltage co-efficient value, αE∼380 kV/(m×T) has been achieved in the composite films with x=0.1. The influence of elastic/and or interfacial strain on multiferroic magnetoelectric properties is evident from the results. [ABSTRACT FROM AUTHOR]

We produced a high-quality hard magnetic Fe81Co2Nb1Nd10B6 alloy by melt spinning without additional treatment. The as-spun ribbons produced at a wheel speed of ~25 m/s had the best hard magnetic properties: a remanence Br, coercive force Hc, and maximum energy product (BH)max of 0.97 T, 676 kA/m, and 140 kJ/m3, respectively. The Nd2Fe14B/α-Fe nanocomposite phases had grain sizes of ~10-30 nm. We investigated how the magnetic properties changed with wheel speed, finding that they depended on the as-spun structure and magnetic structure, which changed upon over-and under-quenching from the melt. [ABSTRACT FROM AUTHOR]

Crystal structure, microstructure, local ferroelectric, and magnetic properties of the Bi0.9Nd0.1Fe1-xTixO3 samples have been investigated at room temperature to reveal the effect of Ti4+ doping on the multiferroic behavior of the lanthanide-modified compound representing a polar (space group R3c) antiferromagnetic phase of the Bi1-xLnxFeO3 perovskites. Ti doping results in a gradual suppression of the rhombohedral distortions, however, symmetry of the crystal structure remains the same in the entire concentration range allowing the single-phase perovskites to be obtained (x⩽0.08). The doping tends to reduce existing lone-pair cation-driven polar displacements, thus giving rise to a decrease of the ferroelectric polarization in the Bi0.9Nd0.1Fe1-xTixO3 (x→0.08) series. A drastic (from ~10 μm for x=0 to ~1 μm for 0.02⩽x⩽0.08) decrease of the average grain size induced by the doping is accompanied by the formation of a ferroelectric domain structure with the average domain width of ~40 nm. Finally, the doping was shown to induce an antiferromagnetic to weak ferromagnetic transformation. The maximum remanent magnetization observed in the Bi0.9Nd0.1Fe1-xTixO3 series at x~0.05 coincides with the locked magnetization releasing upon the magnetic field-induced suppression of the magnetic cycloid in pure BiFeO3. [ABSTRACT FROM AUTHOR]

Magnetic properties of compacted Sm0.1Ca0.9MnO3 particles with 25 and 60 nm average sizes have been investigated. Particular attention has been paid to Griffiths-like features at temperatures above magnetic transition temperature TC and to the system glassiness at low temperatures. Griffiths-like features in inverse magnetic susceptibility of Sm0.1Ca0.9MnO3 nanoparticles have been linked to the presence of short range ferromagnetically correlated spin clusters above TC. Glassy behavior has been revealed in temperature and frequency dependence of ac-susceptibility, temperature and field dependence of thermoremanent and isothermoremanent magnetization, and time decay of the remanent magnetization. Experiments revealed the major impact of the glassy component on magnetic properties of investigated nanoparticles. The magnetic relaxation associated with glassy features was found to be much more pronounced in smaller particles, where a formation of collective state in an ensemble of phase separated nanoparticles may take place. Thermomagnetic irreversibility found in Sm0.1Ca0.9MnO3 nanoparticles has been linked to martensitic strain effects. [ABSTRACT FROM AUTHOR]

A measurement technique is depicted that allows one to analyze the direction as well as the distribution of the remanence (or remanent magnetization) of permanent magnets. To this end, the magnetic field is measured at several positions around the magnet, and the magnet is subdivided into multiple cells. Then, an efficient method is presented how the remanence vectors of these cells are computed from the measurement values by means of finite element simulations. Finally, the measurement technique is applied to permanent magnets used in magnetically biased chokes which demonstrates the new possibilities and the practical applicability. [ABSTRACT FROM AUTHOR]

A preparation of Pr-Fe-B thick-film magnets by using a PLD (Pulsed Laser Deposition) method with the energy density at approximately 50mJ/m2 using the laser power of 2W was effective to obtain the required magnetic properties for the application to a multi-polarly magnetized rotor. The isotropic films mainly consisted of Pr2Fe14B magnetic phase whose saturation magnetization is approximately 1.56 T, however the remanence (Br) showed higher than 0.9 T. The obtained value of Br was considered to be attributed to a remanence enhancement due to the interaction of Pr2Fe14B hard magnetic phases. Resultantly, the coercivity and (BH)max of the samples exceeded 600 kA/m and 115 kJ/m3, respectively, which were larger than that of previously reported PLD-fabricated isotropic rare-earth based thick-films. [ABSTRACT FROM AUTHOR]

The effect of quench rate on nanostructure and magnetic properties of PrCo5 alloy has been investigated. The increase of quench rate through wheel speed in melt spinning suppresses the formation of the secondary Pr2Co17 and Pr5Co19 phases with low magnetocrystalline anisotropy field and refines the nanostructure. This significantly improves the coercivity, remanence, and energy product. For example, increasing the wheel speed from 30 m/s to 70 m/s increases the coercivity and energy product from 3.2 kOe and 4.0 MGOe to 10.3 kOe and 13.7 MGOe, respectively. The magnetic hardening mechanism appears to be a mixture of reverseddomain- nucleation and domain-wall-pinning. The temperature coefficient of coercivity for the 70 m/s sample is -0.16%/K from 300 to 700 K, which is better than that of sintered SmCo5 magnets. Low temperature coefficients of coercivity and remanence indicate that rapidly quenched PrCo5 ribbons may be suitable for bonded magnets with high operation temperature. [ABSTRACT FROM AUTHOR]

The effect of quench rate on nanostructure and magnetic properties of PrCo5 alloy has been investigated. The increase of quench rate through wheel speed in melt spinning suppresses the formation of the secondary Pr2Co17 and Pr5Co19 phases with low magnetocrystalline anisotropy field and refines the nanostructure. This significantly improves the coercivity, remanence, and energy product. For example, increasing the wheel speed from 30 m/s to 70 m/s increases the coercivity and energy product from 3.2 kOe and 4.0 MGOe to 10.3 kOe and 13.7 MGOe, respectively. The magnetic hardening mechanism appears to be a mixture of reverseddomain- nucleation and domain-wall-pinning. The temperature coefficient of coercivity for the 70 m/s sample is -0.16%/K from 300 to 700 K, which is better than that of sintered SmCo5 magnets. Low temperature coefficients of coercivity and remanence indicate that rapidly quenched PrCo5 ribbons may be suitable for bonded magnets with high operation temperature. [ABSTRACT FROM AUTHOR]

Structure and magnetic properties were studied for Tm2(Co1-xFex)17 bulk nanocrystalline magnet synthesized by spark plasma sintering technique. X-ray diffraction results indicate both ingot and sintered magnet of Tm2(Co0.7Fe0.3)17 alloy exhibit hexagonal Th2Ni17 type structure. The microstructure of the magnet is composed of Th2Ni17 type nanograins with an average size of 35 nm detected by transmission electron microscopy and selected area electron diffraction patterns. Magnetic measurement shows that the remanence of the magnet is higher at 573 K than at 300 K, indicating there is a positive remanence temperature coefficient in the magnet. The anisotropy field of Tm2(Co0.7Fe0.3)17 alloy is 3.8 T, which is much higher than the HA of 2.3 T for the pure Tm2Co17alloy. The coercivity of the sintered magnet increases from 0.25 to 0.354 T after optimal annealing. [ABSTRACT FROM AUTHOR]

We report on new high-saturation induction, high-temperature nanocomposite alloys with reduced glass formers. The amounts of the magnetic transition metals and early transition metal growth inhibitors were systematically varied to determine trade-offs between higher inductions and fine microstructures with consequently lower magnetic losses. Alloys of nominal composition (Fe65Co35)79.5+xNb4-xB13Si2Cu1.5 (x=0-4) were cast into a 28 mm wide, 20 μm thick ribbon from which toroidal cores were wound. Inductions and magnetic losses were measured after nanocrystallization and stress relief. We report technical magnetic properties: permeability, maximum induction, remanence ratio, coercive field, and high frequency magnetic losses as a function of composition and annealing temperature for these alloys. Of note is the development of maximum inductions in excess of 1.76 T in cores made of alloys with the x=4 composition and maximum inductions in excess of 1.67 T in alloys with the x=3 composition, which also exhibit power losses smaller than 10 W/kg at 0.2 T induction levels in 20 kHz fields. We discuss optimization of induction with chemistry and correlate the microstructures with losses. [ABSTRACT FROM AUTHOR]

A method, a material system, and the physics for tailoring artificial magnetic field landscapes on micron and submicron length scales over a topographically flat surface in remanence are presented. KeV-He+ ion bombardment induced magnetic patterning was used for the creation of in-plane magnetized domains in Exchange Bias layer systems. This technology sets defined magnetic domain wall charges between the in-plane magnetic domains by individually set domain properties (magnitude and direction of anisotropy parameters) on both sides of the domain wall. The magnetic surface charge distribution was analyzed by magnetic force microscopy and compared to micromagnetic simulations. [ABSTRACT FROM AUTHOR]

The converse magnetoelectric effect in poly-crystalline Z-type, Sr3Co2Fe24O41, and M-type, SrCo2Ti2Fe8O19 (SCTFO), hexaferrite materials are reported. The change in remanent magnetization (Mr) for M-SCTFO sintered in oxygen and sintered in air is similar and approximately equals to ∼3% in 13 kV/cm electric field and for Z-type is ∼12% in ∼10 kV/cm electric field. The measured magnetoelectric coupling coefficient, α, values at room temperature for Z-type and M-type hexaferrites sintered in O2 were measured to be 7.6 × 10-10 sm-1 and 2.4 × 10-10 sm-1, respectively. Sintering the M-type in air reduced to 1.7 × 10-10 sm-1. As it is well known, lack of oxygen in local oxygen sites implies lower resistivity and a modified magnetic structures or state. However, in magnetoelectric hexaferrites, there is an additional effect due to lack of oxygen, and the spin spiral configuration is significantly modified to lower the induced magnetization upon the application of a DC voltage or electric field. [ABSTRACT FROM AUTHOR]

As a fundamental study of thermally assisted recording, remanence coercivity at recording speed and the energy barrier for magnetization switching for granular media were evaluated as a function of temperature T. We characterized those for CoPtCr-oxide granular media as a trial examination. Remanence coercivity was measured at measurement time t′ of 1 s (using an electromagnet) and 10-5 s (pulse field); they were defined, respectively, as Hr and HrP for T of 300-473 K. Assuming that the value of t′ at a recording speed is 1 ns and the value of remanence coercivity at the recording speed, Hr(1 ns), was evaluated by fitting Hr and HrP to Sharrock's equation. Moreover, the values of the energy barrier for magnetization switching, ΔE, were estimated. The value of Hr(1 ns) at T = 573 K, which is a typical temperature for thermally assisted recording, as estimated by extrapolation was about 6.2 kOe for the single medium and 5.5 kOe for the stacked medium. These values were about 1 order of magnitude larger than those of Hr at T = 573 K. Moreover, the reduction ratio of ΔE on increasing T showed good agreement with that of perpendicular uniaxial magnetic anisotropy, Ku. These results indicate that a large Ku reduction on increasing T was necessary to enhance the reduction of recording coercivity at elevated recording temperatures. [ABSTRACT FROM AUTHOR]