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We have studied the first-order magnetic phase transition and related physical properties of MnFeP[SUB0.5]As[SUB0.4]Si[SUB0.1] by means of x-ray diffraction, magnetization, thermal expansion, and electrical resistance measurements. The compound crystallizes in the hexagonal structure with Fe[SUB2]P-type. The temperature dependence of magnetization shows a first-order magnetic phase transition around 299 K. There is no crystallographic structural transition associated with the magnetic phase transition. The linear thermal expansion shows that this magnetic phase transition is accompanied by a negative volume change. The electrical resistance shows an anomalous behavior at the transition, which is probably caused by the change in c/a ratio. [ABSTRACT FROM AUTHOR]

Abstract: The structural and magnetic properties of MnCo1−x V x Ge (x =0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20 and 0.30) compounds were investigated by means of X-ray diffraction, scanning electron microscopy and magnetization measurements. The MnCo1−x V x Ge compounds crystallize in the orthorhombic TiNiSi-type crystal structure for x ≤0.02 and in the hexagonal Ni2In-type structure for x >0.02. The magnetization measurements show that the MnCo1−x V x Ge compounds exhibit a complex magnetic behavior. The Curie temperature can be tuned from 360K to 148K by increasing x. The maximal magnetic-entropy change is 3.9J/kgK for x =0.06 at a field change from 0 to 1.5T at about 265K. [Copyright &y& Elsevier]

Abstract: We have performed powder X-ray-diffraction measurements on in fields up to 5T in the temperature range 8–310K. The compound which has the hexagonal type of structure shows a field-induced isostructural phase transition. We found that the cell volume decreases slightly and continuously with increasing magnetic field, although the lattice parameter ratio c/a drastically changes. A tentative analysis of the dependence of the lattice parameters on the magnetization has been carried out using the extended Bean–Rodbell model. [Copyright &y& Elsevier]

The structural and magnetic properties of MnFe1-xCox Ge compounds with x = 0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.85,0.9, and 1.0 were investigated by means of X-ray diffraction (XRD) and magnetization measurements. XRD shows that the MnFe1-x Cox Ge compounds crystallize in the hexagonal Ni2In-type crystal structure for x ≤ 0.8 and in the orthorhombic NiTiSi-type structure for x > 0.8. The magnetization measurements show that the MnFe1-x Cox Ge compounds exhibit a complex magnetic behavior. The Curie temperature increases with increasing of x. The saturation magnetization of the compounds with Ni2In type structure increase with increasing of x and the saturation of the magnetization in the NiTiSi-type structure also increases with increasing x. We investigated the magnetocaloric effects in these compounds by means of magnetization measurements. The maximum magnetic-entropy change observed in these compounds reaches 9 J/kgK for x = 0.8 in a field change from 0 to 5 T at around 289 K. [ABSTRACT FROM AUTHOR]

Provides information on a study that examined the magnetic properties of the compound, HoTiGe by means of magnetization measurements at different temperatures and fields. Experimental details; Results and discussion on the study.

One important aspect of the magneto-structural transition in MnCoGe-based materials is the reduction in saturation magnetization from the orthorhombic to the hexagonal phase. Here, by combining an element specific magnetization probe such as x-ray magnetic circular dichroism and band structure calculations, we show that the magnetic moment instability between orthorhombic and hexagonal structures originates from a reduction in the Mn sub-lattice magnetization. [ABSTRACT FROM AUTHOR]

Abstract: We report on magnetic properties and magnetocaloric effects of Mn5Ge3−x Si x alloys with x =0.1, 0.3, 0.5, 1.0, 1.5 and 2.0. All Mn5Ge3−x Si x compounds crystallize in the Mn5Si3–type hexagonal structure with space group P63/mcm. The lattice parameters and the Curie temperature of Mn5Ge3−x Si x alloys decrease with increasing x. A considerable large magnetic-entropy change has been observed in these alloys near room temperature. Typical values are 2.3 and 7.8J/kgK at T c =299K for magnetic field changes from 0 to 1T and from 0 to 5T, respectively. The average Mn magnetic moment decreases with increasing Si content. The substitution of Si in Mn5Ge3 does not result in a change of the crystal structure. But the Si substitution has two kinds of effects on the magnetocaloric effects. One is that the magnetic-entropy change decreases with increasing Si content, the other one is that the magnetocaloric effect peak becomes broadened. [Copyright &y& Elsevier]

Abstract: The phase formation and the magnetic properties of YFe12− x Nb x compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that all compounds investigated crystallize single phase in the tetragonal ThMn12-type of structure. The lattice parameters and the unit-cell volume increase slightly with increasing Nb content, but the Curie temperature does not change. The X-ray-diffraction patterns of aligned powders of the samples show that all the compounds investigated have uniaxial anisotropy at room temperature. At 1.5K, the spontaneous magnetization, the anisotropy field and the anisotropy constant K 1 decrease with increasing Nb content. [Copyright &y& Elsevier]

We explore the crystal structure and magnetic properties of quaternary materials deriving from the hexagonal Fe 2 P, an iron binary known to present a particularly large magnetocrystalline anisotropy potentially interesting for permanent magnets, but with unfortunately a Curie temperature far too low for applications. Using simultaneous metal and metalloid substitutions in Fe 2- z Co z P 1- x B x and Fe 2- z Co z P 1- y Si y quaternaries, we found it is possible to increase the Curie temperature up to at least 640 K while maintaining a c axis uniaxial magnetocrystalline anisotropy, leading to an appreciable magnetic anisotropy at room temperature. In Fe 2-z Co z P 1- x B x , though boron is appropriate to increase the Curie temperature, its amount is limited as it also favors the formation of secondary phases. Contrary to what could be anticipated from the phase diagrams of Fe 2- z Co z P or Fe 2 P 1- y Si y ternaries, simultaneous Co for Fe and Si for P substitutions in Fe 2- z Co z P 1- y Si y are found to significantly expand the range of stability of the Fe 2 P-type crystal structure. X-ray diffraction patterns on powders oriented in magnetic field indicate a c axis uniaxial magnetic anisotropy. Appropriate heat-treatments and slight metal deficiency are found suitable to limit the formation of unwanted secondary phase with 3:1 metal:metalloid ratio. As a result, nearly single-phase Fe 1.95- z Co z P 1- y Si y materials are prepared and exhibit an appreciable magnetic anisotropy with K 1 up to approximately 0.93 MJm−3 at room temperature. This study experimentally demonstrates that Fe 2 P-type transition metal quaternaries can present an interest not only for their first-order magnetic transition, but also for their magnetic anisotropy making them potential candidates for magnetostatic applications. Image 1 • A sizable magnetic anisotropy is obtained in Fe 2 P-quaternaries at room temperature. • Phase diagrams and structure-properties relations of Fe 2 P-quaternaries are explored. • Fe 2- z Co z P 1- y Si y alloys preserve an Fe 2 P-type crystal structure up to y ∼0.6. • Fe 2- z Co z P 1- y Si y alloys present high Curie temperature and uniaxial anisotropy. • Fe 1.8 Co 0.2 P 1- x B x alloys are synthesized, but B content is limited to x ∼0.12 [ABSTRACT FROM AUTHOR]

We have obtained single-phase compounds Gd[SUB3]Fe[SUB29-x-y]Co[SUBx]Cr[SUBy] with the Nd[SUB3] (Fe,Ti)[SUB29]-type. Cr is a stabilizing element and also increases the solid-solution limit of Co in the Gd[SUB3]Fe[SUB29-x-y]Co[SUBx]Cr[SUBy] compounds. Substitution of Co by Fe results in a significant change of the magnetocrystalline anisotropy and changes the easy magnetization direction from basal-plane to easy-axis when x > 10 and y = 4. The intensity of the magnetic interactions in Co-rich Gd[SUB3]Fe[SUB29-x-y]Co[SUBx]Cr[SUBy] compounds has been calculated from the high-field magnetization measurements. The Co substitution suppresses the Invar anomaly found in the Gd[SUB3](FeCr[SUB29] compounds. [ABSTRACT FROM AUTHOR]

Examines magnetocrystalline anisotropy, Curie temperatures, spin reorientation temperatures and first order magnetization process for heavy rare-earth iron silicon compounds. Standard measurements of the initial susceptibility; Information regarding the magnetic interaction strengths; Use of x-ray diffraction patterns.

The present work is devoted to fabrication of Fe–B–Si–Zr multi-component bulk glassy alloys with good mechanical and soft magnetic properties. Glass formation in Fe–B system is first considered with an empirical cluster-plus-glue-atom model. A basic composition formula [B–B 2 Fe 8 ]Fe is proposed as the framework for multi-component alloy design. Considering the structural stability of the model glass, Si and Zr are introduced to the [B–B 2 Fe 8 ] cluster to replace the center B and shell Fe atoms, from which a series of Fe–B–Si–Zr alloys with composition formulas [Si–B 2 Fe 8−x Zr x ]Fe (x = 0–0.6) are derived. Copper mold casting experiment shows that bulk glassy alloys are formed within the Zr content range of x = 0.2–0.6, and the largest glass-forming ability appears at [Si–B 2 Fe 7.6 Zr 0.4 ]Fe with a critical size of 2.5 mm. The bulk glassy alloys exhibit high fracture strength as large as 3850 MPa. Magnetic property measurement indicates that these alloys exhibit good magnetic softness with high saturation magnetization (1.26–1.48 T) and low coercive force (1.6–6.7 A/m). The alloying effects of Si and Zr on bulk glass formation, thermal glass stability and magnetic softness are discussed with the empirical model. [ABSTRACT FROM AUTHOR]

Abstract: An accurate method to determine the magnetic entropy change in materials with hysteretic first-order transitions is presented, which is needed to estimate their potential for applications. We have investigated the effect of the maximal entropy change derived from magnetization measurements performed in different measurement processes. The results show that the isothermal entropy change can be derived from the Maxwell relations even for samples with large thermal hysteresis. In the temperature region with hysteresis, overestimating the entropy change can be avoided by measuring the isothermal magnetization of the sample after it is cooled from the paramagnetic state to the measurement temperature. In this way the so-called peak effect is not observed as shown here for a few compounds. [Copyright &y& Elsevier]

Abstract: The effects of substitution of Co for Fe on the magnetic and magnetocaloric properties of La0.8Ce0.2Fe11.4− x Co x Si1.6 (0, 0.2, 0.4, 0.6, 0.8 and 1.0) compounds have been investigated. X-ray diffraction shows that all compounds crystallize in the NaZn13-type structure. Magnetic measurements show that the Curie temperature (T C) can be tuned between 184 and 294K by changing the Co content from 0 to 1. A field-induced methamagnetic transition occurs in samples with x=0, 0.2 and 0.4. The magnetic entropy changes of the compounds have been determined from the isothermal magnetization measurements by using the Maxwell relation. [Copyright &y& Elsevier]

In this work, a novel method of producing maghemite (γ-Fe2O3) nanopowders has been developed, which can be performed by the direct thermal decomposition of an Fe–urea complex ([Fe(CON2H4)6](NO3)3) in a single step. The reaction mechanism, particle morphology, and the magnetic properties of the γ-Fe2O3 nanopowders have been studied by using thermogravimetric (TG), differential scanning calorimetry (DSC), fourier transformed infrared (FTIR) spectroscopy, elemental analysis, X-ray powder diffraction (XRD), transmission electron micrograph (TEM) observations, and magnetic measurements. Thermal analyses together with the results of XRD show that the formation of γ-Fe2O3 occurs at ~200 °C through a two-stage thermal decomposition of the [Fe(CON2H4)6](NO3)3 complex. The resulting iron oxide phases (i.e., γ-Fe2O3 and α-Fe2O3) are strongly dependent on the synthesis conditions of the [Fe(CON2H4)6](NO3)3. When the molar ratio of Fe(NO3)3 · 9H2O to CON2H4 that is used for the synthesis of [Fe(CON2H4)6](NO3)3 is 1:6 (i.e., molar ratio in stoichiometry), a mixed phase of γ-Fe2O3 and α-Fe2O3 is formed. When the molar ratio is 1:6.2 (i.e., using an excess CON2H4), on the other hand, a pure γ-Fe2O3 is obtained. Magnetic measurements show that resulting nanopowders exhibit a ferromagnetic characteristic and their maximum saturation magnetization increases from 47.2 to 67.4 emu/g with an increase in the molar ratio of Fe(NO3)3 · 9H2O to CON2H4 from 1:6 to 1:6.2. [ABSTRACT FROM AUTHOR]

Presents information on a study which determined the magnetic properties of a metallic compound comprised of dysprosium, iron and carbon. Analysis of the crystal structures of ternary carbides; Methodology of the study; Results and discussion.

Abstract: We have studied the magnetic properties and magnetic-entropy changes of the MnFeP0.5Ge0.5−x Si x compounds with x =0.1, 0.2, 0.3, 0.4 and 0.45. X-ray diffraction shows that the compounds crystallize in the Fe2P-type hexagonal structure. The lattice parameter a and the Curie temperature decreases with increasing x. The maximal magnetic-entropy changes for x =0.4 and 0.45 derived from the magnetization data are about 6.0J/kgK and 5.8J/kgK, respectively, for a field change from 0 to 1.5T. [Copyright &y& Elsevier]

Abstract: We studied the effect of hydrostatic pressure on the magnetic and magnetocaloric properties of the potential magnetic-refrigerant materials MnFeP1− x As x with x=0.35 and 0.55. While applied pressure reduces both the Curie temperature and magnetic moment of the former compound, the Curie temperature of the latter is increased whereas the moment is hardly affected by pressure. The same trends are seen in the magnetocaloric properties. These results indicate a different character of the magnetism in these two materials. While the compound with x=0.35 exhibits a volume instability like a weak itinerant ferromagnet, whereas the one with x=0.55 behaves as a strong itinerant ferromagnet. An alternative scenario may be formulated within the localized-moment picture. One may interpret the effect of pressure on the compound with x=0.35 as an indication of pressure-induced enhancement of antiferromagnetic interactions. This latter interpretation is offered by a pronounced enhancement of the high-field susceptibility under pressure. [Copyright &y& Elsevier]