Hysteretic Magnetic Properties Research Articles

The Magnetic Properties of a NdFeB Permanent Magnets Prepared by Selective Laser Sintering

—The additive manufacturing of functional materials has a number of advantages over the sintering, which consist in the possibility of fabricating near-net-shape and locally forming the properties. In the present study, the effect of synthesis parameters on the phase composition and magnetic hysteretic properties of single-layer Nd2Fe14B-based permanent magnets synthesized by selective laser sintering is investigated. The causes for the effect of synthesis parameters on the magnetic hysteretic properties are considered. The possibility of reaching a coercivity of single-layer magnets of 19.5 kOe, which are free of heavy rare-earth metals, is demonstrated.

FeTiB film materials: Dependence of the magnetic properties and magnetic structure on the phase and structural states

The Fe99.2÷56.6Ti0÷13.2B0÷34 films were prepared by dc magnetron deposition on glass substrates. X-ray diffraction analysis was used to determine the phase composition, volume fractions of formed crystalline phases, their grain sizes and microstrains on the grain scale. The magnetic hysteretic properties, saturation induction Bs (2.1–0.3 T), coercive field Hc (0.6–6 kA/m), relative remanence Br/Bs (0.07–0.37), were determined using measured hysteresis loops. Their shapes indicate the existence of intergranular exchange interaction in all studied films. The magnetic structure parameters of the films were determined by correlation magnetometry. All films are characterized by a stochastic magnetic structure. The magnetic properties and the magnetic structure parameters of the films are substantiated by their phase and structural states. The values of the local parameters of the magnetic structure (rms local anisotropy field D1/2Ha and exchange field HR) follow the parameters of the grain (lattice parameter and grain size), while the macroscopic parameters (Hc and rms stochastic domain anisotropy field D1/2<Ha> ) have a more complex behavior.

Effect of Heat Treatment on the Magnetic Hysteretic Properties of an Isotropic Hard Magnetic Fe–30Cr–14Co Alloy

Effect of Heat Treatment on the Magnetic Hysteretic Properties of an Isotropic Hard Magnetic Fe–30Cr–14Co Alloy

Iron loss evaluation of magnetic materials excited by a SiC inverter with a Schottky barrier diode wall-integrated trench MOSFET

This study examines the impact of the different diode characteristics on the magnetic hysteretic and iron loss properties of a conventional non-oriented (NO) silicon steel sheet core under silicon carbide (SiC) inverter excitation. We compared the magnetic properties of the magnetic core excited by the inverter using the developed Schottky barrier diode (SBD) wall-integrated trench MOSFET (SWITCH–MOS), which has a low on-voltage Von diode, with those excited by the inverter using a conventional U-shaped trench gate MOSFET (UMOS), which has a body PiN diode with high Von. This study shows for the first time that the shape of the minor loop and iron loss properties depends strongly on only the diode characteristics in the inverter. The iron loss of magnetic materials excited by the SWITCH–MOS inverter with the low-Von diode (i.e., the built-in SBD) was less than that in the case of using the conventional UMOS with a high-Von diode (i.e., the body PiN diode). That is, the SWITCH–MOS with built-in SBD can reduce not only the switching loss, but also the iron loss in magnetic materials such as motor cores.

Effect of Heat Treatment on the Magnetic Hysteretic Properties of an Anisotropic Hard Magnetic Fe–28Cr–10Co–0.5W Powder Alloy

Abstract—The magnetic hysteretic properties (residual induction Br, coercive force HcB, maximum energy product (BH)max) of an anisotropic hard magnetic Fe–28Cr–10Co–0.5W powder alloy are estimated after heat treatment under the conditions chosen by the Statgraphics XVI Centurion software. The magnetic hysteretic properties (Br = 1.336 T, HcB = 46.1 kA/m, (BH)max = 44.1 kJ/m3) reached after the optimum heat treatment exceed the analogous properties of one of the main industrial alloys, namely, 25Kh15KYuBF (State Standard GOST 24897–81), by more than 15%; in this case, the cobalt content in the alloy under study is one third less than that in the industrial alloy. Because of this, the hard magnetic Fe–28Cr–10Co–0.5W powder alloy can be recommended for industrial development.

Metastable states in high carbon C–(Fe, Ni, Co) films obtained by three-electrode ion-plasma sputtering

The effect of ion-plasma deposition on the structure of high-carbon films (at. %) Fe–(20–84) % С, Co–(5–52) % С, Ni–(7–61) % С was investigated. The lattice periods and crystallite sizes of nonequilibrium phases in the as-deposited state and after heating are determined. The temperatures of the beginning and end of the decay of metastable phases during heating at a constant speed are established. The transition from an amorphous to an equilibrium crystalline state in Fe–C films passes through the stage of formation and subsequent decomposition of an intermediate, metastable hcp phase of variable composition. The electrical and hysteretic magnetic properties of the films were measured in the as-deposited state and after heat treatment. The compositions and conditions for producing films with low values of the temperature coefficient of electrical resistance and high coercive force are established. Thus, high-carbon films of Ni–61% C in the as-depoteted state and Fe–69% C films after heating to 900 K are characterized by small TCR values (± 10−6 К−1) over a wide temperature range.

Magnetic Hysteretic Properties of an Fe–25Cr–12Co Powdered Hard Magnetic Alloy

The magnetic hysteretic properties of an Fe–25Cr–12Co powdered hard magnetic alloy have been studied as a function of heat-treatment conditions. The optimization of heat treatment, including thermomagnetic process, and the determination of the optimum magnetic hysteretic properties have been performed using the Statgraphics Centurion XVI software. The following parameters are obtained after the optimum heat treatment: the residual induction is up to Br = 1.425 T, the coercive force is HcB up to 46.45 kA/m, and the maximum energy product is (BH)max = 45.2 kJ/m3. Various optimum heat-treatment conditions are required to achieve the optimum values of Br, HcB, and (BH)max.

Effect of the Charge Mixing Time on the Magnetic Hysteretic Properties of a Hard Magnetic Powder Fe–30% Cr–8% Co Alloy

The elemental mapping of a hard magnetic powder Fe–30Cr–8Co alloy prepared at different charge mixing times allows us to find that a homogeneous distribution of the components is reached upon mixing for 60 min. The dependence of the magnetic hysteretic properties of the powder Fe–30Cr–8Co alloy samples sintered at 1200°C on the mixing time exhibits logarithmic behavior. At the same time, the magnetic hysteretic properties of the same samples sintered at 1400°C are higher because of lower residual porosity and are independent on the charge mixing time.

Structure and magnetic hysteresis Properties of NdFe11 Ti based alloys and their nitrides after different methods of obtaining

We have studied the effect of synthesis methods on the structural state and magnetic hysteresis properties of the NdFe11Ti compound with ThMn12 structure obtained by arc- melting, annealing, melt spinning and nitriding. We found prolonged high-temperature annealing and melt spinning form a single-phase state. However, the grain size of the alloy after melt spinning is 1000 times as less which leads to high magnetic properties as compared to annealing. Nitriding increases the magnetic hysteretic properties after both annealing and melt spinning.

Physical properties and structure of vapor-quenched immiscible alloys

The method of modernized ion-plasma sputtering produced metastable states, including nanocrystalline and amorphous phases in films of Fe-Ag, Fe-Bi, Fe-Ag-Bi, Fe-Co-Ag and Ni-Ag alloys whose components do not mixed in the liquid state. The periods of the crystal lattices and the dimensions of the crystallites of the nonequilibrium phases in the fresh-sputtered state and after the heating are determined. The temperatures of the beginning and the end of the decomposition of metastable phases are established when heated at a constant rate. The electric and hysteretic magnetic properties of films in freshly dusted and thermally processed states are measured. The compositions and conditions for obtaining films with low values of the temperature coefficient of electrical resistivity (~ 10-5 K-1) and high coercive force (HC ~ 150 kA/m) are established. Such films can be promising for use as thin-film precision resistors and magnetic information carriers with an increased recording density.

Magnetic Hysteretic Properties of a Powdered Fe–27Cr–10Co–1Mo Hard Magnetic Alloy

The magnetic hysteretic properties of an Fe–27Cr–10Co–1Mo (27Kh10K1M) magnetic hard alloy are studied. Residual induction Br (up to 1.36 T), coercive force HcB (up to 45.4 kA/m), and maximum energy product (BH)max (up to 44 kJ/m3) have been evaluated using the Statgraphics Centurion XVI software package after optimum heat treatment. The obtained data are higher than those of a commercial iron–chromium–cobalt 25Kh15KA alloy (Russian Standard GOST 24897–81) by 15–20% on average. Different optimum heat treatment of the alloy is shown to be required to obtain the optimum values of its residual induction Br, coercive force HcB, and maximum energy product (BH)max.

Atomic-Force Microscopic Study of the Surface Morphology of the Nd2Fe14B Alloys Prepared by Various Techniques

Atomic force microscopy is used to study the nanostructured state of a number of Nd2Fe14B alloys. The starting alloys are synthesized in an argon atmosphere using an induction furnace. The nanostructured state of the Nd2Fe14B alloys is reached by two techniques, namely, severe plastic deformation and melt quenching; combined treatment, which includes severe plastic deformation of melt-quenched ribbons and subsequent annealing, is also used. The surface morphology of all studied samples is studied. These are used to interpret the magnetic hysteretic properties of the samples prepared by the different techniques.

Magnetic Hysteretic and Mechanical Properties of a 31Kh20K3M Alloy with an Increased Carbon Content

An Fe–31Cr–20Co–3Mo (31Kh20K3M) alloy containing 0.09 wt % C, which is almost twice as much as its maximum content according to GOST 24897–81, has been studied to verify the influence of the carbon content on the magnetic hysteretic properties of hard magnetic high-chromium Fe–Cr–Co alloys. The optimal heat treatment, including thermomagnetic treatment, results in the average values of residual magnetic induction Br = 0.96 T and coercive force HcB = 63 kA/m and the maximum energy product (BH)max = 29 kJ/m3. Some heat treatment regimes give Br = 1.03 T, HcB = 72 kA/m, and (BH)max = 31 kJ/m3. In addition, for isotropic alloy samples, the following average values are obtained: Br = 0.71 T, HcB = 56 kA/m, and (BH)max = 15 kJ/m3. These magnetic hysteretic properties of the 31Kh20K3M alloy with an increased carbon content are similar to those of a powder 30Kh21K3M alloy with the minimum carbon content.

Зависимость магнитных гистерезисных свойств Fe 􀀀 30Cr 􀀀 8Co порошкового сплава от временных условий смешивания исходной и температуры спекания

Зависимость магнитных гистерезисных свойств Fe 􀀀 30Cr 􀀀 8Co порошкового сплава от временных условий смешивания исходной и температуры спекания

Effect of compositional ordering on the hysteretic magnetic properties of a cobalt-based amorphous alloy

An investigation of Co69Fe3.7Cr3.8Si12.5B11 amorphous alloy shows that thermally reversible isotropic short-range compositional ordering and clustering can lead to the degradation of hysteretic magnetic properties (HMPs). At temperatures below the Curie temperature (260°С), the degradation of HMPs is caused by thermally reversible directional ordering and reduces the mobility of domain boundaries. Clusterization, a thermally irreversible process observed via small-angle X-ray scatterimg, affects HMPs only during sample annealing immediately after quenching.

Surface anisotropy and particle size influence on hysteresis loops in [formula omitted] nanoparticles: A simulation approach

Thermal and hysteretic magnetic properties of La2/3Ca1/3MnO3 nanoparticles were studied using Monte Carlo simulations, with emphasis on the influence of anisotropy. In this work, several nanoparticle sizes ranging from 2.32 to 11.58nm were analyzed and their properties were compared to those of the bulk material. The magnetic behavior of the material was modeled using the three dimensional Heisenberg model with nearest neighbor interactions. Furthermore, both uniaxial and Néel anisotropies were considered for core and surface magnetic sites respectively. Deviations in the critical temperature and coercive field were observed for nanoparticles when compared with those of the bulk material. In addition to these properties, the special spin configurations that arise from the competition between the exchange, anisotropy and external magnetic field were also studied. All these effects are interpreted in terms of the surface properties such as the Néel anisotropy and the decrease in the coordination number.

The formation of hysteretic magnetic properties in amorphous alloys of various classes upon thermomagmetic treatment in a transverse magnetic field

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT⊥) on the permeability of the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with such a low saturation magnetostriction (λs 10–7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed (Ksq > 0.90). It has been revealed that the permeability μ4 (H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop Ksq,m in the range of 0.2 ≤ Ksq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ4 (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe57Co31Si2.9B9.1 with λs = 35 × 10–6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.

Effect of bending stresses on the high-frequency magnetic properties and their time stability in a cobalt-based amorphous alloy with an extremely low magnetostriction

An unusual effect of the stresses of bending (toroidal sample diameter D) on the hysteretic magnetic properties (Hc, μ5) of an amorphous Co69Fe3.7Cr3.8Si12B11 alloy with an extremely low magnetostriction (|λs| ≤ 10–7) is revealed. These properties are measured in a dynamic regime at a magnetic-field frequency f = 0.1–20 kHz. The coercive force of the alloy Hc weakly depends on D at low frequencies (f < 1 kHz), and permeability μ5 (H = 5 mOe), in contrast, is independent of D at high frequencies and is dependent on D at low frequencies. The samples subjected to high-temperature (390°C) annealing followed by water quenching exhibit “anomalous” dependences: permeability μ5 increases with decreasing toroidal sample radius, i.e., with increasing bending stresses. The detected dependences are related to the fact that magnetization reversal via the displacement of rigid domain walls is predominant at low frequencies and during static measurements and magnetization reversal via the displacement of flexible domain walls is predominant at high frequencies.

Do micromagnetic simulations correctly predict hard magnetic hysteresis properties?

Micromagnetic calculations using the finite element technique describe semi-quantitatively the coercivity of novel rare earth permanent magnets in dependence on grain size, grain shape, grain alignment and composition of grain boundaries and grain boundary junctions and allow the quantitative prediction of magnetic hysteretic properties of rare earth free magnets based on densely packed elongated Fe and Co nanoparticles, which depend on crystal anisotropy, aspect ratio and packing density. The nucleation of reversed domains preferentially takes place at grain boundary junctions in granular sintered and melt-spun magnets independently on the grain size. The microstructure and the nanocompostion of the intergranular regions are inhomogeneous and too complex in order to make an exact model for micromagnetic simulations and to allow a quantitative prediction. The incoherent magnetization reversal processes near the end surfaces reduce and determine the coercive field values of Co- and Fe-based nanoparticles.

Effect of bending stresses on the dynamic magnetic properties of the amorphous Co69Fe3.7Cr3.8Si12.5B11 alloy with a near-zero magnetostriction

When studying the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with a near-zero magnetostriction (|λs| ≤ 10−7), uncommon (anomalous) effects of bending stresses (of the diameter D of toroidal samples) on the hysteretic magnetic properties (Hc, μ5) measured in a dynamic regime at frequencies f of the ac magnetic field from 0.1 to 20 kHz have been revealed. At low frequencies (f < 1 kHz), the coercive force Hc of the alloy is almost independent of D. The permeability μ5 (H = 5 mOe) is independent of D at high frequencies and depends on D at low frequencies. In samples subjected to high-temperature annealing (390°C) with subsequent water quenching, uncommon regularities are observed; the permeability μ5 increases with decreasing radius of the toroidal samples, i.e., with increasing bending stresses.