Search

Fe/Al multilayer thin films with an overall atomic concentration ratio of Fe:Al=1:2 have been prepared by ion-beam sputtering. Phase formation and microstructural evolution with thermal annealing have been studied by x-ray reflectivity, cross-sectional transmission electron microscopy, dc magnetization, and conversion electron Mössbauer spectroscopy. These studies show that although the starting composition is Al rich, the intermixing of Fe and Al at the interfaces leads to the formation of a magnetic Fe3Al-like region at the interface. Thus, the magnetic contribution in the as-deposited multilayer structure (MLS) is not only from pure Fe but also from an Fe3Al-like region formed at the interface. On annealing the MLS, a stable nonmagnetic MLS consisting of intermetallic B2 Fe50Al50 separated by thin Al layers is formed. Further annealing only induces better ordering of Fe50Al50 and does not destroy the MLS. [ABSTRACT FROM AUTHOR]

A study is conducted to examine the structural evolution and microscopic and bulk magnetic properties of Fe/Al multilayer thin films with an overall atomic concentration ratio of Fe:Al = 1:2 prepared by ion-beam sputtering. The as-deposited multilayer structure (MLS) is influenced by the Fe and [Fe.sub.3]Al-like region formed at the interface.

Single phase MFeCrO4 (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO4 and NiCrFeO4 samples are 8.374 and 8.325 Å and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm−1, indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO4 having a higher value of saturation magnetisation. Mössbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe3+ cations is higher in NiCrFeO4. [ABSTRACT FROM AUTHOR]

Fe/Al multilayer thin films prepared by ion beam sputtering, with an overall atomic concentration ratio of Fe/Al = 1:2 have been studied by x-ray diffraction spectroscopy (XRD), X-ray reflectivity (XRR) and D.C. Magnetization. These studies show the formation of Fe–Al intermetallic layers. Two magnetic regions and transition temperatures of 473 and 533 K are evident from magnetization studies. Conversion Electron Mössbauer Spectroscopy (CEMS) shows formation of off-stoichiometric Fe3Al like phase and phases consisting of pure Fe and Fe-rich extended Fe–Al solutions. [ABSTRACT FROM AUTHOR]

Nanostructured Fe2CrAl has been prepared by mechanical alloying using a high energy ball mill. The structural and magnetic properties of the as-milled and mechanically alloyed sample annealed in the presence of a magnetic field have been studied by means of X-ray diffractometry, 57Fe Mössbauer spectroscopy and DC magnetization. The observed properties are compared to that of the bulk sample. The magnetic hyperfine fields are related to structural disorder. There is a very good enhancement of bulk magnetic properties in the nano-sized samples, the most notable one being a dramatic increase in the Curie temperature of these samples and are explained in terms of structural disordering and size effect. [ABSTRACT FROM AUTHOR]

Abstract: Structural and magnetic properties of Fe100 − x Al x powders, mechanically alloyed for a fixed time of 10 h, is presented. Although Mössbauer studies show that the magnetic phase is a minimum, bulk magnetic properties like area of the M–H loop and coercivity are maximum in the Al-rich x =66 (Fe–66 at.% Al) system. Quadrupole splitting and isomer shift of the non-magnetic phase in this system are identical to that of stoichiometric FeAl2. The unexpected trend of the bulk magnetic parameters in the x =66 composition is explained in terms of the enhanced intergranular exchange coupling, mediated by the Fe atoms in the non-magnetic phase. [Copyright &y& Elsevier]

Mechanically alloyed Fe100 − x Al x powders, with 20≤ x ≤90, have been studied by X-ray diffraction and room temperature 57Fe Mössbauer spectroscopy. The milling time was chosen such that complete alloying does not take place. For a fixed milling time of 10 h, the rate of alloying was seen to increase exponentially with increase in Fe content. Mössbauer spectra of all the samples consist of a broad magnetic sextet and a quadrupole doublet. The isomer shifts and quadrupole splitting of the doublets are typical of Al-rich, Fe–Al alloys. The area under the quadrupole doublet is a maximum for x = 66. Analysis of the Mössbauer spectra indicates the formation off- stoichiometric Fe3Al phase for x < 66, while the formation of Fe clusters is largely responsible for the magnetic hyperfine component in x ≥ 66 compositions. [ABSTRACT FROM AUTHOR]