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Post-sinter annealing process plays an important role in the microstructures and magnetic properties of the Nd-Fe-B sintered magnets. In this paper, systematically investigated are the magnetic properties and microstructures of the as-sintered and post-sinter annealed Nd-Fe-B magnets with Pr-Fe-Ga boundary addition. Two choice consecutive annealing methods are adopted at high and low temperatures, namely the 1st annealing at 880 oC for 2 h and then the 2nd annealing at 440 oC for 3 h. It is exceptional to find out that both the remanence and coercivity are improved after 2nd annealing process for this type of magnet. The coercivity is hugely increased from 10.09 kOe for the as-sintered sample to 17.19 kOe for the 2nd annealed magnet, with a significant increment of 70.37% in coercivity. The extraordinary magnetic properties of Br=14.44 kGs, Hcj=17.19 kOe and (BH)max=51.08 MGOe are obtained for the designated Nd-Fe-B sintered magnets without heavy rare earth (HRE) elements manufactured by dual alloy method. The Curie temperature is monotonically decreased from 634 K to 602 K while the c-axis alignment degree is optimized after annealing. Microstructural observation and analysis indicate that the elemental distribution patterns are altered after the 2nd annealing. The diffusion of the aggregate (Pr,Nd,Cu,Ga)-rich phase from triple junctions into the grain boundary regions is ascribed to the formation of thin and continuous grain boundary layer, which is critical to improve the microstructures and magnetic properties.

SmCo5 magnets were prepared by spark plasma sintering (SPS) technique. The phase constitutions, magnetic properties, and microstructures of magnets prepared under different sintering temperatures were investigated systematically. It is observed that the 1:5 phase and 2:7 phase coexist in the magnet, and 2:17 phase appears when the temperature rises to 1050 °C. The best magnetic properties were obtained for the magnets prepared at 1000 °C, with remanence Jr = 0.45 T, intrinsic coercivity Hcj = 985 kA/m, and maximum energy density (BH)max = 37 kJ/m3. It is shown that the SPSed magnet prepared at 1000 °C exhibits excellent thermal stability which is described in terms of temperature coefficient of remanence (α) = −0.15%/°C and temperature coefficient of coercivity (β) = −0.25%/°C in the temperature range of 27–400 °C. The microstructure analysis showed that the high density of the magnet and the uniform distribution of the hard magnetic phase are the main reasons for the excellent magnetic properties.

NdFeB hot-pressed and hot-deformed magnets were prepared by hot-pressed (HP) sintering and spark plasma sintering (SPS). The effects of sintering mechanisms of SPS and HP on the microstructure of hot deformation magnets were studied. The temperature of the mold surface is much higher than that of the sample in the cavity in HP, but lower than that of the sample in SPS. The Nd-rich phase is uniformly distributed and the grain size is smaller in the hot-deformed magnets prepared by HP, while the Nd-rich phase is excessively enriched and the grain size in the liquid-enriched region is abnormal in the hot-deformed magnets prepared by SPS. The comprehensive magnetic properties of hot deformed magnets prepared by SPS are significantly lower than those prepared by HP.

The magnetic properties, magnetocaloric effect and magnetoresistance in ErNi single crystal have been investigated in detail. With decreasing temperature, ErNi single crystal undergoes two successive magnetic transitions: a paramagnetic to ferromagnetic transition at TC =11 K and a spin-reorientation transition at TSR = 5 K. Meanwhile, a sharp field-induced metamagnetic transition is observed below the TC along the a axis. ErNi single crystal possesses a giant magnetocaloric effect around TC. The maximum magnetic entropy change is -36.1 J (kg K)−1 along the a axis under the field change of 0−50 kOe. In particular, the rotating magnetocaloric effect in ErNi single crystal reaches its maximum under a relatively low field, and the maximum rotating entropy change with a value of 9.3 J (kg K)−1 is obtained by rotating the applied field from the [011] to [100] directions under 13 kOe. These results suggest that ErNi could be a promising candidate for magnetic refrigeration working at liquid-helium temperature region. Moreover, a complicated transport behavior is uncovered in ErNi single crystal, which is attributed to the complex magnetic states and magnetic polaronic effect. Both positive and negative magnetoresistance are observed. A considerable large magnetoresistance with the value of -34.5 % is acquired at 8 K under 50 kOe when the field is along the [100] direction.

Cerium doped zinc oxide/carbon nanotubes (Ce doped ZnO/CNTs) composites are synthesized using sol-gel, hydrothermal deposition and one-pot hydrothermal methods. These composites are tested for photocatalytic hydrogen evolution from water-methanol mixture to check the effect of synthesis method on photocatalytic activity of these composites. Each synthesis method induces unique physiochemical properties in composite and hydrogen evolution rates. The composite prepared by one-pot hydrothermal method shows highest hydrogen evolution of 759 μmolh−1g−1 under sunlight. This hydrogen evolution rate is significantly higher than the sol-gel synthesized photocatalyst (579 μmolh−1g−1) and hydrothermal deposition method (621 μmolh−1g−1). The high hydrogen evolution activity of the prepared composites can be attributed to small crystallite size, low recombination of charge carriers, large active surface area, short diffusion pathway for photoinduced electrons and high oxidation potential of photogenerated holes. Focused on different methods, this study provides a pathway for production of efficient semiconductor photocatalysts for environmental applications.

In this study, the liquid phase plasma (LPP) was irradiated over pure zinc oxide (ZnO), strontium (Sn) doped ZnO, and Sn doped ZnO/CNTs photocatalysts for hydrogen evolution from pure water and from aqueous solution of water-methanol. The possible relationship between hydrogen evolution and optical emissions from LPP for activation of ZnO based photocatalysts was revealed. The role of carbon nanotubes (CNTs) as a support material for improved photocatalytic hydrogen evolution was also investigated in this study. The photocatalytic hydrogen evolution from water mixed methanol under LPP irradiation was compared with pure water splitting. The photolysis produced negligible amount of hydrogen due to minimal photodecomposition of water molecules under LPP irradiation. The plasma born reactive species also played crucial role in photolysis. However, the hydrogen evolution rate increased significantly in the presence of ZnO photocatalyst. Further improvement in hydrogen evolution rate was noticed on Sn doping of ZnO and compositing with CNTs. The highest hydrogen evolution rate of 11.46 mmh−1g−1 from water mixed methanol was achieved with Sn doped ZnO/CNTs photocatalyst. This hydrogen evolution rate from water-methanol solution was 9 times higher than from the splitting of pure water. This hydrogen evolution rate is attributed to excessive production of hydroxyl radicals, red shift in optical band gap of Sn doped ZnO/CNTs photocatalyst, slow electron-hole recombination and fast decomposition of methanol as sacrificial reagent.

In order to obtain high magnetic properties in Ce–Pr–Nd–Fe–B spark plasma sintered (SPSed) magnets, the alloys were introduced by the dual-alloy method. The relationship of microstructure, magnetic properties, and thermal stability was investigated. The remanent magnetization, coercivity, and maximum energy product were sharply enhanced from 0.68 T, 653 kA/m, and 75.62 kJ/m3 to 0.80 T, 865 kA/m, and 104 kJ/m3 for the magnets that with 0 and 75 wt.% Pr–Fe–B addition. The Curie temperature also increased from 542 K to 563 K after adding Pr–Fe–B alloys. The scanning electron microscopy (SEM) analysis showed that, during the sintering process, the rare-earth elements migrated into the flake boundary and diffused in 2:14:1 main phases; thus, (Ce, Pr, Nd)2Fe14B hard magnetic phases were formed, which is helpful to optimize the microstructure and magnetic properties. An enhancement of exchange coupling among the grains of SPSed magnets was obtained as a result of grain refinement by adding Pr–Fe–B alloys.

Nowadays, searching for the materials with multiple magneto-functional properties and good mechanical properties is vital in various fields, such as solid-state refrigeration, magnetic actuators, magnetic sensors and intelligent/smart devices. In this work, the magnetic-field-induced metamagnetic reverse martensitic transformation (MFIRMT) from paramagnetic martensite to ferromagnetic austenite with multiple magneto-responsive effects is realized in Fe-doped Co-V-Ga Heusler alloys by manipulating the magnetic ordering. The martensitic transformation temperature Tm reduces quasi-linearly with increasing Fe-content. In strikingly contrast with the Fe-free alloys, the magnetization difference (ΔM') across martensitic transformation increases by three orders of magnitude for Fe-doped alloys. The increased ΔM' should be ascribed to the reduction of Tm, almost unchanged Curie temperature of austenite and the increased magnetic moment in the samples with higher Fe-content. The large ΔM' provides strong driving force to realize the MFIRMT and accordingly multiple magneto-responsive effects, such as magnetocaloric, magnetoresistance and magnetostriction effects. Meanwhile, giant Vickers hardness of 518 HV and compressive strength of 1423 MPa are achieved. Multiple magneto-responsive effects with exceptional mechanical properties make these alloys great potential candidates for applications in many fields.

Recently it is a hot topic to make full use of high abundant Y element in Nd2Fe14B-type permanent magnets. In contrast to Pr and Nd elements, Y shows different metallurgical behaviors during preparation process. In this paper, we have explored the magnetic properties, microstructures and corrosion performance of Pr-Nd-Y-Fe-B magnets fabricated by spark plasma sintering (SPS) technique from the ribbons of nanocrystalline and amorphous precursors, respectively. The coercivity and maximum energy product were improved for the magnets prepared from amorphous precursor materials (denoted as SPS-A hereafter) compared with the magnets prepared from crystalline precursor materials (denoted as SPS-C hereafter). Magnetic properties of Jr = 0.79 T, Hci = 864 kA/m, and (BH)max = 102 kJ/m3 were obtained for SPS-A magnets. In contrast with SPS-C magnets, the magnetic properties of SPS-A magnets are not so sensitive to the preparation conditions, which is quite beneficial to the homogeneity of microstructure and enhancement of coercivity for large-scale production of the designated magnets. Aggregated (Pr,Nd,Y)-rich phase was found out in SPS-C magnets. Pr and Nd elements are rich at grain boundary while Y is distributed uniformly at main phase and grain boundary phase. The strip grains and equiaxed grains exist in SPS-C and SPS-A magnets, respectively. The enhanced magnetic properties for SPS-A magnets are accredited to the uniform distribution of rare-earth-rich phase and low demagnetization factor. It is revealed by electrochemical test and dipping test that the corrosion potential is more positive and the corrosion rate is slower for the SPS-A magnets in 3.5 wt.% NaCl solution. The work is also expected to shed light on developing the nanocrystalline Pr-Nd-Y-Fe-B SPSed high-performance magnets in industry.

In the present work, we reveal a novel finding, that is, self-assembled grain boundary precipitates for realizing the magnetic-field-induced metamagnetic transition by employing low melting point metal in materials. This strategy has been experimentally verified in a well-established ferrimagnetic compound Mn2Sb by doping the bismuth (Bi) element with a low melting point of just 271.3°C. Bi solidifies later than the Mn2(Sb,Bi) main phase in (Mn2Sb)1-xBix system (the melting point of ~948°C for Mn2Sb), and aggregates spontaneously along the grain boundaries, forming Bi-rich grain boundary precipitates to coat main phase grains. This is very similar to the Nd-rich grain boundary phase in Nd-Fe-B permanent magnets. The fraction of Bi-rich grain boundary phase can be controlled by Bi-content. As a result, the magnetic field induced steep magnetoelastic transition from antiferromagnetic to ferrimagnetic is achieved in (Mn2Sb)0.89Bi0.11 alloy with giant multiple functional properties in Bi-doped Mn2Sb. Especially, the magnetic entropy change maximum nearly quadruples when Bi-doping increases from 0.03 to 0.11. Giant negative magnetoresistance of more than 65% under μ0∆H = 0–5 T, and magnetostrain of ~1802 ppm under μ0H = 8.5 T are obtained in (Mn2Sb)0.89Bi0.11. It should pave a way to achieve the magnetic transition and enhance the magnetoresponsive effects in designing similar coherent materials by employing low melting point metal doping to form the dual-phase heterogeneous structure.

The purpose of this paper is to study the influence of Mo addition on the phase morphologies, microstructures and magnetic properties of the designated alloys. It is found out that the coercivity Hcj increases unevenly from 12.2 kOe for (Nd0.8Ce0.2)13Fe82B5 to the maximum value of 13.3 kOe for (Nd0.8Ce0.2)13Fe80B5Mo2. The transmission electron microscopy images demonstrate that the grain size decreases with the addition of Mo, which indicates that Mo has grain refinement effect. The correlative analysis gives rise to the conclusion that the coercivity mechanism of the investigated alloys is dominated by pinning type. All in all, the enhancement of the magnetic properties is mainly attributed to the synergistic impact of grain refinement, pinning effects and the microstructural homogenization. The research may shed light on the potential development and application of rare earth-based counterpart magnets.

The magnetic properties of alnico alloys are highly dependent on the spinodally decomposed nanostructure. In this article, we report the fabrication of alnico nanoribbons and the effects of various heat treatments on the magnetic properties, spinodal decomposition, microstructure, and temperature stability. It is found that the spinodal decomposition occurs in a wider range of temperatures from 800 °C to 860 °C. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses of the microstructure confirmed that the nanostructure phases develop in a wide temperature range. Aspect ratio of the order of ~20 is obtained by optimizing the heat treatment conditions. Magnetic properties of H cj = 815 Oe, B r = 6.70 kG, and (BH) max = 1.88 MGOe are obtained after simplified heat treatment. The magnetic properties of the alloys are measured at low (10 K) and at high (800 K) temperature, and it is shown by calculating temperature coefficient of remanence (α) and temperature coefficient of coercivity (β) that alnico ribbons possess extraordinary temperature stability at low and high temperatures.

The effects of Ta doping on the magnetic properties, temperature stabilities, phase constituents, intergranular exchange interactions, and microstructures of (Nd0.8Ce0.2)13.5Fe80.5−xTaxB6 (x = 0–1.5) nanoribbons are investigated in this paper. It is found that Ta doping increased the coercivity of the alloys, while the remanence remained nearly unchanged. The temperature stability of the alloys improved significantly as the absolute value of temperature coefficient of coercivity β enhanced from 0.48%/K for Ta-free alloy to 0.38%/K for the alloys with 0.3–1.5 at.% Ta addition. The lattice constants (a, c), unit cell volume, and phase transition temperatures (Tsr, TC) of the alloys changed by adding Ta into the alloys. Comprehensive best magnetic properties of Hcj = 16.0 kOe, Br = 7.65 kG, and (BH)max = 12.60 MGOe are obtained in (Nd0.8Ce0.2)13.5Fe79.6Ta0.9B6 ribbon. The improvement in magnetic properties is mainly attributed to refined and uniform microstructure of the Ta-doped alloys.

The formation of the paramagnetic CeFe2 phase has deleterious effects on the magnetic properties of Ce Fe B type alloys. In order to reduce the volume fraction of the CeFe2 phase and improve the magnetic properties of cost efficient Ce Fe B magnetic alloys, Ce17Fe77-xGexB6 (x = 0.0–1.5) alloys were fabricated by melt spinning technique. The crystal structures, magnetic properties, intergranular exchange interactions and phase transition temperatures of CeFe2 and Ce2Fe14B phases were investigated. The critical amount of Ge doping enhanced the magnetic properties of the alloys by partially decreasing the formation of paramagnetic CeFe2 phase and refining the nano-grains. The optimized magnetic properties of coercivity Hcj = 467 kA/m, remanence Br = 0.51 T and energy density (BH)max = 40.6 kJ/m3 were obtained for Ce17Fe76.4Ge0.6B6 alloy. The analysis of Henkel plots confirmed that the exchange interaction among nano-grains was greatly improved for the optimized doping of Ge. The improved magnetic properties of the investigated alloys are attributed to the refined grains, enhanced intergranular exchange interactions and the decrease of paramagnetic phase for the critical amount of Ge.

Nanocrystalline Ce–Fe–B based rare earth permanent magnets are prepared by spark plasma sintering (SPS) method using grounded ribbons as raw material. The phase compositions, microstructure, magnetic properties, intergranular magnetic interactions, recoil loops, and corrosion resistance of the magnets are investigated systemically. The relationship among sintering processes, microstructures, and magnetic characteristics are discussed in depth by mainly using transmission electron microscope (TEM) and Physical Property Measurement System (PPMS) techniques. It is demonstrated that the sintering temperature has a significant influence on the average grain size and width of coarse grain areas. The optimized magnetic properties of remanent magnetization $J_{r}= 0.37$ T, coercivity $H_{\mathrm {ci}} = 227$ kA/m, and maximum energy product $(BH)_{\mathrm {max}}= 16$ kJ/m3 are obtained at 650 °C under 50 MPa for 2 min. Their exchanging coupling interactions are quite weak compared with those of the counterpart alloys. The exchanged decoupled of soft magnetic materials and inhomogeneous magnetic anisotropy result in open and steep recoil loops. The electrochemical experiment results display that the corrosion resistance of the magnets is improved by sintering at high temperature. This paper plays a role in guiding the future research and development of nanocrystalline Ce–Fe–B based permanent magnetic materials.

FeSiCr nanoparticles were fabricated by plasma arc-discharging method. The particle size is controlled by regulating the ratio of Ar and H 2 . The proper particle size improves the microwave attenuation capability and optimizes the impedance matching of the FeSiCr nanoparticles. When the ratio of Ar:H 2 = 80:20, the calculated reflectivity of the FeSiCr nanoparticle reaches −50.7 dB at 17.3 GHz ( d = 1.5 mm). By regulating the proportion of heat source gas H 2 and changing the coating thickness from 1.0 to 4.0 mm, the effective absorbing bandwidth ( 2 is a feasible way to control the nanoparticle size.

The magnetic properties, thermal stabilities and microstructures of misch-metal (MM) alloys with nominal composition of MM2.0+xFe14B (x = 0–0.6) prepared using melt-spun technique are investigated. The XRD pattern showed that the ribbons consist of the MM2Fe14B main phase, α-Fe, Fe3B and ReFe7 phases. The coercivity of all ribbons enhances with increasing the content of MM, while the remanence gradually decreases. Interestingly, there is an increase in remanence of MM2.2Fe14B ribbon, which is attributed to the strong intergranular exchange coupling effect. The Curie temperature of all the ribbons is around 546 K, which does not change with the content of MM. By the EDS analysis, we have clarified that the changes of the temperature stability are mainly related to the distribution of rare earth content in the main phase. This study shows that the magnetic properties of the alloys can be improved by optimizing the content of rare earth elements. The ribbons in the optimum condition exhibit a coercivity of 899 kA/m and a (BH)max of 116 kJ/m3, which can be used to produce high cost performance MM-Fe-B magnets.

The all-d-metal Ni50-xCoxMn35Ti15 (x = 13,13.5) ferromagnetic shape memory alloy ribbons are successfully fabricated. The intermartensitic transformation and martensitic transformation arrest phenomenon are systematically investigated. In contrast to melt-spun ribbons, the annealed ribbons reveal an intermartensitic transformation from five-fold (5 M) modulated to non-modulated (L10) martensite below B2→5 M martensitic transformation. The XRD, TEM, DSC and temperature dependence of electrical resistivity measurements validate the occurrence of intermartensitic transformation. On the other hand, the magnetic-field-induced martensitic transformation arrest is achieved in these all-d-metal ribbons like other normal Ni-Mn-based Heusler alloys consisting of p-group and d-group elements. Strikingly, a kinetic de-arrest phenomenon is brought about in all-d-metal ribbons with the increasing heat treatment temperatures. The associated origins are discussed in these ribbons, which is very significant for deeply understanding the arrest and de-arrest phenomenon in ferromagnetic shape memory alloys. What's important, excellent magneto-functional and mechanical properties are obtained in these ribbons. Ni36.5Co13.5Mn35Ti15 annealed ribbon displays the best integrated properties, such as large magnetoresistance (∼34.9%), magnetic entropy change peak value (∼24.9 Jkg−1K−1) and effective refrigerant capacity (∼122.5 Jkg−1) under the field change of Δμ0H = 0–5 T, and large Vickers hardness [2.75 GPa (280.7HV)]. These make the all-d-metal Ni-Mn-based Heusler alloy ribbons attractive in the practical applications.

The carbon coated core-shell C@Fe3C/Fe nanocomposites were prepared by plasma arc-discharging method. The core-shell and graphite network structures were obtained, which could improve the absorbing properties by optimizing the impedance matching and increase the internal reflections of the propagated microwave. By varying the coating thickness from 1.0 to 5.0 mm, the reflectivity of C@Fe3C/Fe nanocomposites prepared in 30% CH4 is less than −20 dB nearly in the whole range of 2–18 GHz. The minimum reflection loss value reaches −32.9 dB at 14.2 GHz and the effective bandwidth (

Ce-Fe-B spark plasma sintered (SPSed) magnets prepared with different ratio of alloys of Ce-Fe-B and Pr-Nd-Fe-B by dual alloy method are investigated in this paper. As expected, the remanent magnetization Jr, coercivity Hci and maximum energy product (BH)max of SPSed magnets increase obviously with increasing weight percentage of Pr-Nd-Fe-B alloy. The magnetic properties of Jr = 0.71 T, Hci = 915 kA/m, (BH)max = 72 kJ/m3 are obtained for the SPSed magnets with 80 wt% Pr-Nd-Fe-B alloy. There are three Curie temperatures in this type magnet, which implies the coexistence of three hard magnetic phases. The second Curie temperature depends on the Pr-Nd-Fe-B content. With increasing Pr-Nd-Fe-B alloy content, the volume fraction and width of coarse grain zone decrease. It is shown by the microstructure analysis that the rare earth elements diffuse during sintering process resulting in the formation of Pr-Nd-Ce-Fe-B hard magnetic phase. The intergranular exchange coupling strength is enhanced with increasing Pr-Nd-Fe-B content. The present research may be a potential reference for further research and development of this type Ce-containing nanocrystalline permanent magnetic materials.

In this paper Hf doped (Nd0.8Ce0.2)13Fe82−xB5Hfx (x = 0, 0.5, 1.0, 2.0, 3.0) ribbons were fabricated by melt-spinning technique, and their microstructure, magnetic properties and coercivity mechanism have been investigated methodically. It is found that the coercivity of (Nd0.8Ce0.2)13Fe82−xB5Hfx ribbons is enhanced for 0 ≤ x ≤ 2.0 at.% while the remanence decreases slightly. The optimal comprehensive magnetic properties Jr = 7.5 kG, Hcj = 12.7 kOe, and (BH)max = 12.3 MGOe, are obtained at x = 1.0 at.%. The grain size decreased with the addition of Hf and more uniform microstructure evolved. The coercivity mechanism of the (Nd0.8Ce0.2)13Fe82−xB5Hfx (x = 0–3.0) ribbons is found to be the pinning mechanism based on the systematic investigations and analysis. The synchronization of the grain refinement and the pinning effect lead to the improvement of magnetic properties.

Ce-Fe-B-based rare earth permanent magnets are prepared by spark plasma sintering (SPS) technique, and low melting NdCu alloy is added to improve its magnetic properties and thermal stabilities. The X-ray diffraction (XRD) result indicates that the lattice constants of the unit cell of 2:14:1 phase increase with NdCu addition. The remanent magnetization, coercivity and maximum energy product are enhanced remarkably from 0.37 T, 227 kA/m, 16 kJ/m3 for the sintered magnets without NdCu addition to 0.47 T, 476 kA/m, 30 kJ/m3 for those with 20 wt% NdCu addition. The temperature coefficients of remanence (α) and coercivity (β) of the spark plasma sintered magnets (denoted as SPSed magnets thereafter) are improved from −0.46%/K, −0.60%/K to −0.34%/K, −0.55%/K in the range of 300–400 K. There are two Curie temperatures in the Ce-based magnets with NdCu addition, which implies the coexistence of two hard magnetic phases. The second Curie temperature depends on the NdCu content. It is shown by the microstructure analysis that a typical core-shell structure is formed with Ce-rich core and Ce-lean shell by NdCu addition. Furthermore, it is displayed that Nd atoms prefer to diffuse into the Ce-lean flakes. The Nd-Ce exchange mechanism and immigration behavior of elements are finally investigated. The intergranular exchange coupling strength is enhanced in NdCu-added magnet. It is found out that the core-shell structure plays an important role in the special microstructure evolution and the enhancement of the magnetic properties for the typical Ce-Fe-B-based SPSed magnets by NdCu addition.

An argon plasma jet was sustained in open air and characterized for its chemical composition. The optically characterized plasma jet was used to treat industrial wastewater containing mixed textile dyes and heavy metals. Since plasma jet produces UV-radiations, the photocatalytic TiO2 was used to enhance plasma treatment efficiency especially for degradation of dyes. Mixed anatase and rutile phases of TiO2 (5.2–8.5 nm) were produced through surfactant assisted sol–gel approach. The emission spectrum confirmed the presence of excited argon, OH, excited nitrogen, excited oxygen, ozone and nitric oxide in the plasma jet. The spectral lines of excited Ar, NO, O3, OH−, N2, $${\mathrm{N}}_{2}^{+}$$ N 2 + , O, $${\mathrm{O}}_{2}^{+}$$ O 2 + and O+ species were observed at wavelength of 695–740 nm, 254.3 nm, 307.9 nm, 302–310 nm, 330–380 nm, 390–415 nm, 715.6 nm, 500–600 nm and 400–500 nm. These reactive species decompose the organic pollutants and separate the heavy metals from the water samples. The conductivity of plasma exposed water samples increased while pH and hardness decreased. The atomic absorption spectrophotometry analysis confirmed the presence of heavy metals in the samples, which were effectively removed through plasma treatment. Finally, the effect of plasma treatment on Staphylococcus aureus strains was more pronounced than Escherichia coli strains.

There is a close relationship between the magnetic properties of alnico permanent magnetic alloys and the nano-scaled spinodally decomposed structure which results from various heat treatment cycles. In this paper, different heat treatment cycles are employed to cast alnico 8 alloys with composition 32.3Fe-37.5Co-13.7Ni-6.2Al-5.8Ti-3.4Cu-0.2Zr-0.1S-0.8Nb. It is observed that magnetic field treatment at high temperature for specific time is the most effective method to obtain better microstructure and magnetic properties. The mosaic structures consisting of Fe-Co phase and Al-Ni rich phase are best separated during thermomagnetic treatment for 4–5 min and refined during low temperature treatments. The bias growth of the ferromagnetic phase does not develop in absence of magnetic field, and hence the phases are not refined and separated completely. This produces isotropic alnico alloys with low magnetic properties. However, continuous cooling of the alloys in magnetic field followed by isothermal treatment without magnetic field provides moderate magnetic properties. Treatment at high temperatures in field and without field for longer time leads to the coarsening of spinodal phases and poor magnetic properties. The optimum magnetic properties of Hcj = 1.7 kOe, Br = 8.0 kGs and (BH)max = 5.02 MGOe are attributed to the refined microstructure of the thermomagnetically treated alloys.

The purpose of this paper is to explore Dy-free Nd-Fe-B magnetic alloys which could be developed into Dy-free permanent magnets operating at high temperatures. Nd13.5Fe80.5-xB6Tax (x = 0.0–1.2) alloys have been fabricated by melt spinning technique. It is found out that the addition of Ta in Nd-Fe-B alloys improves the extrinsic and microstructural properties resulting in better magnetic properties and thermal stability. The thermal stability of the alloys measured in terms of temperature coefficient of coercivity (β) improved from −0.41%/K for Nd13.5Fe80.5B6 to −0.27%/K for Nd13.5Fe79.9B6Ta0.6 in the temperature range 300–400 K. It is demonstrated that Ta acts as refractory element, which refines grains and reduces the volume fraction of the undesirable non-magnetic phases. As a result the magnetic properties (Br, Hcj and (BH)max) of the alloys are enhanced, however the intrinsic properties (Tc, Tsr) remain unchanged. The domain wall pinning, determined to be the dominant coercivity mechanism in the investigated alloys, also strengthened by the addition of Ta. It is concluded that Ta alloying can improve the microstructures, magnetic properties and thermal stability of the designated alloys. This research may shed light on further research and development of Dy-free high temperature resistant rare earth magnets.

A balanced consumption of the rare earth resources can be realized by increasing the content of Ce in Nd-Fe-B magnetic alloys. However, the substitution of Ce for Nd reduces the magnetic properties and the Curie temperature of the 2:14:1 phase resulting in limited application fields. In this manuscript, targeting to increase the Curie temperature by maintaining the magnetic properties at acceptably high level, Fe in 25% Ce substituted Nd-Ce-Fe-B alloys has been substituted by Alnico constituent elements. The Curie temperature of the main phase for 25% Ce substitution (544 K) is enhanced to 589 K by 20% Alnico substitution which is higher than the Curie temperature of the pure Nd2Fe14B compound (⁓585 K). The magnetic properties initially increased as a result of Alnico element substitution, and then slightly decreased. Maximum energy density of 100 kJ/m3 and Curie temperature of 582 K is obtained by substituting 15% Alnico. These properties are comparable to Ce-free Nd-Fe-B melt spun alloys. The working temperature range increased by the increase of Curie temperature and the decrease of spin reorientation temperature. Due to the accumulation of ferromagnetic element, Ni, at the grain boundary and triple junction phases and the refined grains, the short-range exchange interactions among the nanograins increased which helped to obtain high energy density in the alloys.

The (Nd1−xCex)31.5Fe67.5B1 (x = 0, 0.15, 0.2, 0.25, 0.3, 0.5, 0.75 wt%) alloys were prepared by rapid solidification method. It is found that the coercivity, Hci, abnormally increased to 1427.33 kA/m at x = 0.2. With the change of Ce content, the valence state of Ce shifted between 4 f 1 (+3) state and 4 f 0 (+4) state. In the x = 0.2 ribbon, the Ce3+ has a high proportion, which is beneficial to the magnetic hardening of Ce2Fe14B type permanent magnetic materials. Meanwhile, the higher proportion of large radius Ce3+ and a lower proportion of small radius Ce4+ promoted the discrete change of the lattice parameters. The first principle calculations showed a large variation of lattice parameters with different Ce substitution occupying different positions. As a result, lattice distortions and scattered stress fields are formed inside the alloy. Such fields have high domain wall energy which hinder the movement of the domain walls during the process of reverse magnetization.

Post-sinter annealing is essential to improve the microstructures and magnetic properties in NdFeB-based sintered permanent magnetic materials. In this paper, investigated systemically are the effects of post-sinter annealing on the microstructures and magnetic performance of Ga and Cu co-doping Nd2Fe14B based sintered magnets. It is found out that the intrinsic coercive force of the magnets increased from 9.17 kOe to 18.67 kOe after two stage post-sinter annealing (PSA), which shows an extraordinary increment of 103.5%. The remanence, with a decreasing percentage of 1.95%, slightly decreases from 13.87 kGs to 13.60 kGs. The substantial increase of intrinsic coercivity is mainly attributed to the improvement of clean and thin continuous grain boundary layers, the smoothness of hard magnetic matrix phase and the appearance of the RE6(Fe, M)14 antiferromagnetic phase during annealing. The reduction of the remanence is caused by the deteriorated orientation degree and reduced volume fraction of hard magnetic main phases after post-sinter annealing.

Oxide coated nanocomposite NiO@FeNiMo with core–shell structure were fabricated by plasma arc-discharging and oxidative heat treatment method. By optimizing the impedance matching, the absorbing properties of the oxide coated core–shell NiO@FeNiMo were improved significantly. By varying the coating thickness from 1.0 ∼ 5.0 mm, the reflectivity of less than −10 dB, in the frequency range of 4–17 GHz, was obtained in NiO@FeNiMo nanocomposites oxidized at 473 and 498 K. The minimum reflectivity of −54.0 dB at 12.8 GHz (d = 1.47 mm) was achieved by oxidizing the sample at 473 K. The oxide coated core–shell NiO@FeNiMo absorber reported in this paper have the potential be a powerful candidate for microwave absorbing materials for its excellent absorption, simple preparation process, and high stability in complex environments.

In this article, heat transfer analysis is performed for Magnetohydrodynamic (MHD) water based Single Wall Carbon Nanotubes (SWCNTs) inside a C-shape cavity that is partially heated along the left vertical wall in the presence of magnetic field. The convection inside the cavity due to the temperature difference along the sides of the walls give rise in the temperature and the complete structure is based upon the system of nonlinear coupled partial differential equations. Governing equation are further modified in term of effective thermal conductivity expression that depends upon the radius of nanoparticle and fluid molecule. These equations are solved via Finite Element Method (FEM) utilizing Galerkin approach. The results are presented and analyzed in the form of streamlines, isotherms and Nusselt number for emerging physical parameter, that are, Rayleigh number ( 10 4 ⩽ Ra ⩽ 10 6 ) , Hartmann number ( 0 ⩽ Ha ⩽ 200 ) and nanoparticle volume fraction ( 0 ⩽ ϕ ⩽ 0.2 ) . The study reveals that increase in Rayleigh number enhances the heat transfer rate and increase in magnetic field strength decreases it. For the considered range of nanoparticle volume fraction ( 0 ⩽ ϕ ⩽ 0.2 ) have significant impact on the temperature distribution. It is finally concluded that increase in the Rayleigh number enhances the stream flow and isotherms behavior. However, increase in Hartman number decreases the heat transfer rate inside the cavity.

Theoretical investigations are carried out to study hybrid SPP wave propagation along the Chiral-Graphene-Metal (CGM) interface. The Kubo formulism is used for the physical modeling of single-layer graphene and the impedance boundary conditions approach is applied at the CGM interface to compute the dispersion relationship for hybrid SPP waves. It is demonstrated that the chirality (ξ) and chemical potential (μc) parameters can be used to modulate the resonance surface plasmon frequencies of the upper and lower propagating modes. Furthermore, the propagation bandgap between the upper and the lower modes can be tuned by changing the chirality parameter. The effect of the chemical potential (μc)and the relaxation time (τ) on the normalized propagation constant, propagation length, and the effective refractive index is studied. The present work may have potential applications in optical and chiral sensing in the terahertz frequency range.

Reducing the spatial dimension of ferromagnetic (α1) phase is the most promising route for coercivity enhancement of alnico alloys. It is an experimental fact that the spatial dimension of α1 phase cannot be reduced below a certain limit (∼25 nm) using conventional processing methods. To obtain finer α1 phase we have fabricated alnico ribbons with nominal composition of 32.2Fe-36Co-13.5Ni-7.6Al-6.2Ti-3.8Cu-0.5Zr-0.2B by melt spinning and subsequent heat treatments. Very fine Fe-Co rich (α1) rods of the order of 5 nm diameter and 100 nm length embedded in Al-Ni rich matrix are obtained. After simplified heat treatment the properties of the isotropic ribbons are Hcj = 770 Oe, Br = 6.5 kGs and (BH)max = 1.86 MGOe. It is shown that alnico ribbons have unprecedented thermal stability described in terms of temperature coefficient of remanence (α) and temperature coefficient of coercivity (β) by measuring magnetic properties at high temperatures (∼800 K). The microstructures of the alloys have been analyzed by Optical Microscope, Scanning Electron Microscope and Transmission Electron Microscope. The phase transition temperatures have been observed by DTA and magnetic properties are measured by PPMS.

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Alnico alloys are prepared with nominal composition of 31.4-xFe-7.0Al-36.0Co-4.0Cu-1.0Nb-14.0Ni-6.0Ti-0.6Zr-xB (x = 0.02, 0.04, 0.06, 0.08, in wt%) by arc melting and casting techniques and subsequent heat treatment. The alloys are characterized by X-ray diffraction method, optical microscope, scanning electron microscope and pulse field magnetometer by plotting magnetic hysteresis demagnetization curve. The results of HRSEM show at least two new phases at α-grain boundaries and triple junctions. These phases, when retained at low concentration, help in enhancing magnetic properties of alnico alloys by purifying spinodal phases and reducing the adverse effects of impurity elements. Two different heat treatment cycles are employed. In the first phase, the alloys are processed by using heat treatment cycles without magnetic field; and Hc of 1.35 kOe, Br of 4.87 kGs and (BH)max of 1.96 MGOe are obtained by furnace cooling below TC and subsequent tempering at 680 °C and 550 °C. In the second phase, the alloy with best magnetic properties is treated thermo-magnetically; and Hc of 1.68 kOe, Br of 7.1 kG and (BH)max of 4.45 MGOe are obtained.

Grain boundary diffusion of Tb and Al elements can improve the coercivity and optimize grain boundary of NdFeB magnets. In this paper, we investigated magnetic property and microstructure evolution of sintered NdFeB magnets by grain boundary diffusion Tb80Al20 alloys. The coercivity and thermal stability of the magnets were effectively improved. Microstructural analysis confirmed the formation of Tb-rich shells and continuous grain boundary, contributing to coercivity enhancement of magnet. The element distribution and diffusion mechanism of the magnets have been disused. This work may shed light on developing low heavy rare earth sintered NdFeB magnets.

By combining rare earth-based Ce-Fe-B and rare earth free Alnico powders, composite Ce-Fe-B/Alnico spark plasma sintered (SPS) magnets have been fabricated and reported for the first time. It is observed that the two phases exit in the alloys interacting magnetostatically. The Alnico phase constitutes α1 and α2 phases as a consequence of spinodal decomposition process, while the Ce-Fe-B phase contained Ce2Fe14B and CeFe2 phases. By increasing the content of Alnico phase, the remanence magnetization and the maximum energy density of the composite alloys increased owing to the higher saturation magnetization of Alnico phase. Magnetic properties, such as remanence magnetization Js = 0.93 T, intrinsic coercivity Hcj = 202 kA/m and maximum energy density (BH)max = 19.8 kJ/m3 were obtained in spark plasma sintered composite magnets containing 15 wt% Alnico. The recoil loops demonstrated the presence of anisotropy variations in the alloys specifically at high applied magnetic field. Analysis of the Curie temperature and elemental analysis validated that the constituent phases of SPS magnets exist in the alloys. This work may shed light on the development of composite magnets with distinct phases and enhanced magnetic properties.

We report anisotropic magnetocaloric effect and magnetoresistance in antiferromagnetic HoNiGe3 single crystal grown by Ge flux method. HoNiGe3 single crystal exhibits antiferromagnetic order and large magnetocrystalline anisotropy below the Neel temperature TN = 10.5 K. Meanwhile, with increasing the magnetic field, HoNiGe3 undergoes the spin-flip transition induced by the magnetic field along the a axis, while the spin-flop transition occurs for the field along the other orientations, which gives rise to anisotropic magnetoresistance behavior along three axes. With the magnetic field change of 0–50 kOe, the maximum magnetic entropy changes obtained along the a, b, and c axes are −13.9, 2.5 and −7.7 J kg−1K−1, respectively. The maximum rotating magnetic entropy change is −12.3 J kg−1K−1 under 50 kOe by rotating the magnetic field from the b axis to the a axis, and the corresponding refrigeration capacity is 193 J/kg, which demonstrates HoNiGe3 to be an attractive candidate for novel rotating magnetic refrigeration at low temperature region.

In this paper, the effects of Hf addition on phase composition, Curie temperature, exchange coupling effect, coercivity mechanism, room temperature magnetic properties, high temperature magnetic properties and thermal stability of NdFeB alloys with different Nd content (27–31 wt%) are systematically studied. Hf addition showed different effects on the magnetic properties of NdFeB alloys at different Nd contents and different test temperatures. At 300 K, the intrinsic coercivity is increased with low Nd content (27 wt%), while the remanence and the maximum magnetic energy product are significantly improved with higher Nd content (29 wt%, 31 wt%). At 398 K, the intrinsic coercivity, the remanence, the maximum magnetic energy product and the temperature stability improved in NdFeB alloys with high Nd content (29 wt%, 31 wt%).

Strain engineering of graphene is a widely researched topic of the decade, one can realize the unique applications of graphene due to the strain affect. Doping in graphene is one of the methods to introduce strain and rare earths (RE) doping in graphene is a challenging task as the size of RE-atoms is much bigger compared to carbon. Herein, neodymium (Nd) is doped in graphene foam (GF) successfully, with the help of double-zone chemical vapor deposition (CVD) at hollow sites (interstitial doping). The doping is confirmed from several characterization tools and magnetotransport properties are detected afterword's. An extremely large positive magnetoresistance (PMR ∼ 1410% at 5 K under 8 T applied magnetic field) is observed in Nd-doped GF compared to as-grown GF (PMR ∼ 250% at 5 K under 8 T applied magnetic field). The PMR afterward starts decreasing upon the fabrication of Nd-composite at high temperature ∼1400 °C. Technologically, topological band structure of graphene upon doping influences the path of charge carriers as a result, a change in fermi-surface occurs, due to which unique applications can be realized.

Alnico-8 permanent magnets were produced through casting and subsequent thermal treatment process. Magnetic alloy of nominal composition 32.5 Fe-7.5 Al-1.0 Nb-35.0 Co-4.0 Cu-14.0 Ni-6.0 Ti were prepared by arc melting and casting technique. The Zr was added to 32.5 Fe-7.5 Al-1.0 Nb-35.0 Co-4.0 Cu-14.0 Ni-6.0 Ti alloy ranging from 0.3 to 0.9 wt%. The magnets were developed by employing two different heat treatment cycles known as conventional treatment and thermo-magnetic annealing treatment. The samples were characterized by X-ray diffraction method, Scanning electron microscope and magnetometer by plotting magnetic hysteresis demagnetization curves. The results indicate that magnetic properties are strongly depended upon alloy chemistry and process. The 0.6 wt% Zr added alloys yielded the best magnetic properties among the studied alloys. The magnetic properties obtained through conventional heat treatment are Hc = 1.35 kOe, Br = 5.2 kG and (BH)max = 2 MGOe. These magnetic properties were enhanced to Hc = 1.64 kOe, Br = 6.3 kG and (BH)max = 3.7 MGOe by thermo-magnetic annealing treatment.

In this paper, Cu element was added to the grain boundary of sintered Nd-Fe-B magnet to form a low melting point alloy phase in the grain boundary to promote the diffusion depth of Tb element. The intrinsic coercivity of the magnet with 0.2 % Cu addition increased significantly from 16.07 kOe for standard alloy without Cu to 24.38 kOe after the diffusion of TbF3 . The squareness of the demagnetization curves is maintained at 94 %, ensuring a good diffusion efficiency and uniformity. EPMA analysis showed that the distribution depth of (Nd, Tb) 2 Fe 14 B core-shell layer of the magnet was increased from 50 μm to 145 μm after the diffusion. The addition of Cu increased the ratio and average area of the grain boundary phases effectively, and formed a good diffusion channel. A larger amount of (Nd, Tb) 2 Fe 14 B shell layers formed in the magnet as a result of TbF 3 diffusion in Cu added magnets and which increased the intrinsic coercivity due to enhanced magnetocryalline anisotropy and favorable microstructure.In this paper, Cu element was added to the grain boundary of sintered Nd-Fe-B magnet to form a low melting point alloy phase in the grain boundary to promote the diffusion depth of Tb element. The intrinsic coercivity of the magnet with 0.2 % Cu addition increased significantly from 16.07 kOe for standard alloy without Cu to 24.38 kOe after the diffusion of TbF3 . The squareness of the demagnetization curves is maintained at 94%, ensuring a good diffusion efficiency and uniformity. EPMA analysis showed that the distribution depth of (Nd, Tb) 2 Fe 14 B core-shell layer of the magnet was increased from 50 μm to 145 μm after the diffusion. The addition of Cu increased the ratio and average area of the grain boundary phases effectively, and formed a good diffusion channel. A larger amount of (Nd,Tb)2Fe14B shell layers formed in the magnet as a result of TbF3 diffusion in Cu added magnets which increased the intrinsic coercivity due to enhanced magnetocryalline anisotropy and favorable microstructure.

The grain boundary diffusion process (GBDP) has become an important technique in improving the coercivity and thermal stability of Dy-free sintered Nd-Fe-B magnets. The influence of Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys by the GBDP on sintered Nd-Fe-B magnets are investigated in this paper. After diffusing Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys, the coercivity (Hcj) of the magnets increased from 13.58 kOe to 20.10 kOe and 18.11 kOe, respectively. Meanwhile, the remanence of the magnets decreased slightly. The thermal stability of the diffused magnets was improved by the GBDP. The microstructure shows continuous Rare-earth-rich (RE-rich) grain boundary phases and (Dy, Pr/Nd)2Fe14B core-shell structures which contribute to improving the coercivity. Moreover, the Dy concentration on the surface of the (Pr75Dy25)70Al10Ga20 diffused magnets decreased with the Pr substitution for the Dy element. The openness of the recoil loops for the (Pr75Dy25)70Al10Ga20 diffused magnets is smaller than that of the original magnets and Dy70Al10Ga20 diffused magnets. The results show that the (Pr75Dy25)70Al10Ga20 alloys can effectively optimize the microstructure and improve the magnetic properties and thermal stability of the sintered Nd-Fe-B magnets.

Nd-Fe-B alloys have high intrinsic coercivity, high magnetic energy density, but low Curie temperature and poor temperature stability. While Alnico alloys have high Curie temperature and high temperature stability, but low intrinsic coercivity and low magnetic energy density. It would be of great scientific, technological and economical interest if these two alloys could be combined together in some proportion to make composite magnets with good comprehensive properties. Here we report nanocrystalline composite magnets containing Nd-Fe-B hard phase and alnico semi-hard phase fabricated by melt-spinning technique. A novel core-shell like structure constituting Nd-Fe-B (2:14:1) phase as core and Alnico rich phase as shell was obtained by optimizing the composition and processing conditions. The maximum energy density was enhanced upto 150 kJ/m3 in nanocomposite magnets. The Curie temperature of the main phase increased to 654 K for Nd-Fe-B/Alnico from 581 K for pure Nd-Fe-B alloy, which is attributed to the molecular field penetration of Alnico phase into the hard 2:14:1 phase, in addition to the substitution of Fe by Co and Ni. No kink or dip was observed in the demagnetization curves, which suggested the presence of strong exchange interactions among the phases of the nanocomposite alloys.

Reducing the spatial dimensions of spinodally decomposed phases and enhancing their magnetization difference is a promising route for enhancing the magnetic properties of Alnico alloys. In this paper we report the effects of various heat treatments on the formation of spinodal phases and magnetic properties of Alnico cast alloys. After optimizing the heat treatment conditions, small amount of refractory element Ta is introduced into the alloys and the effect of Ta on the formation and purity of spinodal phases, magnetic properties and phase transition temperatures are investigated. The addition of Ta element improved the intrinsic coercivity (Hcj) of the alloys from 1.52 kOe for standard alloy to 1.83 kOe for 0.6% Ta, while the remanence (Jr) remained nearly unchanged. Scanning electron microscopy analysis confirmed the rod-like Fe–Co rich (α1) phase embedded in Al–Ni–Cu–Ti rich matrix phase. A volume fraction of higher than 67% is obtained for α1 phase, while an ameliorating effect of γ-phase suppression at grain boundaries and triple junctions was noted. The alloy with optimized composition possessed extraordinary thermal stability in the temperature range 300–800 K, which is attributed to the shape anisotropy and uniformly distributed nano mosaic structure. Finally, the interaction mechanisms in Alnico alloys were investigated by means of Henkel plot and the motor applicability was analyzed by recoil loops.

In this work, Sm24.6Co50Fe17·4Cu5·7Zr2.3-xHfx (x = 0–2.0) ribbons and magnets were prepared by melt-spinning method and spark plasma sintering (SPS) technique. The magnetic properties of the melt-spun ribbons with Hf addition are much higher than those of the Hf-free ribbons in the temperature range of 300–400 K. The optimal comprehensive magnetic properties of ribbons and isotropic magnets were obtained with 1.0 wt% Hf substitution. Microstructural results showed that Hf elements do not enter into the hard magnetic 1:7H and 2:17R phase in SPSed magnets and Zr–Hf rich phases are formed around grain boundaries as particulates. The enhancement of magnetic properties of the ribbons and SPSed magnets can be attributed to grain refinement and more uniform microstructure as a result of Hf addition. The micro-twin structure of 2:17R phase also have been discovered in the spark plasma sintered magnets. This work may provide a rapid preparation of Sm2Co17 magnets.

The high magnetocrystalline anisotropy of the Dy or Tb core shell structure formation can greatly improve the coercivity of sintered NdFeB magnets. In this work, we fabricated the base NdFeB magnet with Dy core-shell structure by double alloy method, and then diffusion TbH2 on the base NdFeB magnet. The result showed that compared with the base magnets, the coercivity of diffusion magnet increased by 7.6 kOe with a slight reduction in remanence. The thermal stability and the microstructure of the diffused magnet improved significantly. Microstructure analysis found that a Tb - Dy double-layer core-shell structure formed around Nd2Fe14B grains after diffusion. The double-layer core-shell structure can effectively prevent the reversed magnetic domain nucleation, and improve the utilization of heavy rare earths. This work may shed light on developing low heavy rare earth NdFeB magnets with high coercivity through controlling core-shell structure.

A hexagonal Ni2In-type single phase is obtained in the (Mn0.7Cu0.3)66Ga34 sample. The superspin glass (SSG) behavior and exchange bias effect are investigated in depth. The DC thermomagnetic M(T) measurements show a remarkable bifurcation between the zero-field cooling and field-cooling patterns below 100 K, suggesting a SSG behavior, which is verified by the simulation of de Almeida–Thouless relation from M(T) curves under different fields. Furthermore, the SSG behavior is justified by the AC susceptibility, temporal magnetic relaxation, and memory effect measurements. The asymmetric response of memory effect clearly indicates that it supports the hierarchical model. More importantly, the fitted parameters including Mydosh parameter Φ = 0.0255, dynamical critical exponent zv = 10.02, and τ0 ~ 5.5 × 10−9 s give the convincing evidences for the SSG behavior at low temperatures for (Mn0.7Cu0.3)66Ga34. Above all, a giant exchange bias field of μ0HEB = 308.4 mT is obtained at T = 2 K under the cooling field μ0HCF = 0.5 T and maximum applied magnetic field |μ0Hmax| = | +μ0H | = | −μ0H | = 8 T. The origin for giant exchange bias effect is discussed.

We report the observation of the giant topological Hall effect near room temperature in a complex noncollinear ferromagnet NdMn2Ge2 single crystal. Three successive magnetic transitions are observed below 400 K, including a spin reorientation transition at TSR = 215 K. The complex noncollinear magnetic structures give rise to anomalous transport behaviors. When the current flows along the a axis and the magnetic field is applied along the c axis, the anomalous Hall effect is observed, which is found to be dominated by the skew scattering mechanism. Strikingly, a giant topological Hall effect appears in a wide temperature range, which stems from the noncollinear spin configuration with finite scalar spin chirality. The topological Hall resistivity reaches the maximum of −1.35 μΩ cm at 300 K and drops slightly with temperature until below TSR. These results suggest that the NdMn2Ge2 single crystal would be a promising topological material for spintronic applications at room temperature.

In this work, we have investigated the structural and magnetic properties of hexagonal Lu0.5(Sc1-xInx)0.5FeO3 ceramics synthesized by solid state reaction. All samples were identified to crystalize in the hexagonal structure with polar space group (P63cm). The lattice parameters, both a and c, increase with In-substitution, owing to larger ionic radius of In3+ in comparison with that of Sc. Meanwhile, the c/a ratio increases from 1.9952 for x = 0 to 2.0308 for x = 1.0. All samples undergo an antiferromagnetic transition, accompanied by a dielectric anomaly, which is the fingerprint of magnetoelectric coupling in hexagonal LuFeO3 systems. The Neel temperature (TN) shifts towards lower temperature with the increase of In-substitution, demonstrating the weakening magnetic interaction stemming from smaller structural distortion due to smaller tilting angle of FeO5 bipyramids. It is fascinating that the increase of c/a ratio brings about a decrease of TN after the In-substitution for Sc. Another magnetic anomaly was observed above the TN (around 265 K) in Lu0.5Sc0.5FeO3. The temperature of magnetic anomaly increases towards higher temperature with the increase of In-substitution and rises above room temperature in Lu0.5In0.5FeO3. It can be suggested that the magnetic order is more complex than that obtained in previous works, and the room-temperature multiferroics is attainable for application in hexagonal RFeO3 systems.