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The effect of Zr content on exchange coupling and magnetization reversal of the Nd 12.3 Fe 81.7– x Zr x B 6 ( x =0–3.0) ribbons was systematically investigated. Interaction domains were imaged by magnetic force microscopy (MFM). The strength of interactions determined by Wohlfarth's analysis increased first with Zr content x increasing, reached the maximum value at x =1.5, and then decreased with x further increasing. Initial magnetization curves and dependence of coercivity and remanence on applied magnetic field showed that the mechanism of coercivity in all samples was mainly of exchange coupling pinning type, which was enhanced with x increasing. It was found by three-dimensional atom probe (3DAP) that Zr atoms did not partition into the Nd 2 Fe 14 B hard magnetic phase, but significantly enriched at the interfacial region.

Nd12.3Fe81.7−xZrxB6.0 (x=0, 1.5) and (NdDyTb)12.3(FeZrNbCu)81.7−yCoyB6.0 (y=0, 12) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing. The influences of Zr, Dy/Tb and Co substitutions on magnetic properties and spin reorientation transitions of nanophase Nd2Fe14B have been systematically investigated. Compared with Zr-free sample, the remanence, intrinsic coercivity and maximum energy product for Nd12.3Fe80.2Zr1.5B6.0 ribbon increase by 10.8 %, 17.8 % and 60.2 %, respectively. The significant improvement of magnetic properties originates from the finer grains of the sample by introducing Zr, which leads to the stronger exchange coupling between neighboring grains. The intrinsic coercivity for (DyTb)-substituted ribbon is significantly increased although the remanence is reduced, which could be compensated by the substitution of Co for Fe. The spin reorientation temperature Tsr of nanocrystalline Nd2Fe14B alloys was determined by measuring the ac magnetic susceptibility. It was found to be lower than that of bulk Nd2Fe14B. The substitutions of Zr, Dy/Tb and Co result in reduction of Tsr. The smaller the grain size, the lower the Tsr will be. Influence of spin reorientation on magnetization characteristics of nanophase Nd2Fe14B was discussed.

The crystallization of single-phase nanocrystalline Nd10.8Dy1.5Fe79.7(NbZrCu)2.0B6.0 ribbons has been investigated. The as-spun ribbons are mainly composed of an amorphous matrix with a small amount of α-Fe, Nd2Fe14B and/or other crystallization phases. Cu-enriched clusters with different sizes have been found in the as-spun ribbons. These clusters almost disappear after crystallization, which can possess effects on the refinement of grains.

Effect of Zr addition on microstructure, magnetic properties and thermal stability of Nd12.3Fe81.7–xZrxB6.0 (x=0–3.0) ribbons melt-spun and annealed was investigated. Magnetic measurement using vibrating sample magnetometer (VSM) revealed that Zr addition was significantly effective in improving the magnetic properties at room temperature. The intrinsic coercivity Hci of the optimally processed ribbons increased monotonically with increasing Zr content, from 751.7 kA/m for x=0 to 1005.3 kA/m for x=3.0. Unlike the coercivity, the remanence polarization Jr increased first with Zr addition, from 0.898 T up to 1.041 T at x=1.5, and then decreased with further Zr addition. The maximum energy product (BH)max behaved similarly, increasing from 103.1 kJ/m3 to a maximum of 175.2 kJ/m3 at x=1.5. Microstructure studies using atomic force microscopy (AFM) and transmission electron microscopy (TEM) had shown a significant microstructure refinement with Zr addition. The absolute values of temperature coefficients of induction and coercivity were significantly increased with increasing Zr content, indicating that Zr was detrimental to thermal stability of the melt-spun Nd2Fe14B-type material.

Effects of Zr addition and annealing treatment on the formation, microstructure and magnetic properties of Nd12.3Fe81.7−x Zr x B6.0 (x=0−3.0) ribbons melt-spun and annealed have been systematically investigated by means of vibrating sample magnetometer (VSM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), and high resolution scanning electron microscopy (HRSEM). Phase analysis reveals that Nd2Fe14B is single-phase material. It has been found that the intrinsic coercivity H ci of the optimally processed Nd12.3Fe81.7−x Zr x B6.0 ribbons increases monotonically from 751.7 kA/m for x=0 to 1005.3 kA/m for x=3.0. The remanence polarization J r and maximum energy product (BH)max increase first with Zr addition, then slightly decrease with further increasing Zr content. Optimum magnetic properties with J r=1.041 T, H ci=887.5 kA/m and (BH)max=175.2 kJ/m3 have been achieved for the ribbons with x=1.5. The significant improvement of magnetic properties originates from the finer grains of the ribbons by introducing Zr.

Alloys of composition Nd 10.8 Dy 0.75 Tb 0.75 Fe 79.7− x Co x Zr 0.8 Nb 0.8 Cu 0.4 B 6.0 ( x =0, 3, 6, 9, 12, 15) were prepared by melt spinning at 22 m/s and subsequent annealing. Phase analysis revealed single-phase materials. Magnetic structure and remanence analysis indicated strong exchange coupling between neighboring grains in all samples. The remanence polarization J r and maximum energy product ( BH ) max increased first and then decreased with further increasing Co content x although the intrinsic coercivity H ci decreased with increasing x . The increase in remanence polarization J r by the substitution of Co for Fe is mainly caused by the increase in the saturation polarization J s rather than by the improvement of exchange-coupling interactions. Optimum magnetic properties with J r =1.041 T, H ci =944.9 kA/m and ( BH ) max =155.1 kJ/m 3 were achieved for x =12 ribbons. The mechanism of magnetic hardening in all samples was of pinning type by analyzing initial magnetization and the dependence on applied magnetizing field of the coercivity and remanence.

Effect of Co substitution and annealing treatment on the formation, magnetic properties and microstructure of (NdDyTb) 12.3 (FeZrNbCu) 81.7- x Co x B 6 ( x =0–15) ribbons prepared by rapid quenching and subsequent annealing was systematically investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and vibrating sample magnetometer (VSM). Phase analysis revealed single-phase material. The remanence polarization J r and maximum energy product ( BH ) max increased with increasing x from 0 to 12 and then decreased for x =15. The intrinsic coercivity H ci of (NdDyTb) 12.3 (FeZrNbCu) 81.7– x Co x B 6 ribbons optimally processed decreased from 1308.7 kA/m for x =0 to 817.4 kA/m for x =15. Optimum magnetic properties with J r =1.041 T, H ci =944.9 kA/m and ( BH ) max =155.1 kJ/m 3 were achieved by annealing melt-spun ribbon ( x =12) at 675 °C for 10 min. There was no significant influence of Co substitution on microstructure.

Giant magnetostriction TbDyFe alloys, with 〈1 1 0〉 orientation and designated TDT-110, were prepared by a zone melting directional solidification technique with a high temperature gradient. Samples in the as-grown and heat-treated states, having various magnetostrictive properties, have been studied by transmission and scanning electron microscopy. The results of microscopy studies indicate that the density and distribution of microstructural defects substantially influence the magnetostrictive strains for these alloys.

＜110＞ oriented rods of TbDyFe giant magnetostrictive alloys have been prepared with the help of the zone melting directional solidification technique with a high temperature gradient. To acquire optimal magnetostrictive properties at low magnetic field, the TbDyFe alloys have been heat-treated at different temperatures and cooled at different rates. The relationships between the process of the heat treatment, microstructure, defects, and magnetostrictive properties of the TbDyFe materials have been studied.

The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Interaction domains derived from strong exchange coupling interactions between hard and soft magnetic grains were imaged using magnetic force microscopy (MFM). Maximum remanence, intrinsic coercivity, and maximum energy product values were obtained in the ribbons annealed at 700°C for 15 min, which were composed of Pr2(Fe, Co)14B, α-(Fe, Co), and slight Pr2(Fe, Co)17 phases. Although Jr Hd, and (BH)max decreased gradually with further increase of annealing time, it is emphasized that comparatively high Jr and Hci and (BH)max were obtained in a wide annealing time period of 15 to 360 min. The shape of initial magnetization curves and hysteresis loops change as a function of annealing time, indicating different magnetization reversal routes, which can be fully explained by the corresponding microstructure.

In this paper five J – H curves, the magnetic polarization curves, which are come from five M – H curves, have been given. From these curves, by using the approaching saturation law, the anisotropy constants of corresponding alloys have been given. And the curve K 1 – x has been got. The variation of the curve K 1 – x has been discussed.

〈1 1 0〉 oriented rods of TbDyFe giant magnetostrictive alloy have been prepared by zone melting directional solidification method. Two steps heat treatments were performed at 1353 K for 2 h, followed by heating at 673, 773, 873, 973 K for 4 h in argon atmosphere and air cooling. The effect of a two steps heat treatment on the mechanical properties, fractography and magnetostriction of TbDyFe has been studied. It was found that the largest values of impact toughness, compression strength and magnetostriction were achieved when the alloy was heat-treated at 873 K. Room temperature Vickers indentation was performed to access the fracture toughness, and with heating temperature increasing from 673 to 973 K, the fracture toughness was gradually improved. The change of mechanical properties and magnetostriction of TbDyFe was due to a change of the relative dimensions and distribution of the rare earth-rich phase caused by the two steps heat treatment.

The magnetic properties and the phase structure of Tb 1− x Pr x Fe 1.96 ( x = 0 – 0.7 ) were studied. It is found that the saturation magnetization on easy axis is decreased with increasing of Pr content, from 77.24 Am 2 kg −1 for x = 0 , reduces to minimum value of 11.84 Am 2 kg −1 for x = 0.5 , and returns to 37.14 Am 2 kg −1 for x = 0.7 . The non-cubic phases appear beyond x = 0.2 and the matrix changes from TbFe 2 phase for x = 0 to (Tb, Pr)Fe 3 phase for x = 0.4 , at last to (Tb, Pr) 2 Fe 17 phase for x = 0.7 . The compound structures turn more complex as the Pr content increased.

〈1 1 0〉 oriented rods of TbDyFe giant magnetostrictive alloy have been prepared by zone melting directional solidification method followed a heat treatment for 2 h at 1173–1353 K under argon atmosphere. Effect of heat treatment on the mechanical properties and fractography of TbDyFe has been studied. It was found that the largest values of impact toughness and compression strength were achieved when the alloy was heat-treated at 1353 K. When the heating temperature was higher than the eutectic temperature, the impact toughness and compression strength were improved with heating temperature increasing. The change of mechanical properties was due to the alternation of morphology, size, distribution of rare earth-rich phase caused by heat treatment. The fracture mechanism of TbDyFe is cleavage fracture.

The magnetic properties and the phase Transformation of Tb1-xPrxFe1.96(x = 0 to 0.7) compounds were studied by means of vibrating sample magnetometer(VSM), X-ray diffraction(XRD) and SEM back-scattered electron (BSE). The result indicates that the saturation magnetization σs of compounds along an easy axis decreases with the addition of Pr contents, which reduces from 77.24 Am2 · kg−1 (x = 0) to 11.84 Am2·kg−1(x = 0.5) and then returns to 37.14 Am2·kg−1 (x = 0.7). The non-cubic phases appear when x exceeds 0.2, and the matrix of Tb1-xPrxFe1.96 compounds changes from (Tb, Pr)Fe2 phase with x = 0 to (Tb, Pr)Fe3 phase with x = 0.4, and at last to (Tb, Pr)2Fe17 phase in Tb0.3Pr0.7Fe1.96. Moreover, the structure of the compounds may become more complex with the increase of Pr content.

Nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons were prepared by melt-spinning and subsequent annealing. Interaction domains were imaged using magnetic force microscopy (MFM) because of strong exchange coupling between hard and soft magnetic grains. Coercivity was determined by exchange coupling pinning field. But the magnetization reversal of nanocomposite magnets were different from that of traditional single phase permanent magnets.

Effect of heat treatment on magnetostrictive properties and order-disorder transition of -oriented polycrystal Fe83Ga17 alloys is investigated. It is found that magnetostriction and order degree of Fe83Ga17 alloys are very sensitive to cooling rate. Variation of magnetostriction is discussed in terms of order-disorder transition. Under compressive stress of 20 MPa, saturation strain λs of partially ordered Fe83Ga17 alloys quenched into water reaches 298 × 10−6.

Phase transformations and magnetic properties of overquenched Pr 8 Fe 86 B 6 ribbons during annealing treatment have been investigated. The as-quenched structure of the ribbons was varied by changing the quenching rate during the melt spinning process. It was found that, depending on their as-quenched structures, the phase transformations of the ribbons during annealing may take place in one of the following sequences: (1) Amorphous phase (Am)+Pr 2 Fe 14 B+α-Fe→Pr 2 Fe 14 B+α-Fe; (2) Am+α-Fe→ Am′+α-Fe→α-Fe+Pr 2 Fe 23 B 3+ Pr 2 Fe 14 B→Pr 2 Fe 14 B+α-Fe; and (3) Am→Am′+α-Fe→Pr 2 Fe 23 B 3 +α-Fe→ Pr 2 Fe 14 B+α-Fe. However, for all the ribbons, the microstructure after optimal annealing was found to consist only of two magnetic phases: Pr 2 Fe 14 B and α-Fe. The optimum magnetic properties (intrinsic coercivity H ci and remanent polarization J r ), and the squareness of the demagnetization curves of the annealed ribbons deteriorated drastically with increasing quenching rate of unannealed precursors. This deterioration can be attributed to the formation of a coarser and more irregular microstructure during annealing of the samples initially melt spun with higher wheel speeds, which was confirmed by our TEM observations, analysis of the temperature dependence of coercivity and measurement of irreversible susceptibility.

X-ray diffraction and Mossbauer measurements indicate that melt spinning at different wheel velocities causes as-quenched Pr7Fe88B5 ribbons to have distinctive structures. Depending on their as-quenched structures, the phase transformations of the ribbons during annealing may take place in one of the following sequences: (1) amorphous phase (Am)+Pr2Fe14B+α-Fe→Pr2Fe14B+α-Fe; (2) Am+α-Fe→Am′+α-Fe→α-Fe+1:7 phase+Pr2Fe14B→Pr2Fe14B+α-Fe; and (3) Am→Am′+α-Fe→1:7 phase+α-Fe→ Pr2Fe14B+α-Fe. However, for all the ribbon samples, the microstructures after optimal annealing with respect to magnetic properties were found to only consist of two magnetic phases: Pr2Fe14B and α-Fe. The optimum magnetic properties of H c j and Jr, and the squareness of the demagnetization curves of the annealed ribbons deteriorate drastically with increasing quenching rate of unannealed precursors. Taking into account TEM results, the values of αex and Neff derived from the temperature dependence of the coercivity, these deteriorated effects can be attributed to the formation of a coarser and more irregular microstructure during annealing in the samples initially melt spun with higher wheel speeds.

Phase transformations and magnetic properties of overquenched Pr7Fe88B5 ribbons during annealing have been investigated. X-ray diffraction and Mossbauer measurement indicate that melt spinning at different wheel velocities caused the as-quenched ribbons to have distinctive structures. Depending on their as-quenched structure, the phase transformation of the ribbons during annealing may take place in one of the following sequences: (1) amorphous phase (Am)+Pr2Fe14B+α-Fe→Pr2Fe14B+α-Fe; (2) Am+α-Fe→Am′+α-Fe→α-Fe+1:7 phase+Pr2Fe14B→Pr2Fe14B+α-Fe; and (3) Am→Am′+α-Fe→1:7 phase+α-Fe→Pr2Fe14B+α-Fe. In all cases, the microstructure of the ribbons after optimal annealing was found to only consist of two magnetic phases: Pr2Fe14B and α-Fe. However, with increasing initial quenching rate, the microstructure of optimally heat treated ribbons becomes coarser and more irregular, and the magnetic properties of them deteriorated drastically. The δM plots, irreversible susceptibility, and the temperature dependence of coe...

Powder metallurgy technique was applied to prepare TbDyFe sintered compacts. Various processing parameters were explored to obtain high-density compacts. High Tb/Dy ratio alloy powders were used to improve axial 〈1 1 1〉-oriented grain-alignment in the compacts. Significant magnetostrictive ‘stress effect’ was observed in the grain-aligned compacts. Under a compressive pre-stress of 24 MPa, 1400 ppm magnetostriction was obtained in Tb 0.32 Dy 0.68 Fe 1.80 sintered compacts at the magnetic field of 7 kOe. This shows that the TbDyFe sintered compacts can exhibit much higher magnetostriction than random-grain TbDyFe polycrystals. The incomplete grain alignment and undesirable fine microstructure in the compacts led to their low low-field magnetostriction, compared to the crystals prepared by using crystal growth method. Reduction of oxidation during processing is crucial to obtain coarse microstructure.

High magnetostrictive strain has been obtained in Tb 0.3 Dy 0.7 Fe 1.98 polycystalline samples with crystal orientation. The λ 40 and λ 80 values are 1250 and 1550 ppm, respectively under a pressure of 6 MPa, which is better than that of samples with crystal orientation. The observed morphologies indicate that the grains with axial orientation grow in the form of sheet-like cellular crystals. A rare-earth rich phase (R = Tb, Dy), is distributed along the boundaries of the cellular crystals. The excellent magnetostrictive properties are related to the microstructure of the material.

The coercivity mechanism of Nd‐Fe‐B sintered magnets is investigated using a continuously varying model for a single variable K. The results show that the starting field Hs (which includes the critical field H0 and the expanding field He) is greater than the nucleation field Hn and is the main element that controls the coercive force in Nd‐Fe‐B sintered magnets. The comparison between theory and experiment on the dependence of coercivity on the field strength aligning the grains Ha indicates that the starting field theory is in better agreement with the experimental result than other theories discussed.

The crystal structure and microstructure of Sm 2 (Fe 1 − x Ga x ) 17 ( x = 0−0.12) have been studied by X-ray diffraction and scanning electron microscopy analysis techniques. Results indicate that the alloys have a single phase with Th 2 Zn 17 -type structure for x ⩽ 0.02; when x = 0.05−0.12, two phases, namely Sm 2 (Fe, Ga) 17 and (Ga, Fe)Sm, exist and, the higher the gallium substitution the more (Ga, Fe)Sm phase occurs. The lattice parameters increase with Ga addition. The Curie temperature and saturation magnetization of the nitrides decrease with increasing gallium substitution; however, the anisotropy field reaches a maximum value of 18.4 T for x = 0.02 at room temperature. The hard magnetic properties of the nitrides decrease also except for x = 0.02. The optimum hard magnetic properties obtained are B r = 12.3 kG, i H c = 10.0 kOe and ( BH ) max = 26.2 MG Oe with x = 0.02. The thermomagnetic curves measured of all the nitrides have shown that the onset decomposition temperatures are 760–780 K, which are slightly affected by gallium substitution.

The field dependence of the coercive field for isotropic and aligned Sm2Fe17Nx epoxy resin bonded magnets are investigated. Results indicate that the coercive field of the isotropic magnet is larger than that of the aligned magnet. For small magnetizing fields, the coercive field of the sample magnetized antiparallel to the alignment direction is larger than that of the sample magnetized parallel to the alignment direction of the magnets. When the magnetizing field is large enough, the coercivities obtained after magnetizing the aligned sample in parallel and antiparallel directions are the same. The microstructural parameter derived from the temperature dependence of the coercive field implies that both nucleation and pinning mechanism could be responsible for the magnetic hardening of the Sm2Fe17Nx epoxy resin bonded magnets.

Positive and negative interaction have been found to co-exist in Sm2Fe17Nx and Nd2Fe14B isotropic magnets. The measured positive interaction may come from the interactions from those grains with small deviation angle between its easy axis and the direction of external field, whereas the negative interaction may come from those grains with large deviation angle. The numerical calculations of the magnetostatic fields around a particle indicate that the positive interaction results from the magnetostatic interaction among nearest-particles located in forefront and backfront along their common easy axis of magnetizations and the negative interaction results from the magnetostatic interaction among those particles located in same plane perpendicular to their easy axis of magnetizations. In soft-hard multiphase materials, larger the remanence enhancement is, stronger the negative interparticle interaction becomes. The remanence enhancement in SmFeN materials have also been investigated.

In the present paper the nucleation as well as the pinning fields in Sm2Fe17Nx Sn-bonded material are analysed based on the well established micromagnetic theory. The microstructural parameters derived from the measured temperature dependence of the coercive field indicate that the coercive field in Sm2Fe17Nx Sn-bonded material is dominated by the nucleation field occurring in the inhomogeneous area near the grain surface. The magnetic phase transition at the Curie temperature from the ferromagnetic to the paramagnetic state of the magnetically soft phase Sm2Fe17 existing in Sm2Fe17Nx magnets leads to a decrease of the effective demagnetization factor. Furthermore the temperature dependence of the domain wall energy γ, the average exchange constant A, the domain wall width δB, as well as the critical diameter of a single domain particle Dc.

The coercivity mechanism of Sm2Fe17Nx hydrogen decrepitated magnets is analysed on the basis of micromagnetism. The discrepancy between the experimentally realized coercivity and the ideal nucleation field as predicted by Brown is also found in Sm2Fe17Nx magnets. This discrepancy is due to the effect of the microstructure. Our analysis strongly indicates that the coercivity in Sm2Fe17Nx hydrogen decrepitated magnets is controlled by the nucleation mechanism. The anisotropy constants K1, K2, and the saturation polarization Js of Sm2Fe17Nx in the temperature range from 200 to 620 K are determined from the analysis of the approach to ferromagnetic saturation. Der Koerzitivfeldmechanismus von durch Wasserstoffversprodung hergestellten Sm2Fe17Nx-Magneten wird unter Zugrundelegung der Theorie des Mikromagnetismus analysiert. Der Unterschied zwischen den experimentell festgestellten Koerzitivfeldstarken und dem von Brown vorhergesagten idealen Keimbildungsfeld wird auch im Falle der Sm2Fe17Nx-Magnete beobachtet. Dieser Unterschied wird auf die Rolle der Mikrostruktur zuruckgefuhrt. Unsere Analyse gibt starke Hinweise darauf, das das Koerzitivfeld in durch Wasserstoffversprodung hergestellten Sm2Fe17Nx-Magneten durch einen Keimbildungsmechanismus bestimmt ist. Im Temperaturbereich von 200 bis 620 K werden die Anisotropiekonstanten K1, K2 und die Sattigungspolarisation von Sm2Fe17Nx mit Hilfe einer Analyse der Einmundung in die ferromagnetische Sattigung bestimmt.

In the present paper, the angular dependence of coercivity for the Sm 2 Fe 17 C x magnets has been investigated in detail. Our results indicate that the angular dependence of the coercivity depends strongly on the coercivity value of the sample. For the sample of low coercivity with short hall milling time, the coercivity increases at first, develops a peak and then decreases with increasing angle between the easy axis and the direction of the external field. In contrast, minimum coercivity behavior has been observed in the sample of larger coercivity with longer ball milling time.

Microstructure evolution and magnetic properties of overquenched Pr8Fe86B6 ribbons during annealing have been investigated. The results showed that, in as-quenched state, the microstructure of the ribbons consists of a mixture of amorphous phase (Am)+Pr2Fe14B+a-Fe, Am+a-Fe and only amorphous phase, respectively, for the wheel speed of 22, 26, and 30 m/s. Depending on the overquenched precursor, the microstructure evolution of the ribbons during annealing can be classified into: (1) Am+Pr2Fe14B+a-Fe→Pr2Fe14B+a-Fe; (2) Am+α-Fe→Am′+a-Fe→a-Fe+Pr2Fe23B3+Pr2Fe14B→Pr2Fe14B+a-Fe; and (3) Am→Am+a-Fe→Pr2Fe23B3+a-Fe→Pr2Fe14B+a-Fe. In all cases, the microstructure of optimally annealed ribbon samples consist of magnetically hard Pr2Fe14B and soft magnetic a-Fe phases. The magnetic properties achieved by optimal annealing were found to be strongly dependent upon the initial quenching rate of the unannealed precursor. A fairly significant drop in both Hci and Br was observed with the increase of quenching rate of the p...

High coercivity, high remanence, and high energy product (NdDy)2(FeNb)14B–α–Fe nanocrystalline alloys containing 0 to 30 wt % α–Fe have been prepared by melt spinning and subsequent annealing. The best magnetic properties of remanence (Br), coercivity (Hci), and maximum energy product [(BH)max] are 1.02 T, 702 kA/m, and 134 kJ/m3, respectively, for Nd8.16Dy1Fe85.26Nb1B4.58. The microstructure consists of a two phase nanocomposite of hard magnetic (NdDy)2(FeNb)14B and soft magnetic α–Fe with an average size of about 30 nm. These small dimensions allow effective exchange coupling between hard and soft magnetic grains and result in the simultaneous enhancement of Br, Hci, and (BH)max. A systematic study on the effect of annealing temperature and time on the microstructure and magnetic properties has been carried out.

The intrinsic and hard magnetic properties of Sm 2 (Fe 1 − x Al x ) 17 nitrides were investigated. The Curie temperature and saturation magnetization decrease linearly with increasing Al concentration, as also does the anisotropy field at room temperature. The X-ray diffraction patterns have shown that all the samples exist in a nearly single phase with Th 2 Zn 17 -type structure for x up to 0.12. The lattice parameters increase with the substitution of Al for Fe atoms. The hard magnetic properties of the nitrides obtained indicate that the addition of Al has an unfavorable effect. The onset decomposition temperature of all nitrides derived from the thermomagnetic curves is around 750 K, implying that Al substitution could not improve the thermal stability of 2:17 nitrides.

In the present work, hard magnetic behaviours of (Sm1-yPry)2Fe17Nx magnets are investigated. Remanence enhancement is observed when some of the Sm atoms are replaced by Pr atoms in the compounds, which is due to the larger saturation magnetization of (Sm1-yPry)2Fe17Nx than of pure Sm2Fe17Nx. Meanwhile the coercivity of (Sm1-yPry)2Fe17Nx decreases with increasing Pr content in the compounds, which corresponds to the decrease of the anisotropy field in the compounds. In order to obtain a combined good effect on the remanence and the coercivity, the Pr content y should be no more than 0.4 in (Sm1-yPry)2Fe17Nx nitrides.

The ribbons with different thicknesses of Fe83Ga17 alloy were prepared by melt spun. The maximum magnetostriction of −2100ppm has been obtained in the ribbon with the thickness of 75μm. The microstructures of the ribbons were determined by x-ray diffraction. It was found that DO3 structure emerges in those ribbons melt spun at a higher cooling rate. This special DO3 structure is favorable to the enhancement of magnetostriction. It is considered that more short-range ordering of Ga atoms appeared when liquid alloy was solidified with a certain extreme cooling rate. Such short-range ordering of Ga atoms brings a local stress and results in the giant magnetostriction. The large demagnetizing magnetic energy in the normal direction of the ribbons causes the magnetic moments parallel to the ribbon plane. When an applied magnetic field is perpendicular to the ribbon plane, the magnetic moments turn 90° and generate giant magnetostriction.

The single phase of the high-Tc phase (107 K) in Bi-based system has been synthesized successfully for the first time by partial substituting of Pb for Bi and combined with adding more Ca, Cu based on Bi 2 Sr 2 Ca 2 Cu 3 O y formula. A long period of sintering at 880°C is necessary to get the sample and its good phase purity are proved by a.c. susceptibility measurement and the X-ray powder diffraction (XRD) analysis. The XRD pattern can be well assigned to an orthorhombic cell with a=5.418 Å, b=5.346 Å and c=37.10 Å.

The unfavorable effect of La on the magnetic properties of R‐Fe‐B permanent magnets is shown to be related closely to remarkable changes in microstructure due to excessive oxidation of La‐containing R‐rich phases in the alloys. Ce and Al are found to be effective in promoting the sintering process of La‐containing alloys, resulting in improvements in both microstructure and magnetic properties. Al segregates into the fcc R‐rich phase and improves the wetting ability of its liquid at high temperatures. It is suggested that the influence of Al on coercivities of R‐Fe‐B magnets is connected with a depression of magnetic interactions between hard magnetic grains.

The neodymium-rich phases in the NdFeB system have two different crystal structures before and after the conventional sintering process and a transformation from the double h.c.p. structure in the ingot to the f.c.c. structure in the sintered magnets is observed. The introduction of oxygen into the system during the process changes the ternary system into a quaternary system and the f.c.c. phase is a stable phase in the latter system. This phase absorbs the oxygen which enters into the system during the sintering process and at the same time acts as a sintering-aiding phase at high temperatures.

High Tc superconducting single phase of PbBiSrCaCuO with zero resistance temperature 107K has been prepared. The magnetization and upper critical field have been measured in an applied magnetic field up to 7T. Results show that the lower and upper critical field are Hc1 (0) = 900G, Hc2 (0) = 184T. Superconducting parameters Jc, Hco, ξoλo,k are estimated from experimental results.