Nanostructure, Composition, and Magnetic Behavior of Mechanically Alloyed Fe–Mo

Iron and molybdenum powder mixture exposed to stepwise mechanical alloying in air and in nitrogen is studied by X-ray diffraction, Mössbauer spectrometry, electron microscopy, magnetic measurements, and differential thermal analysis. The Mössbauer spectra are interpreted in terms of various contributions. The main contribution is associated with the FeMo nanograin core, which is similar to the bcc-FeMo bulk alloy of the same composition, i.e., a ferromagnetic solid solution of Mo in Fe. The increasing milling time contributes to a decrease in grain size. It results in a decrease of the volume fraction of the grain cores and simultaneously to an increase in a volume fraction of other contributions of highly defected surface zones and very close surface layers influenced by the milling atmosphere. The Rietveld interpretation of diffraction patterns, the scanning, and transmission electron microscopy completed by the EDX analysis and magnetic measurements are in good agreement with the Mössbauer spectra interpretation.     

Quenchability and Magnetic Properties of Nd_4Fe_(82)B_(14)

The glass forming ability (GFA), crystallization behaviour and magnetic properties of Nd4Fe82B14 produced by melt spinning were investigated. The experimental results show that the GFA is rather Strong; the crystals precipitation sequence is as follows: Am(amorphous)→Am'+bcc-Fe →Nd2Fe23B3+Fe23B6+bcc-Fe→Fe23B6+Fe3B+Nd2Fe14B+bcc-Fe→Fe3B+Nd2Fe14B+bcc-Fe. The magnetic properties after crystallization are not affected by the cooling rate and the best magnetic properties are Br=0.8436 T, Hcj=266.4 kA/m, (BH)max=48.08 kJ/m3.     

Mechanically Driven Alloying and Structural Evolution of Nanocrystalline Fe_(60)Cu_(40) Powder

Highly supersaturated nanocrystalline fcc Fe60Cu40 alloy has been prepared by mechanical alloying of elemental powders. The phase transformation is monitored by X-ray diffraction (XRD),Mossbauer spectroscopy and extended X-ray absorption fine structure (EXAFS). The powder obtained after milling is of single fcc structure with grain size of nanometer order. The Mossbauer spectra of the milled powder can be fitted by two subspectra whose hyperfine magnetic fields are 16 MA/m and 20 MA/m while that of pure Fe disappeared. EXAFS results show that the radial structure function (RSF) of Fe K-edge changed drastically and finally became similar to that of reference Cu K-edge, while that of Cu K-edge nearly keeps unchanged in the process of milling. These imply that bcc Fe really transforms to fcc structure and alloying between Fe and Cu occurs truly on an atomic scale. EXAFS results indicate that iron atoms tend to segregate at the boundaries and Cu atoms are rich in the fcc lattice. Annealing experiments show that the Fe atoms at the interfaces are easy to cluster to α-Fe at a lower temperature, whereas the iron atoms in the lattice will form γ-Fe first at temperature above 350℃, and then transform to bcc Fe     

Structural, Electronic and Magnetic Properties of Zinc-Blende Ga1−x TM x N (TM = Cr, Mn, Fe, V)

In this paper, we present a theoretical study of structural, electronic and magnetic properties for zinc-blende Ga_1?x TM _x N(TM = Cr, Fe, Mn, V) using the full-potential augmented plane wave (FP-APW) method with local-spin density approximation (LSDA). We have analysed the dependence of structural parameters values on the composition x in the range of x=0.25, x=0.50. Also, the role of p–d hybridisation is analysed by partial (PDOS) and total density of states (TDOS). The magnetic moment of Ga_1?x TM _x N has been studied by increasing the concentration of TM atom. The TM atom is the most important source of the total magnetic moment in these alloys, while the contributions from Ga and N are minor. In addition our results verify the half-metallic ferromagnetic character of TM doped GaN.     

Structural, Optical and Magnetic Properties of Ce�CGaN Based Diluted Magnetic Semiconductor

First ever Ce based GaN diluted magnetic semiconductor is reported. MOCVD grown GaN thin films were implanted with 3×10¹⁴ cm^?2 dose of cerium ions. Photoluminescence (PL), optical transmission, Raman, high-resolution X-ray diffraction (HRXRD) measurements were performed on samples to study the optical and structural properties of the materials. Band gap narrowing is observed in optical transmission measurements, which points to incorporation of cerium ions into GaN host lattice. Superconducting Quantum Interference device (SQUID) was used in order to investigate the magnetic properties of implanted samples as a function of temperature and applied field. Hysteresis loops were recorded at 100 K and 300 K for implanted and as-grown samples. Hysteresis behavior and temperature-dependent magnetization measurements revealed the presence of ferromagnetic ordering in Ce implanted GaN samples, which points to the realization of Ce:GaN diluted magnetic semiconductor.     

Structural and Magnetic Properties of RMO3 (R = Pr,Nd and M = Fe,Co) Perovskites

Journal of Superconductivity and Novel Magnetism - In this work, the RMO3 (R?=?Pr, Nd and M?=?Fe, Co) perovskites had been synthesized by hydrothermal method. The structural...     

Influence of Substitution of Transition Elements for Fe on the Structure and Magnetic Properties of the Nd_(16)Fe_(75)AI_2B_7 AHoy

1.IntroductionThe influence of substitution of variouselements for Fe on the magnetic propertiesof the Nd_(15)Fe_(77)B_8 alloy has been investi-gated by several authors,among which theAl substitution can increase the coercivity[1]and the addition of both Co and Al has beenproved to have a positive effect on im-proving both the coercivity and other per-     

Structural and Magnetic Properties of Sm_3(Fe,Ti)_(29) and Sm_3(Fe,Ti)_(29)X_y (X=H, N) Compounds

1. IntroductionRecelltly new intermetallic compounds NdZ(Fe,Ti)lo and RZ(Feo.91Vo.og)19 (R=Y, Nd, Sin, Gd) werediscovered by Collocott et al.II] and Shcherbakovaat al.IZ], respectively. The crystal structure of thesenew phases has been identified to be Nd3(Fe, Ti)29type structure using X-ray diffraction by Li et al.I3].Among them, the Sin3(Fe,Ti)29N. compound exhibitsstrong uniaxial anisotropy' and its saturation magnetization is very close to that of S.,Fe,,N;'] compound.The hydr…     

Structural, Electronic and Magnetic Properties of Nanolayer and?Bulk of MnCo2Si and MnFeCoSi Compounds

In the present work we have investigated the structural, electronic and magnetic properties of MnCo₂Si and MnFeCoSi in bulk and nanolayer using density functional theory. The total energies as a function of volume are calculated and thereby the bulk modulus and their pressure derivatives are determined. The effect of atoms at the surface of these nanolayers has been analyzed using the calculated total and partial electron density of states in its ferromagnetic phase. The spin-polarized density of states show that both bulk MnCo₂Si and MnFeCoSi present a half-metallicity, which is lost at their nanolayer surfaces. Furthermore, the effects of pressure on the magnetic moment of these compounds in its bulk form are investigated.     

Structure and Magnetic Properties of Nd-Fe-B/α-Fe Nanocomposite Magnets by Co, Nb, Dy Substitutions

1.IntroductionAlthoughtheremanenceofnanocompositemag-netsissignificafltlyenhanced,thecoercivityisgreatlydecreasedduetothepresenceofaquitequantityofsoftmagneticphase.Theoretically,ithasbeenpre-dictedthatasufficientlysmallgrainsizeofsoftmag-neticphaseisnecessarytocouplethehardgrainsinthenanocomposite[1l2].Infact,mostexperimentalresultstendtosupportthetheoreticalpredictionofthecriticalgrainsiz.sf3~6].However,inpracticeitisnoteasytoappropriatelycontrolthegrainsizeofnanocompositemagnets.Itiswellkn…     

First Principles Study of Structural, Magnetic and Electronic Properties of PbX (X= S and Se) Doped with B, C and N

Six ternary compounds PbA _0.75 M _0.25 (A=S and Se; M=B, C and N) with a NaCl structure were calculated to study the structure, electronic, and magnetic properties of them. The calculations were performed using the first-principles plane wave pseudopotential method within the generalized gradient approximation. The calculations reveal that ferromagnetism can be realized for C- and N-doping while B substitution does not induce magnetism in PbS and PbSe systems. The total energy calculations show that the ferromagnetic state is more stable as compared to a nonmagnetic state at their equilibrium lattices. Spin-dependent electronic band structure, total, and partial densities of state calculations demonstrate that the 2p-states of C- and N-dopants around Fermi level are responsible for ferromagnetism. Furthermore, equilibrium lattice constant, bond length, local magnetic moments, total magnetic moments, and robustness of ferromagnetism have been calculated. Particularly, the negative pressure calculations indicate that C-doping lead chalcogenides can change to half-metallic ferromagnetism materials.     

Structural and Magnetic Properties of Co(Cr1−y Al y )2O4 (y=0.0–0.2) Compounds

We present the structural and magnetic properties of Co(Cr_1?y Al _y )₂O₄ compounds prepared by the sol-gel technique for y=0.00,0.025,0.05,0.075,0.10,0.15 and 0.20. It has been observed that non-magnetic Al⁺³ substitution for Cr⁺³ enhances the magnetization at low temperatures compared to that of the parent compound. With increase in Al concentration spiral magnetic transition observed at around 24 K becomes less prominent, without affecting the ferrimagnetic transition temperature at around 97 K. The saturation magnetization values after subtracting the paramagnetic contribution vary from 0.036 μ_B/f.u to 0.376 μ_B/f.u. The enhanced ferromagnetic interaction and resultant magnetization could be explained in terms of decrease in Cr⁺³–O–Cr⁺³ bond angle with increase in doping concentration.     

The Role of Rare Earth (Y) Ions on the Structural,Magnetic and Mechanical Properties of Co–Mg Nanoferrites

The current paper is an effort to investigate the impact of rare earth yttrium on magnetic and mechanical properties of novel Co–Mg–Y nanoparticles. A series of ferrite nanoparticles, with a constant amount of cobalt and magnesium, substituted with various amounts of Y³⁺ as Co_0.7Mg_0.3Y_xFe_2-xO₄ (labeled as CMYF nanoferrites) were prepared and studied. The prepared CMYF samples were well investigated for structure and morphology utilizing x-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), and Fourier-transform infrared (FTIR) analysis. The crystallite size of CMYF nanoferrites introduced an abnormal behavior with further Y³⁺ substitution, ranging from 33.33 to 66.89 nm. The nanoferrite Co_0.7Mg_0.3Y_0.08Fe_1.92O₄ (x?=?0.08) has the highest coercivity (1410 G) within all CMYF samples, with increasing ratio 36.10% than the pristine Co–Mg nanoferrite. Also, the nanoferrite Co_0.7Mg_0.3Y_0.1Fe_1.9O₄ (x?=?0.1) has the highest resistance to uniform compression with increasing ratio 8.21% than the pristine nanoferrite. Shear and Young moduli introduced a peculiar trend: decrease regularly for 0.0?≤?x?≤?0.08 and then increase for the nanoferrite with x?=?0.1. Poisson’s ratio values confirmed that all CMYF nanoferrites are stable, isotropic, and linear elastic materials. Hosselman and Fulrath’s model was utilized to correct elastic moduli to zero porosity, which confirmed that porosity is a significant parameter for CMYF nanoferrite elastic moduli determination. Therefore, we conclude that Co_0.7Mg_0.3Y_0.08Fe_1.92O₄ nanoferrite can be utilized in storage media applications and Co_0.7Mg_0.3Y_0.1Fe_1.9O₄ nanoferrite in diverse ferrite standard mechanical applications.

     

Glass-Forming Ability for Nd_(70-x)Fe_(20)Al_(10)Y_x and Nd_(60-x)Fe_(30)Al_(10)Y_x Alloys

The glass-forming ability (GFA) of Nd70-xFe2oAl10Yx and Nd60-xFe30Al10Yx (0< x <15) alloys produced by Cu mold casting was investigated. Except Y=5 at. pct, bulk amorphous Nd70-xFe20Al10Yx alloys up to 2 mm in diameter were obtained. The GFA for Nd60-xFe30Al10Yx alloys, however, was found to decrease with increase of Y due to the increasing compositional deviation from the original eutectic point of Nd60Fe30Al10 alloy. The Nd60Fe20Al10Y10 and Nd60Fe30Al10 alloy exhibit the largest GFA and can be cast into bulk amorphous cylindrical specimens of 3 mm in diameter. The melting temperature or/and the reduced crystallization temperature is closely related to the GFA of Y-containing alloys. The bulk amorphous cylinder for the Nd55Fe20Al10Y15 alloy shows a distinct glass transition temperature and a wide supercooled liquid region before crystallization. The crystallization temperature, Tg, and the supercooled liquid region, TX, are 776 K and 58 K, respectively. The GFA and thermal stability of the Nd-Fe-AI-Y a     

Magnetic, Electrical and Thermodynamic Properties of UCuT x Al11−x Alloys Where T = Mn, Fe and x=4 and 5

The structure, magnetic, electrical, and thermodynamic properties of UCuT _x Al_11?x alloys, where T = Mn or Fe and x=4 or 5 are presented. The behavior of the Fe alloys is ferromagnetic-like with the Curie points amounting to 180 and 230 K, and the saturation magnetic moments under magnetic field of 5 T equal to 4.75 and 6.02 μ_B/f.u., respectively, whereas under a magnetic field of about 34 T the magnetic moments amount to 6.9 and 9.0 μ_B/f.u. for the alloys with x=4 and 5, respectively. The Curie points are reflected in the temperature dependence of the specific heat in which the anomalies are found at 180–200 and 230 K for alloys with x=4 and 5, respectively, however, it shows no reflection in the temperature dependence of the electrical resistivity. The field dependence of the magnetization at T=1.9 K for both compounds exhibits considerable hysteresis. There is a pronounced difference between ZFC and FC magnetization in its temperature dependence below the Curie point for materials with x=4 and 5. The Mn alloys exhibit ferrimagnetic-like character for which, supposedly, the interplay of the uranium and manganize sublattices is responsible. Magnetic transitions are determined at T _N =300 (x=4) and 380 K (x=5). However, those anomalies do not find confirmation in the temperature dependence of the specific heat and the electrical resistivity. Magnetic moments determined at T=1.9 K and in a magnetic field of 5 T are very low and in both cases amount to about 0.35 μ_B/f.u. and these values are slightly higher in a magnetic field of 34 T reaching a value of about 1.5 μ_B/f.u. Also for the Mn alloys the clear difference between ZFC and FC magnetization in its temperature dependence below the Curie point is observed.     

Instability of Structural, Magnetic, and Magnetoresistive Properties in Ordered Double-perovskite Sr_2FeMoO_6 Polycrystals

The problem of instability in polycrystalline ordered double-perovskite Sr2FeMoO6, is presented in this paper. By the X-raydiffraction analysis and the measuring of electrical and magnetic transports, it is indicated that the perovskite structure of thecompound is destroyed, and the Sr2FeMoO6 phase is mainly transformed into SrMo04 phase when the samples are exposedin damp atmosphere for several weeks or immersed in water for several hours. Simultaneously, their electrical and magneticproperties obviously change, and the value of magnetoresistance remarkably reduces and even vanishes at room temperature.A possible micromechanism of the instability and an effective method to avoid the problem of instability are also discussed.     

Structural and Electrical Transport Properties of Al1−xM x B2 (M = Li, Vacancy)

AlB₂ and MgB₂ are neighboring compounds and have similar crystal structures. However, their superconducting properties are very different because the σ holes which play a key role in the superconductivity of MgB₂ do not exist in AlB₂. In this paper we reported our attempts to dope holes into AlB₂ by substituting Li and vacancy for Al, and these holes were expected to induce superconductivity in the system. However, experimental results showed that Li was hard to substitute Al in AlB₂. The variation of resistivity with temperature and x for samples with the nominal composition of Al_1?xLi _x B₂ was analyzed by considering the phase variation of the samples with x. The temperature dependence of resistivity for Al_1?xB₂ was also studied and orders of magnitude change in resistivity was observed when x was up to 0.4 and 0.5, similar to that observed in Mg_1?xB₂ system by Sharma et al. (A. Sharma, N. Hur, Y. Horibe, C. H. Chen, B. G. Kim, S. Guha, Marta Z. Cieplak, and S. W. Cheong, Phys. Rev. Lett. 89, 167003 (2002)). It is proposed that phase separation may exist in Al_1?xB₂, leading to the dramatic change of resistivity because of percolation.     

Effect of Ni Doping on Structural,Morphological, Optical and Magnetic Properties of Zn1−x Ni x O Dilute Magnetic Semiconductors

Ni²⁺-doped ZnO diluted magnetic semiconducting materials (Zn_1?x Ni _x O with x=0.01,0.02,0.03,0.04,0.05) were synthesised by the co-precipitation method. All synthesised samples were sintered at 600 °C for 6 hours. The effects of Ni²⁺ ion-doping on the structural, morphological, optical and magnetic properties of ZnO were investigated using powder X-ray diffraction, field emission SEM, UV–DRS spectroscopy, photoluminescence and vibrating sample magnetometry. The XRD patterns of pure and Ni-doped ZnO samples revealed single phase hexagonal wurtzite structure. The SEM analysis revealed the morphology of prepared samples, and the chemical compositions of all samples were analysed using exhibit energy density X-ray analysis (EDAX) characterisation. The absorption and emission properties revealed the effect of Ni²⁺ doping in ZnO samples. All Ni²⁺ ion-doped samples showed ferromagnetism at room temperature. The observed results are here analysed and reported.     

Structure and Magnetic Properties of Fe_(76.5)Si_(13.5)B_9Cu_1 Alloy with Nanoscale Grain Size

The structure and magnetic properties of Fe76.5Si13.5B9Cu1 alloys with a nanocrystalline (NC) bcc Fe(Si) phase trom about 23 to 46 nm in diameter, which were first formed into amorphous ribbons and then annealed at various temperatures between 703 and 773 K, have been investigated. At annealing temperatures from 703 to 748 K, the single NC bcc(Si) phase is obtained in the crystallized alloys. The grain size and the Si-content in the NC bcc Fe(Si) phase for the alloys annealed at different temperatures are presented. The soft magnetic properties and the saturation magnetostriction for the alloys with the NC bcc Fe(Si) phase are also measured. The results show that, the saturation magnetizotion and the permeability are improved for the alloys with only the NC bcc Fe(Si) phase and become better with decreasing of the NC bcc phase size, and the saturation magnetostriction declines for the alloys with increasing Si-content in the NC bcc Fe(Si) phase.     

Diamagnetic and Electrical Properties of Si x Mo2S3−x (x=0.1, 0.2, 0.33, 0.5) and A0.1Mo2S3−x (A=C, B, and Ru)

Mo₂S₃ doped with Si, C, B, and Ru, is identified to bear the same crystalline structure P2₁/m as that of Mo₂S₃ through XRD analysis. Diamagnetic transitions with χ _m ～10^?4 emu/g?Oe at temperature ranging from 2 K to 6 K were observed in the doped samples of Si _x Mo₂S_3?x (x=0.1, 0.2, 0.33, 0.5). And both of the x=0.2 and 0.5 samples were found to have double diamagnetic transitions with higher T _c at the same temperature of 6.01 K, while Si _x Mo₂S_3?x of x=0.33 displayed an extra ferromagnetic-like response at 63 K. The corresponding transition in resistivity of Si _x Mo₂S_3?x with x=0.1 was noticed to show a mild drop with less than 10 % of its original transition values as measured down to 2 K. But a superconducting-like magnetic field dependence on the phase transition of resistivity was also noted. Its diamagnetic signals were greatly reduced when the applied magnetic fields were raised to 10³ Oes. In the doped samples of A_0.1Mo₂S_2.9 (A=C, B, and Ru), the phase transition in resistivity at 4.08 K, 4.62 K, and 4.35 K, respectively, exhibited similar fashion as that in the case of Si_0.1Mo₂S_2.9.