Small Hysteresis Loss Research Articles

Tuning martensitic transformation and magnetocaloric effect with Bi substitution in MnCo1-xBixGe alloys

In this work, the substitution of Bi for Co atoms in MnCo1-xBixGe (x = 0.01, 0.02, 0.04, 0.06, 0.08, 0.1) alloys was prepared. The crystal structure, magnetic properties, and magnetocaloric effect have been analyzed. By tuning the Bi-content in MnCoGe alloys, the reduction of martensitic transformation (MT) temperature and the presence of a first-order magnetostructural transition (MST) were observed. Magnetic field-induced MT indicates that the magnetic field is much harder to drive MT compared to the temperature. With the Bi-content for 0.01 ≤ x ≤ 0.06, orthorhombic-type phase and hexagonal-type phase coexist. Furthermore, we observed an increase in the fraction of the hexagonal-type phase and a corresponding decrease in the fraction of the orthorhombic-type phase. It is beneficial to the refrigeration capacity for the isothermal magnetization curves M(H) on magnetization and demagnetization procedures with small magnetic hysteresis loss. With a magnetic field of 5 T, magnetocaloric effect (MCE) can be observed involving magnetic entropy change (-ΔSM) of 26.42 J kg−1 K−1 for x = 0.06 and refrigeration capacity (RC) of 259.78 J kg−1 for x = 0.01. Thus, this material is considered a fabulous candidate for magnetic refrigeration cooling applications at room temperature.

High-performance FeSiAl soft magnetic composites achieved by confined solid-state reaction

Soft magnetic composites (SMCs) consisting of insulated metallic magnetic particles are critical materials in modern electronics. However, the simultaneous optimization of power loss and permeability for SMCs remains challenging due to the vulnerable insulation layer inside. Here, we succeed in fabricating FeSiAl SMC by confined solid-state reaction between TiO2 and FeSiAl matrix, which leads to the formation of homogeneous and lattice-matched Al2O3 layer and brings about effective electrical insulation of FeSiAl particles. TiO2 can progressively release O atoms and confine the solid-state reaction strictly within the interfacial region. Meanwhile, itself becomes ferromagnetic with deficient oxygen, resulting in alleviated magnetic dilution. Fast domain wall displacement and small hysteresis loss are directly observed by in-situ Lorenz transmission electron microscopy. The obtained FeSiAl SMC exhibits low power loss of 130 mW·cm−3 (50 mT, 100 kHz) and high effective permeability of 143, which is desired in energy-saving and high-efficiency devices. This work relates the interfacial behavior with magnetic properties and highlights a new strategy for fabricating high-performance SMCs.

Hysteresis loss and field dependence of magnetic entropy change of Zn-doped Mn5Ge3 system

In this work, a series of Mn5Ge3-xZnx samples were prepared by the arc-melting method. The Rietveld structure refinement of the powder XRD spectrum was performed using the FullProf program. The lattice parameters and cell volume increase with the doping of Zn atoms. From the magnetization curve at 5 K, the compounds show a decreased magnetic moment of the Mn atom with increasing Zn content, resulting from mixing the 3d electronic state of Mn atoms and the 3d electronic state of Zn atoms. The small hysteresis loss and soft ferromagnetism of Mn5Ge3-xZnx indicate that it is suitable for magnetic refrigeration. Thermomagnetic M(T) curves show an increase in thermal hysteresis concurrent with increasing Zn concentration, which is verified by the DSC curve. It is found that the magnetic entropy change and effective magnetic moment decrease with the increase of Zn content, which can be attributable to the doping of Zn atoms resulting in the weakening of the exchange interaction between Mn-Mn atoms and the decrease of magnetic entropy change. In addition, the specific power-law relationships between the magnetic entropy change, the maximum magnetic entropy change, the relative cooling capacity, and the magnetic field of this system were determined, which provides a tool for evaluating the performance of the magnetic refrigerant in the entire magnetic field range. Finally, the specific heat was calculated by the magnetic entropy change obtained by the experiment, and the specific heat curve proves that the sample undergoes a second-order phase transition, consistent with the results of Arrott plots. The TC obtained by the specific heat -ΔCP−T curve is in good agreement with the TC obtained by the magnetic measurement, revealing that TC obtained by the specific heat is also an effective method.

High energy-storage density and efficiency in PbZrO3-based antiferroelectric multilayer ceramic capacitors

The utilization of antiferroelectric (AFE) materials is commonly believed as an effective strategy to improve the energy-storage density of multilayer ceramic capacitors (MLCCs). Unfortunately, the inferior energy conversion efficiency (η) leads to high energy dissipation, which severely restricts the broader applications of MLCCs due to the increased probability of materials and/or devices failure. Herein, AFEs featuring large polarization response and small hysteresis loss are proposed to make up for deficiencies. Guided by this proposal, (Pb0.94La0.04)(Zr0.69Sn0.30Ti0.01)O3 AFE MLCC (abbreviated as M2) are manufactured. An ultrahigh Wrec of 16.1 J/cm3 and an excellent η of 90.9% are achieved simultaneously. Additionally, a great discharge energy density (Wdis) of 8.8 J/cm3 and a large power density (PD) of 165.6 MW/cm3 are obtained synchronously. Noticeably, M2 exhibits excellent frequency-insensitive, temperature-bearable, and fatigue cycle-endurable energy-storage performances and/or charge-discharge properties. These results indicate that M2 has a promising prospect in advanced power electronic and/or pulsed power systems.

Tuning phase transitions and optimization of the magnetocaloric effect in Ho(Co<sub>1–</sub><sub><italic>x</italic></sub>Mn<sub><italic>x</italic></sub>)<sub>2</sub> alloys

<p indent="0mm">In magnetic refrigerants, tuning the materials to the first-order/second-order borderline is expected to equip the material with the advantages of the first- and second-order transitions. In this work, we performed a systematic study on the nature of the phase transition, the magnetic entropy change, and the hysteresis loss in the Mn-doped Ho(Co_1–_{<italic>x</italic>}Mn_{<italic>x</italic>})₂ alloys. We found that at <italic>x</italic> = 0.02, the material was close to the borderline of the first-order/second-order transition and exhibited a large magnetocaloric effect along with a small hysteresis loss. At <italic>x</italic>&gt;0.02, the phase transition in the sample became a second-order type, and the magnetocaloric effect was greatly reduced. These results indicate that tuning the nature of phase transition in the RCo₂-based magnetic material is an effective strategy of optimizing its magnetocaloric performance.

Increasing working temperature span in Ni-Mn-Sn-Co alloys via introducing pores

Enhanced magnetic refrigeration performance via introducing pores in a ferromagnetic shape memory Ni-Mn-Sn-Co alloy was demonstrated. The Ni40.7Mn42.9Sn10.4Co6.0 foam, with a porosity of 56% created by replication casting technique, exhibited reduced thermal hysteresis because of the high specific surface area. A maximum magnetic entropy change (ΔSM) 4.7 J/kg·K with a very wide working temperature span (ΔTFWHM) 40 K under 5.0 T were found in the annealed foam. Furthermore, the foam showed a small hysteresis loss (AHL) 17.4 J/kg under 5.0 T. As a result, refrigeration capacity (RC) 155 J/kg and relative cooling power (RCP) 188 J/kg were produced.

On the Fatigue Behavior of Nanocrystalline NiTi Shape Memory Alloys: A Review

This paper presents a review of the research on the fatigue performance of superelastic polycrystalline nanocrystalline NiTi shape memory alloys (nc NiTi SMAs). A brief introduction to some focal definitions and basic concepts of fatigue measurement and response in NiTi SMAs were given. Results found in the literature on fatigue in nc NiTi SMAs are discussed. Mechanical behavior and energy dissipation capacity of nc NiTi SMAs are explored and collectively compared with coarse-grained NiTi SMAs, along with an assessment of the influence of grain size refinement and thermomechanical treatments. Several conclusions and suggestions are made, including that nc NiTi SMAs exhibit larger functional fatigue resistance, lower crack tolerance, higher superelasticity, and smaller hysteresis loss.

Effect of Yttrium on Microstructure and Magnetocaloric Properties in La1−xYxFe11.5Si1.5 Compounds

The effects of Y on the phase composition and magnetocaloric effect in La1−xYxFe11.5Si1.5 compounds were studied. Y2Fe17-type phase and α-Fe phase appear in the annealed La1−xYxFe11.5Si1.5 compounds when x ≥ 0.07 due to small solid solubility of Y in NaZn13 phase. Y2Fe17 phase obstructs the formation of the 1:13 phase, leading to the decrease of magnetic entropy changes. But for x &lt; 0.1, La1−xYxFe11.5Si1.5 compounds exhibit high magnetic entropy changes and low hysteresis loss compared with that of LaFe11.5Si1.5. Consequently, the La1−xYxFe11.5Si1.5 compounds (x &lt; 0.1) are useful to realize large magnetocaloric effect with smaller hysteresis loss.

Molecular Dynamics Simulation Study of Polymer Nanocomposites with Controllable Dispersion of Spherical Nanoparticles.

Through coarse-grained molecular dynamics simulation, we construct a novel kind of end-linked polymer network by employing dual end-functionalized polymer chains that chemically attach to the surface of nanoparticles (NPs), so that the NPs act as large cross-linkers. We examine the effects of the length and flexibility of polymer chains on the dispersion of NPs, and the effect of the chain length on the stress-strain behavior and the segment orientation during the deformation process. We find that the stress upturn becomes more prominent with the decrease of the chain length, attributed to the limited extensibility of the chain strand connecting two neighboring NPs. In addition, this end-linked polymer nanocomposite (PNC) is shown to have a temperature-dependent stress-strain behavior that is contrary to traditional physically mixed PNCs, whose mechanical properties deteriorate with increasing temperature. This is due to the stability of the dispersion of NPs and higher entropic elasticity at higher temperature for the former, while the latter has poorer interfacial interaction at higher temperature, leading to less reinforcing efficiency. By imposing a dynamic oscillatory shear deformation, we obtain a dynamic hysteresis loop for end-linked and physically mixed dispersions. Interestingly, the end-linked system possesses a much smaller hysteresis loss than does the physically mixed system, with the latter exhibiting a more prominent decrease with increasing temperature, due to less interfacial contact. Our results demonstrate that end-linked PNCs combine attractive static and dynamic mechanical properties and exhibit an unusual response to temperature, which could find potential applications in the future.

Magnetocaloric Effect with Very Small Magnetic Hysteresis Losses of CoMn1−x Ti x Ge Alloys

The effects of Ti substitution for Mn and heat treatment on structural, magnetic, and magnetocaloric properties of CoMnGe alloy have been investigated using electron microscopy, X-ray diffraction, calorimetric, and magnetic measurements. According to X-ray diffraction measurements, CoMn1−x Ti x Ge alloys are in a single phase hexagonal structure at room temperature. It is found that the as-cast CoMn0.95Ti0.05Ge alloy shows a magnetostructural phase transition close to room temperature. The transition shows a large magnetic entropy change and a small hysteresis in the isothermal magnetic field-dependent magnetization measurements. After annealing, the phase transition temperature decreases slightly and the magnetization is sharply decreasing at Curie temperature. The sharp change of magnetization at phase transition temperature is accompanied by a significant increase in the magnetic entropy change, i.e., magnetic entropy change value for the magnetic field change of 1 T was increased from −3.3 to −6.3 J kg−1 K−1. Moreover, after annealing, hysteresis losses reduced significantly for ∆H = 7 T. Accordingly, the heat treatment has a significant effect on magnetocaloric properties of the CoMn0.95Ti0.05Ge alloy.

Effect of proportion change of aluminum and silicon on magnetic entropy change and magnetic properties in La0.8Ce0.2Fe11.5Al1.5-xSix compounds

The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La0.8Ce0.2Fe11.5Al1.5–xSix (x=0.4, 0.5, 0.6, 0.7) compounds were studied by X-ray diffraction (XRD) and a superconducting quantum interference device magnetometer (SQUID). The results showed that all the compounds presented cubic NaZn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La0.8Ce0.2Fe11.5Al1.1Si0.4, La0.8Ce0.2Fe11.5Al1.0Si0.5, La0.8Ce0.2Fe11.5Al0.9Si0.6 and La0.8Ce0.2Fe11.5Al0.8Si0.7 were found to be –9.6, –4.8, –5.8 and –11.7 J/(kg·K), respectively. Moreover, their hysteresis losses were 1.13 J/(kg·K) or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.

Structure and magnetic properties of Co2(Cr1−xFex)Al, (0 ≤ x ≤ 1) Heusler alloys prepared by mechanical alloying

In the present study, a series of nanocrystalline Co2(Cr1−xFex)Al Heusler alloy powders were successfully prepared by high energy ball milling and the effect of substitution of Fe for Cr on the microstructure and magnetic properties was investigated in detail. The Co2CrAl alloy powder consisted of only A2 type disordered structure whereas the substitution of Cr by Fe led to the appearance of increasing amounts of B2 type disordered structure along with A2 type structure. All the Co2(Cr1−xFex)Al Heusler alloy powders demonstrated high spontaneous magnetization together with a very small hysteresis losses. The saturation magnetization, remanence, coercivity, and Curie temperature increased with increasing Fe content. The increasing magnetization with increasing Fe content was attributed to the replacement of antiferromagnetic Cr by strongly ferromagnetic Fe and an increasing amounts of relatively more ordered, atomically as well as ferromagnetically, B2 structure as compared to that of A2 phase. The increment in remanence and coercivity with increasing Fe content were associated with the variation in microstructural characteristics, such as grain size, lattice defects, and the presence of small amounts of magnetic/nonmagnetic secondary phases. The increment in Curie temperature with increasing Fe content was attributed to the enhancement of d-d exchange interaction due to the possible occupancy of vacant sites by Fe atoms. All the Heusler alloys indicated extremely low magnetic anisotropy and the relative anisotropy decreased with increasing Fe content.

Fast and Controllable Electric‐Field‐Assisted Reactive Deposited Stable and Annealing‐Free Perovskite toward Applicable High‐Performance Solar Cells

Recently, organic–inorganic hybrid perovskite materials have drawn great attention for their outstanding performance in high‐efficiency solar cells. Successful synthesis has been realized either in solution‐based chemical deposition or vapor deposition. However, conflicts have never ceased among quality control, growth rate, process complexity, and instrument requirement, which have limited their development toward real applications. In this work, the first electrochemical fabrication of perovskite toward high‐efficiency and scalable perovskite solar cells (PSCs) is established. The morphology and crystallization of the CH3NH3PbI3 film can be effectively controlled by simply modulating a few physical parameters. A detailed study on its optoelectronic properties reveals significantly improved film quality and interfacial conditions. Aided by this, the total process does not require standard annealing, which greatly reduces the total growth time from hours to minutes. Up to now, an efficiency of 15.65% has been achieved in planar PSCs under 1 sun AM 1.5 condition, with small hysteresis and efficiency loss under longtime exposure to air. Moreover, high efficiency (10.45%) can be easily attained for large cells (2 cm2). This result will hopefully facilitate research for applicable high‐efficiency PSCs and other multicomponent materials as well.

Large reversible magnetocaloric effect in a Ni-Co-Mn-In magnetic shape memory alloy

Reversibility of the magnetocaloric effect in materials with first-order magnetostructural transformation is of vital significance for practical magnetic refrigeration applications. Here, we report a large reversible magnetocaloric effect in a Ni49.8Co1.2Mn33.5In15.5 magnetic shape memory alloy. A large reversible magnetic entropy change of 14.6 J/(kg K) and a broad operating temperature window of 18 K under 5 T were simultaneously achieved, correlated with the low thermal hysteresis (∼8 K) and large magnetic-field-induced shift of transformation temperatures (4.9 K/T) that lead to a narrow magnetic hysteresis (1.1 T) and small average magnetic hysteresis loss (48.4 J/kg under 5 T) as well. Furthermore, a large reversible effective refrigeration capacity (76.6 J/kg under 5 T) was obtained, as a result of the large reversible magnetic entropy change, broad operating temperature window, and small magnetic hysteresis loss. The large reversible magnetic entropy change and large reversible effective refrigeration capacity are important for improving the magnetocaloric performance, and the small magnetic hysteresis loss is beneficial to reducing energy dissipation during magnetic field cycle in potential applications.

Influence of partial substitution of cerium for lanthanum on magnetocaloric properties of La1–xCexFe11.44Si1.56 and their hydrides

The structure and magnetocaloric properties of La1–xCexFe11.44Si1.56 and their hydrides La1–xCexFe11.44Si1.56Hy (x=0, 0.1, 0.2, 0.3, 0.4) were investigated. The samples crystallized mainly in the cubic NaZn13-type structure with a small amount of α-Fe phase as impurity. The lattice constants and Curie temperature presented the same change tendency with increasing of Ce content. For the hydrides, the influence of Ce content on lattice constants was weakened and the values of H concentration y were approximate to be 1.56. The La1–xCexFe11.44Si1.56 compounds exhibited large values of isothermal entropy change –ΔSm around the Curie temperature TC under a low magnetic field change of 1.5 T. The value of –ΔSm increased and then decreased with increasing Ce content, reached the maximum, 26.07 J/kg·K for x=0.3. TC increased up to the vicinity of room temperature by hydrogen absorption for the Ce substituted compounds, but TC only slightly decreased with increasing Ce content. The first-order metamagnetic transition was still kept in the hydrides and the maximum values of –ΔSm were lower than those of the La1–xCexFe11.44Si1.56 compounds, but still remained large values, about 10.5 J/kgK under a magnetic field change of 1.5 T. The values of –ΔSm were nearly independent of the Ce content and did not increase with increasing x for the hydrides. The La1–xCexFe11.44Si1.56Hy(x=0–0.4) hydrides exhibited large magnetic entropy changes, small hysteresis loss and effective refrigerant capacity covered the room temperature range from 305 to 317 K. These hydrides are very useful for the magnetic refrigeration applications near room temperature under low magnetic field change.

A coupling of martensitic and metamagnetic transitions with collective magneto-volume and table-like magnetocaloric effects

A coupling of the first-order paramagnetic-to-induced-ferromagnetic martensitic and the second-order antiferromagnetic-to-ferromagnetic metamagnetic transitions was found in MnNi0.8Fe0.2Ge alloy. Based on the coupling, a magneto-volume effect driven by the martensitic transition and a table-like magnetocaloric effect generated by the successive magnetic phase transitions arise collectively. By using the magneto-volume effect, the internal stress in the volume-expansion martensitic transition was determined at 350 MPa. The magnetocaloric effect, with a wide working temperature range of 26 K around room temperature, shows a small hysteresis loss (5 J kg−1) and a large net refrigerant capacity (157 J kg−1).

Realization of small intrinsic hysteresis with large magnetic entropy change in La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 by controlling itinerant-electron characteristics

Tuning of phase-transition characteristics in La(FexSi1−x)13 was conducted in view of the correlation between microscopic itinerant electron natures and macroscopic thermodynamic (magnetocaloric) quantities. To realize a small hysteresis loss QH accompanied by a large magnetic entropy change ΔSM in La(FexSi1−x)13, two types of modulation based on itinerant electron characteristics, namely, the Fermi-level shift and the magnetovolume effect were combined by complex partial substitution of Al and Pr. Ab-initio calculations predict the reduction of a transition hysteresis owing to the Fermi-level shift after partial substitution of Al. On the other hand, the chemical pressure arisen from partial substitution of Pr enhances ΔSM through magnetovolume effect. The selective enhancement of ΔSM apart from QH by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ΔSM of La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 is −18 J/kg K under a magnetic field change of 0–1.2 T, while the maximum value of QH becomes 1/6 of that for La(Fe0.88Si0.12)13.

Magnetocaloric effect in La0.5Pr0.5Fe11.5Si1.5 compounds with a combined addition of Co and C

The influence of a combined addition of Co and C on the magnetocaloric effect in the La0.5Pr0.5Fe11.5Si1.5 compound is investigated. The addition of Co and C can adjust Curie temperature (TC) to around room temperature. Although the magnetic entropy change (ΔSM) of La0.5Pr0.5Fe11.5−xCoxSi1.5C0.2 decreases with the increase of x, the maximum hysteresis loss at TC reduces remarkably from 23.6 J/kg for x = 0 to close to zero for x = 0.2. For x = 0.8, the maximum value of ΔSM is −11.6 J/kg K with an RC value of 386 J/kg around TC = 295 K for a magnetic field change of 0-5 T. Our result reveals that a large ΔSM and a small hysteresis loss can be simultaneously achieved in NaZn13-type LaPrFeSi compounds with a combined addition of Co and C.

MAGNETIC PROPERTIES Cu DOPED ZnO:Fe SEMICONDUCTORS

Magnetization measurements were performed on a series of Zn 0.9-x Fe 0.1 Cu x O samples (0 ≤ x ≤ 0.10). Small hysteresis losses are seen at low temperatures. The ferromagnetic exchange interaction has been evaluated from the inverse DC magnetic susceptibility versus T and the molecular field theory. We found that Cu -doping greatly enhances the FM exchange interaction, increases the saturation magnetization, hysteresis losses and the magnetic susceptibility. Arrott-Kouvel plot has been used to study the spontaneous magnetic moment at low temperatures. We show that hysteresis losses cannot be taken as the only evidence for the appearance of the ferromagnetic order in these semiconducting semi-magnetic materials.

Giant magnetic entropy change in colossal magnetoresistance in La0.7Ca0.3MnO3 material in low field

The structural, magnetic, and magnetocaloric properties of the manganite La0.7Ca0.3MnO3 have been studied. Change in the giant magnetic entropy was observed without any noticeable magnetic hysteresis but with small thermal hysteresis losses. We observed a first order magnetic phase transition around 251 K. The magnetic entropy change observed in this work is estimated to be 5.27 J/kg K for field changes from 0 to 1.5 T based on magnetization measurements. This value is about twice as large as those for other perovskite manganites and is even larger than for Gd-based magnetic materials at low fields. In addition, the entropy change was estimated by using the heat capacity method, which can be well explained by the Maxwell relation.