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Rare-earth iron-boron (RE-Fe–B) thin films with a c-axis texture were prepared on a Ta (110) buffer layer on thermally oxidized Si substrates by dc magnetron sputtering. The microstructure, magnetic structure, and magnetic properties of these films were studied as a function of the deposition temperature. The results show that c-axis texture can be obtained over a wide range of deposition temperatures and that the degree of c-axis orientation improves with deposition temperature. It was established that deposition of a RE-Fe–B thin film to obtain grains with a strong c-axis RE2Fe14B texture, coexisting with an amorphous phase, followed by annealing at higher temperature, is an effective route for obtaining excellent hard magnetic properties. Initial results show that a film, which was deposited at 470 °C and annealed at 590 °C, had a high perpendicular coercivity of 1.8 T, in combination with a large maximum energy product of 238 kJ/m3. [ABSTRACT FROM AUTHOR]

To balance the utilization of rare earth (RE) resource and develop Ce-based permanent magnets with high performance/cost ratio, the role of La substitution in the melt-spun (Ce1−xLax)yFe14B (x = 0-0.4, and 0.5; y = 2-4) alloys has been investigated. It has been confirmed that the hard magnetic properties of Ce-based magnets can be effectively enhanced by partial substitution of La. The maximum (BH)max of (Ce,La)-Fe-B alloys can be obtained at a Ce:La atomic ratio of 7:3. The lattice parameters and Curie temperature of the hard magnetic (Ce/La)2Fe14B phase increase linearly with increasing La content. Three different alloy systems with y = 2, 2.5 and 3 show similar behavior of magnetic properties dependences on La. In the RE-rich compositions, La substitution for Ce can effectively inhibit the precipitation of the CeFe2 phase. A solid solution, Ce(La) phase with a space group of Fm-3m, appears in the (Ce0.7La0.3)yFe14B alloys with y ≥ 3.5. A good combination of magnetic properties with Hcj = 345 kA/m, J5T = 1.03 T, Jr = 0.60 T, and (BH)max= 6.3 MGOe is obtained in (Ce0.7La0.3)2.5Fe14B alloy. In addition, 30 at.% La substitution for Ce can significantly refine the grains, resulting in the enhancement of exchange coupling interaction. The present finding is beneficial for designing new and low-cost magnetic materials. [ABSTRACT FROM AUTHOR]

To reduce the cost of the Nd–Fe–B magnets, the Ce element was suggested to be used as a replacement of Nd element. In this paper, nanocrystalline (Ce1–xNdx)16Fe78B6 ( x = 0 –0.7) alloys were prepared by melt spinning. The X-ray diffraction (XRD) results indicate that the alloys are composed of (NdCe)2Fe14B (2:14:1) phase and (CeNd)Fe2 (1:2) phase for 0 < 0.6, and the 1:2 phase was replaced by (NdCe) _{1+\varepsilon } Fe4B4 (1:4:4) phase when x = 0.6 and 0.7. The hyperfine parameters characteristics of the 2:14:1 phases were estimated from 300 K 57Fe Mössbauer spectra, as well as their contents and those of other intergranular phases. In addition to the 2:14:1, 1:2, and 1:4:4 phases, a small content of the rare earth-rich phase was also detected in all the alloys, which was not able to be observed by the XRD characterization. Based upon the hyperfine field, the average magnetic moment of Fe in 2:14:1 phase could be determined as 1.56, 1.62, 1.67, 1.73, 1.78, 1.83, 1.85, and 1.91~\mu \text {B} for x = 0 , 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7, respectively. The minor change between the x = 0.5 ( 1.83~\mu _{\text {B}}) and x = 0.6$ ( 1.85~\mu _{\text {B}}) is discussed. Both the present local and macroscopic magnetic parameters significantly contribute to understand the fundamental role of Ce in those nanocrystalline Nd–Ce–Fe–B permanent magnets. [ABSTRACT FROM AUTHOR]

Conventional Sm–Co-based alloys have low glass forming ability, and thus are difficult to quench to nanocrystalline structure by rapid solidification. In this paper, nanocrystalline [Sm, rare earth (RE)] Co6.4Si0.3Zr0.3C0.2 (RE = Ce, Sm, Gd, Ho, and Er) alloys have been obtained by melt spinning after compositional modification, as prepared alloys have a microstructure consisting of TbCu7-type SmCo7-based nanocrystals with the mean size of approximately 20 nm surrounded by a soft amorphous phase and a cobalt phase. After annealing at 600 °C for 1 h, the alloys were well crystallized and the grains grew up to ~100 nm. Both the coercivity and the remanence have been enhanced significantly by annealing. The effects of the substituted RE elements on the magnetic properties and thermal stability were investigated. An annealed Sm0.8Er0.2Co6.4Si0.3Zr0.3C0.2 alloy showed the highest remanence of 0.59 T and (BH)max of 58.8 kJ/ \textm^3 . Excellent thermal stability with the remanence temperature coefficient $\alpha $ of −0.0178%/°C and −0.0778%/°C at temperature range of 27 °C~200 °C and 27 °C~400 °C, respectively, was also obtained. [ABSTRACT FROM PUBLISHER]

NdFeB bulk magnets were synthesized by spark plasma sintering (SPS) using the precursors of melt spun nanocrystalline Nd10.15Pr1.86Fe80.41Al1.67B5.91 ribbons mixed with Zn and/or Dy2O3 powders. The addition of 0.6 wt.% Zn or 2 wt.% Dy2O3 is effective in improving the magnetic properties of the magnets, and their coercivities are about 11% or 15%, respectively, higher than that of the additive free magnet. Both additives can suppress the grain growth of Nd2Fe14B phase. Dy2O3 is not beneficial to the densification during SPS, but Dy is considered to partly diffuse into the grains near particle boundaries and to form (Nd, Dy)2Fe14B phase. NdZn and NdZn5 phases were observed in the SPSed magnets with Zn additions more than 1 wt.%, which leads to coarse grains and porosities between the particles. The magnet with combined additions of 2 wt.% Dy2O3 and 0.6 wt.% Zn showed good thermal stability with small temperature coefficients and optimal magnetic properties with high coercivity and maximum energy product. [ABSTRACT FROM AUTHOR]

The magnetic properties and thermal stability of melt spun SmCo6.4Si0.3Zr0.3 ribbons with various rare-earth (RE) elements substituted for Sm have been investigated. It is verified that the properties’ combination of SmCo7-based ribbons can be modified by selected RE substitution. The light RE Ce is beneficial for enhancing the saturation magnetization and the remanence, while the coercivity and thermal stability can be significantly improved by heavy REs Gd, Ho, and Er substitutions. The highest room-temperature coercivity of 1467 kA/m was achieved in the Sm0.7Gd0.3Co6.4Si0.3Zr0.3 ribbon. For the temperature range of 27 °C–200 °C, Gd is the best element for enhancing the thermal stability, and the optimal temperature coefficients $\alpha $ and $\beta $ are −0.032%/°C and −0.269%/°C, respectively. For the range of 27 °C–400 °C, Ho is the best element to improve the thermal stability, and the values of $\alpha $ and $\beta $ are −0.064%/°C and −0.19%/°C, respectively. [ABSTRACT FROM AUTHOR]

Isotropic NdFeB permanent magnets were prepared by spark plasma sintering. Melt spun NdFeB ribbons with two compositions and four particle size ranges, i.e. 200-400, 100-200, 45-100 and <45 μm, were employed as the starting materials. For the magnets with Nd rich compositions, high density (7·5 g cm-3) and good magnetic properties with remanent magnetic polarisation Jr>0·8 T and maximum energy product (BH)max>100 kJ m-3 were obtained. The influence of particle size on the magnetic properties is not very significant. For single phase NdFeB alloys with stoichiometric 2:14:1 composition, because of the deficiency of Nd rich phases, it is relatively difficult to consolidate microsized powders into high density bulk magnet, but generally, a larger particle size is beneficial to achieve better magnetic properties, including higher Jr and (BH)max. [ABSTRACT FROM AUTHOR]

The effect of a variation in Si and N concentration on the microstructure, crystal structure and high-frequency magnetic properties of Fe–Co–Si–N nanogranular thin films was investigated. The films, prepared by rf magnetron sputtering, consisted of nanosized grains of FeCo as well as a Si and N rich intergranular amorphous phase. The Si concentration had a significant effect on the crystal structure of the FeCo phase. The resistivities of the Fe–Co–Si–N films were significantly enhanced by an increase in Si concentration. The resonant frequency of the Fe–Co–Si–N films could be tuned from 0.45 GHz to 2.1 GHz by controlling Si concentration. The N concentration greatly influenced magnetic properties and the variation in resonant frequency is in agreement with Kittel’s equation. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of polycrystalline GdCo9Si2 compound have been investigated. It has a BaCd11 structure and undergoes two magnetic phase transitions: an antiferromagnetic to ferrimagnetic transition occurring at ∼93 K, and a ferrimagnetic to paramagnetic transition at 420 K, which results in a positive and a negative magnetic entropy change, respectively. The two peak values of magnetic entropy change are -0.6 and 1.1 J·kg-1·K-1 for ΔH = 5 T. Furthermore, there exists a metal-semiconductor transition temperature (TP), below which the resistance increases with increasing temperature, while the semiconductor characteristic is observed above TP. The magnetic domain structures are characterized by stripe and grid structures 1 μm wide. Although the MCE is small for applications, its study is useful to clearly understand the nature of multiple magnetic phase transitions in the GdCo9Si2 compound. [ABSTRACT FROM AUTHOR]

The electronic structures and magnetic properties of spinel Co1-x Zn (Cd)xFe2O4 (x = 0.0, 0.25, 0.5, 0.75, and 1.0) have been studied systematically by the first-principles calculation. The optimized structures show that with increasing Zn (Cd) content the crystal lattice parameter increases by 1.47% (5.13%) when the Co ions are completely replaced by Zn (Cd) ions. The results also indicate that the magnetic moment of Co/Fe ion increases and the total spin magnetic moment linearly increases with the Zn (Cd) doping from 3.00 μB for x = 0.0 up to 10.00 μB for x = 1.0 per formula unit. The electronic distribution in the Co spin-down subband is highly localized for the crystal field splitting between t2g and eg levels in the Zn (Cd) doped CoFe2O4 compounds and the energy band moves downwards while doped with Zn (Cd). Meanwhile, the bandgap decreases with the increase of Zn (Cd) except where x = 1 and the spinel structure is half-metal at some degree of doping. [ABSTRACT FROM AUTHOR]

Crystal structure and magnetic properties of R5Sn4 alloys with R = Tb, Dy, Ho, and Er have been studied. R5Sn4, R11Sn10, and R5Sn3 phases coexist in the annealed alloys and the content of 11:10 and 5:3 phases varies between 9 and 17 wt.%. The R5Sn4 major phase has Sm5Ge4-type orthorhombic structure with space group Pnma. Tb5Sn4 has a complex magnetic structure, spin re-orientation and ferrimagnetic-paramagnetic phase transitions occur at ∼54 and ∼84 K, respectively. For Dy5Sn4, Ho5Sn4, and Er5Sn4, the antiferromagnetic-paramagnetic phase transitions occur at about 22, 15, and 8 K, respectively. The magnetic entropy changes (-ΔSM) of all alloys are negative at low temperature and changes to positive at higher temperatures, which could be attributed to the change of magnetic states. [ABSTRACT FROM AUTHOR]

Rapidly solidified nanocrystalline RE-TM-B (RE = Nd, Pr, Dy, TM = Fe, Co) alloys with enhanced hard magnetic properties were synthesized by melt spinning. The composition- and microstructure-dependent elevated temperature magnetic properties were investigated. The temperature coefficients of remanence (a) and coercivity (ß) were determined. The effects of Pr substituting Nd, Co substituting Fe, Dy substituting RE, and grain size on the Curie temperature and thermal stability were studied. Co or Dy substitutions were found to have a significant beneficial effect on the thermal stability. Reducing grain size could also improve elevated temperature behavior. Maximum energy product (BH)max > 100 kJ/m3 could be obtained in compositionally optimized nanophase alloys at temperature of 473 K. Extremely low coefficients of a and ß were realized in exchange coupled nanocomposite alloys. Bonded nanocomposite magnets with a = -0.052%/K and ß = -0.0365%/K for 300-400 K were also successfully fabricated. [ABSTRACT FROM AUTHOR]

The title alloys are prepared by arc melting the elements in Ar atmosphere and characterized by XRD, magnetic, and magnetocaloric measurements. [ABSTRACT FROM AUTHOR]

Ultrafine BaFe12O19 powders are prepared by sol-gel combustion using glycine gels prepared from metal nitrates and glycine solutions which are ignited in a furnace after drying (220 °C, 1 min) prior to calcination in air at 700-1000 °C. [ABSTRACT FROM AUTHOR]