Fe 100-x Research Articles

Microstructure and Magnetic Property of M-Type SrRE<SUB><I>x</I></SUB>Fe<SUB>12−<I>x</I></SUB>O<SUB>19</SUB> by Sol–Gel Method

Magnetoplumbite-type (M-type) SrRE(x)Fe(12-x)O19 (RE = La and Ce, x = 0-1.0) powders were prepared by a citric acid sol-gel technique and subsequent heat treatment. The crystal structure, grain size and magnetic properties were investigated by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and vibrating sample magnetometer (VSM). The XRD patterns show that SrRE(x)Fe(12-x)O19 (RE = La and Ce) are mainly hexagonal magnetic plumbite structure, and the average grain size of 30-40 nm was calculated using the Scherer's equation based on the XRD spectrum. Substitution of Fe ion by the rare earth La ion causes a significant decrease in intrinsic coercivity (Hc) and a slight decrease in saturation magnetization (Ms) as shown in the magnetization hysteresis loops. However, the Hc rises gradually in a small wave pattern with the increase of doping content of the rare earth Ce. The relation between the crystal structure and magnetic properties was also studied in this work.

Sublattice magnetism inσ-phaseFe100−xVx(x=34.4, 39.9, and 47.9) studied via zero-fieldV51NMR

The first successful measurements of a sub-lattice magnetism with 51V NMR techniques in the sigma-phase Fe(100-x)Vx alloys with x = 34.4, 39.9 and 47.9 are reported. Vanadium atoms present on all five crystallographic sites are magnetic. Their magnetic properties are characteristic of a given site, which strongly depend on the composition. The strongest magnetism exhibit sites A and the weakest one sites D. The estimated average magnetic moment per V atom decreases from 0.36 muB for x = 34.4 to 0.20 muB for x = 47.9. The magnetism revealed at V atoms is linearly correlated with the magnetic moment of Fe atoms, which implies that the former is induced by the latter.

Ce valence in intermetallic compounds by means of XANES spectroscopy

The cerium effective valence was investigated by means of CeL 3 -XANES spectroscopy in some intermediate valence Ce-based systems with different magnetic ordering mechanisms: CeNi doped with Nd, Pr and Gd in the temperature range 5-300 K, and Ce 2 Fe 17-x Mn x intermetallics. The dependences obtained are considered within the frames of generally accepted mechanisms of rare-earth ions intermediate valence states. Possible correlations between the cerium effective valence and the magnetic properties of compounds are also noted.

Structure, Morphology and Magnetization of Fe-Pd Thin Films

Several Fe(100-x)Pd(x0 thin films with x = 24-35 have been investigated to understand their structural, morphological and magnetic properties. The lattice spacing d111 obtained from the X-ray diffraction peaks shows a gradual increase with increasing x and this behaviour is attributed to the increasing substitution of Pd with larger atomic radius. While the atomic force microscopy images on selected samples showed surface roughness in the range 2-4 nm the scanning electron microscopy image of a Fe71Pd29 sample showed slightly dark and bright regions due to the large undulations of the surface of the films. We presume that these undulations are due to shape memory twin variants. In-plane magnetization measurements were carried out on selected films in applied magnetic fields up to 30 kOe. For three samples, the saturation magnetization is about 1300 emu/cc whereas for the Fe71Pd29 film it is about 950 emu/cc. The remanence ratio of the films is approximately in the range 50-70%. The behaviour of coercivity of our samples is believed to be due to grain size effect that generally plays a predominant role in thin films with nanometer size grains.

Microstructural Evolution during Post Deposition Annealing of Pulsed Laser Deposited Fe(100-x) Pdx Thin Films

AbstractFePd belongs to a group of L10 - intermetallics with attractive uniaxial hard-ferromagnetic properties. In this study thin films of different composition FeXPd1-X, X= 50, 60, were deposited by pulsed laser deposition (PLD) on amorphous SiO2 and Si3N4. We characterized the microstructural evolution during the different order/disorder phase-transformations during post-deposition annealing relative to the as-deposited state in terms of morphology, grain size, texture and presence of short-range order using SEM, XRD and TEM. VSM measurements were used to monitor magnetic properties. Differences in these microstructural parameters are due to different ordering reactions FCC to L10 ordering and concomitant phase separation of ?-Fe vs. FCC to L10 ordering upon heat treatment. The relationships of the different phase transformation products to properties are discussed. Support from NSF-DMR-Metals is gratefully acknowledged.

Phase Composition and Structure of the Fe(100-x)C(x); x=5-25 at.% Powders after Mechanical Alloying and Annealing

Phase Composition and Structure of the Fe(100-x)C(x); x=5-25 at.% Powders after Mechanical Alloying and Annealing

Magnetic field induced phase transition in Ce 2 Fe 17-x Mn x compounds

The atomic and magnetic structures of Ce2Fe17−xMnx compounds with x = 0.5 and 1.0 were inves- tigated using neutron diffraction under magnetic fields up to 5.0 T over the temperature range 2 − 300 K. The magnetic reflexes observed at temperatures 2 − 208 K and µ0 H = 0T correspond to an incommensurate antiferromagnetic struc- ture with wave vector (0, 0, 0 ± τ) at 2 K. This structure is suppressed in an external magnetic field and a ferromagnetic phase is induced in fields higher than 0.6 T. The complex transformation of the magnetic structures under magnetic field and temperature is analyzed and discussed. 1 Experimental methods Polycrystalline samples of Ce2Fe17−x Mnx with x = 0. 5a nd 1.0 were prepared by high-frequency melting under argon at- mosphere in Al2O3 crucibles. The ingots were annealed under vacuum at 1173 K for 3 days and then quenched in water. X-ray diffraction at room temperature with CuKα radiation was employed to test the structure and the lattice parame- ters. Neutron-diffraction experiments were performed at the high-flux reactor of the ILL. The high-resolution D2B and D1A powder diffractometers were used for a detailed study of the crystal structure at selected temperatures. The high- intensity powder diffractometer D1B was used for thermal scans under magnetic fields up to 1.2 T using a wavelength of 2.524 A and covering an angular range from 2 up to 82 degrees in 2Θ. In all cases the neutron diffraction data refine- ment was performed using the Rietveld method by means of the FULLPROF program.

Effect of pressure and Mn substitution on magnetic ordering of Ce 2 Fe 17-x Mn x ( x=0,1 )

The magnetic ordering of Ce2Fe17 and Ce2Fe16Mn at ambient and under high pressures up to 5 kbar was studied by neutron diffraction in the temperature range 2–300 K. The existence of collinear ferromagnetic (below 94 K) and incommensurate helical antiferromagnetic structures with a propagation vector τ1=(0,0,τ1z) was found at ambient pressure in Ce2Fe17. A helical structure with τ2=(0,0,τ2z) exists below 200 K down to low temperatures in Ce2Fe16Mn. Application of pressure results in the suppression of the ferromagnetic phase in Ce2Fe17 by P>3 kbar. A new pressure-induced incommensurate antiferromagnetic phase appears at T 3 kbarit transforms to a non-collinear phase, which can be described using a distorted elliptical spiral model.

Magnetic Phase Diagram of Amorphous Fe100?xScx Alloys

An overview will be given on the magnetic properties of amorphous Fe 100-x Sc x alloys. The experimental magnetic phase diagram in an external field of 100 Oe is established on amorphous films that were prepared in ultra high vacuum. At x 41, Sc atoms carry magnetic moments which couple antiferromagnetically to the Fe-atoms. Because of the complexity of the exchange interaction in the present system, antiferromagnetic as well as ferromagnetic and (reentrant) spin glass ordering was observed. Above x > 80, there are indications of superconductivity below 11 K.

Formation of Supersaturated Single-phase bcc Solid Solutions in Fe-Zn Binary System by Mechanical Alloying

Mechanical alloying (MA) was used in the investigation of the Fe-Zn binary system, which, in the equilibrium state, exhibits negligible mutual solid solubility at room temperature. The formation of single-phase bcc solid solutions with a nanometer-scaled microstructure was achieved by MA in Fe 100-x Zn x (x < 65) powder mixtures. The nearest neighbor distances of these Fe-Zn solid solutions obey the linear relationship given by the Vegard's law for ideal solutions, suggesting that the solid solutions formed by MA are homogeneous. The average lattice volume expansion also linearly increases to about 13.4% at 65%Zn. At elevated temperatures the nanostructured solid solutions undergo phase transformations yielding intermetallic compounds. The mechanisms for the phase formation in the Fe-Zn system are discussed.

HALL EFFECT IN DIFFERENT MAGNETIC PHASES OF Fe-RICH γ-FeNiCr ALLOYS

In this paper we present the Hall effect data of Fe 80-x Ni x Cr 20(14≤x≤30) alloys in four different magnetic phases within the fcc γ-phase. In the spin-glass (SG) phase (x=19) the nonlinear behaviour of the Hall resistivity (ρ H ) with field arises from the spin-orbit scattering. The temperature variation of ρ H shows broad peaks around T g for lower fields (&lt;0.1 T) but they disappear at higher fields (1 T). We separate the ordinary (OHC) and the extra-ordinary (EHC) Hall coefficients in the ferromagnetic sample (x=30) and show their temperature variation. In the reentrant spin-glass (RSG) (x=26), again ρ H shows a nonlinear variation with field. The temperature variation of ρ H shows anomaly near both T g and T c . In the antiferromagnetic phase (AF) (x=14), ρ H increases more or less linearly with field and its temperature variation shows broad peaks around T N for lower fields.

Structural and Magnetic Properties of Sm2Fe17?xMnxNy with 0 ? x ? 6 and y ? 3

The crystallographic and magnetic properties of the pseudo-binary Sm 2 Fe 17-x Mn x solid solution and its nitride, have been extensively studied. Mn substitution of Fe does not change the structure of Sm 2 Fe 17 . The substitution of iron by manganese decreases the parameters a, c and the unit-cell volume in the range of 0 ≤ x ≤ 2, then it increases. The Curie temperature and the saturation magnetisation decrease with increasing Mn content. The easy magnetisation direction is perpendicular to the c-axis in the region x < 2, and after it changes into parallel to the c-axis. The insertion of nitrogen in the substituted compounds increases the crystallographic and magnetic properties. The parameter a of the nitride alloys decreases with Mn content for 0 < x < 2, then it increases. However, the parameter c of all the nitrides increases with increasing Mn content. The Curie temperature and the saturation magnetisation decrease with increasing Mn concentration. Finally, all the nitrides exhibit an easy magnetisation direction parallel to the c-axis.

The microstructure and magnetic properties of nanocrystalline Fe 100-x Si x alloys

Nanocrystalline Fe100-xSix (x≤25) alloys have been prepared by mechanical alloying. The crystallite size of the nanocrystalline FeSi alloys is about ten to fifteen nm. The individual crystallite separated by disordered grain boundaries has the structure of b.c.c. α-Fe. The Mossbauer patterns show that substitution of Si atoms for Fe ones is almost disordered in the nanocrystalline FeSi alloys. The saturation magnetization of the nanocrystalline FeSi alloys is slightly less than that of single-crystalline and polycrystalline FeSi alloys, whereas their coercive force and effective magnetocrystalline anisotropy constant are higher than those of the corresponding single-crystalline and polycrystalline FeSi alloys. The much higher coercive force and higher effective anisotropy of the nanocrystalline FeSi alloys may be related to the high strain in the grain boundaries.

Magnetic Properties of Mechanically Alloyed Sm2Fe17—xGaxCy

Alloys of Sm 2 Fe 17-x Ga x C y have been prepared by mechanical alloying, and their magnetic properties have been determined. High coercivities of 15 to 16 kOe were found in samples with Ga concentrations of 1.5 to 2. The Sm 2 Fe 15.5 Ga 1.5 C alloy had a remanence of 65 emu/g and a maximum energy- product of 10 MGOe using the theoretical density. Study of irreversible magnetization and viscosity exhibited behavior similar to that found in other rare-earth permanent magnets with fine-crystalline structure.

Magnetic phase transitions in Fe 80-x Ni x Cr 20 (14 ⩽ x ⩽ 30) alloy studied by using 57 Fe Mössbauer spectroscopy

This paper reports 57Fe Mossbauer spectroscopic studies of the polycrystalline samples of the substitutionally disordered, isostructural (fcc), ternary alloy system Fe80-xNixCr20 for x = 30, 26, 19 and 14 in the temperature range of 10–295 K. The data have been analyzed in terms of the magnetic phase transitions occurring in these alloys by examining the temperature dependence of the various Mossbauer parameters like line‐width, center shift, resonance area, distribution of hyperfine field, P(H), and the average hyperfine field 〈H〉. An estimate of the magnetic transition temperature TC is made for the alloys with x = 30 and 26 and these results are compared with those previously obtained by magnetic measurements and neutron diffraction experiments. The data for the second order Doppler shift have been analyzed to estimate the Debye temperature ΘD for alloys with x = 30 and 26.

Influence of Fe2+ on microwave behaviour of M(Co, Ti)l,2 type hexaferrite

This work deals with M-type Co,Ti substituted barium hexaferrite, Ba(CoTi) x Fe 12-2x O 19 studied near the uniaxial-planar transition (x≥1,2). A single crystal state like was obtained by using textured ceramic. Our aim is to observe the effect of the divalent iron ions on the permeability curves. We have correlated the presence of Fe 2+ ions with the variation of the value of the permittivity e' at 0.1 GHz. The concentration of Fe 2+ ions has been varied by annealing the sintered materials under either reducing (N 2 ) or oxidizing (O 2 ) atmosphere. We have tried to interprete the important variations of the permeability in terms of domain wall and gyromagnetic contributions.

Specific natural ferromagnetic resonance in amorphous microwires covered by glass insulation

UHF and static magnetic properties of (Fe 100-x C x ) 87 B 4 Si 5 Mn 4 microwire for X values from 10 to 20% are studied. Microwires made of such compositions may be both in amorphous or crystalline states and have a mixed structure leading to the broadening of Natural Ferromagnetic Resonance (NFMR) lines and occurrence of resonance at several adjacent frequencies. Static histeresis loops in such microwires are characterised by the presence of several large Barkhausen jumps wich points to inhomogeneous phase and magnetic structure.

Phase Stabilities and Magnetic Properties of Fe-Cu Solid Solution Prepared by Mechanical Alloying

Fe 100-X Cu X solid solutions with X = 5, 10, 15, 20 have been obtained by mechanical alloying of elemental Fe and Cu powders. The structure and the atomic configuration of these solutions have been studied by X-ray diffraction and 57 Fe Mossbauer spectroscopy. X-ray diffractions showed that bcc Fe(Cu) solutions were formed after 15, 20 and 30 hours milling respectively. Mossbauer spectra were composed of 3 or 4 magnetically splitted sextets. Each hyperfine fields were (A) 327-329 kG, (B) 316-318 kG, (C) 302-304 kG, (D) 284 kG. These components correspond to (A) Fe atoms surrounded with 8 Fe, (B) Fe with 1 Cu + 7 Fe, (C) Fe with 2 Cu + 6 Fe, (D) Fe with 3 Cu + 5 Fe in bcc lattice. Mossbauer spectra for Fe-Cu solutions could be considers by the distribution change of these components with Cu concentrations.

The Role of the Nature of Magnetic Coupling on the Martensitic Transformation in Fe-Ni

Fe 100-x Ni x with x ≤30 at.%, known as anti-Invar alloys, undergo martensitic transformations. Total energy calculations have shown that these alloys incorporate a strongly fluctuating magnetic moment in the fcc state. In order to understand the relationship between the moment fluctuations and the martensitic transformation, we have investigated the magnetic moment in the paramagnetic fcc state of these alloys by polarized neutron diffraction. We find that the magnetic correlations are ferrornsgtic in nature although, the ground state of these alloys are expected to be antiferromagnetic. We fwker observe that the magnetic moment of the fcc state at M, increases with increasing Ni concentration, indicating that the fcc state is stabilized by increasing ferromagnetic exchange. The results are found to be in agreement with thermodynamical predictions.

Dielectric Behavior in BaCO2xFe\boldmath12-2xO19

The real dielectric constant e' and loss factor tan δ were studied as function of frequency f, temperature T and composition x for a series of samples of BaCo 2x Zn x Fe 12-2x O 19 hexagonal ferrite system with x = 0.4, 0.8, 1.2, 1.6 and 2 prepared using the usual ceramic technique. The experimental results indicated that e' and tan δ decrease as the frequency increases and temperature decreases. The studied samples showed abnormal dielectric behavior (or relaxation peaks) which were shifted towards higher frequency as the temperature and substitution of Co and Zn ions increase. Increasing the Co and Zn ions substitution for x ≤ 1.2, e' and tan δ decrease reaching minima while activation energy for dielectric relaxation E D and pre-exponential constant f 0 increase reaching maxima at x = 1.2. The behavior was reversed for x > 1.2, where e' and tan δ increase while E D and f 0 decrease.