Magnetic properties of ball milled Fe-40 Al at.% alloys

Amils, X.; Nogués, J.; Suriñach, Santiago; Baró, Maria Dolores; Muñoz, J.S.

doi:10.1109/20.706409

Cited by 41 publications

(29 citation statements)

References 9 publications

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“…As an example we can mention that x-ray diffraction of ball milled alloy of composition Fe 60 Al 40 shows an increase of the lattice parameter with milling time (7). This lattice parameter increase has been assumed to produce a variation of the density of states at the Fermi level that would cause the magnetic transition (8).…”

Section: Palabras Clave: Aleaciones Fe-al Código Tb-lmto Transformamentioning

confidence: 99%

Propiedades electrónicas y magnéticas de las aleaciones Fe-Al

Apiñaniz¹,

Plazaola²

2000

Bol. Soc. Esp. Ceram. Vidr.

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This work presents ab-initio self-consistent calculations performed with the TB-LMTO code to study the different phases of the Fe-Al phase diagram, corresponding to the ordered structures B2, DO3 and B32 and for Fe 50 Al 50 and Fe 3 Al compositions. Both, unpolarized and spin-polarized calculations have been performed to deduce the energetic difference between the paramagnetic and ferromagnetic state of the corresponding structure. Calculations for the disordered structures have also been performed for the previously mentioned compositions. These results show that by disordering the alloy magnetism is enhanced and that the equilibrium lattice parameter increases. Keywords: Fe-Al alloys, TB-LMTO code, magnetic transformations, order-disorder. Propiedades electrónicas y magnéticas de las aleaciones Fe-AlEn este trabajo se presentan cálculos autoconsistentes ab-initio realizados con el método TB-LMTO (Tight Binding Linear Muffin Tin Orbital) con el fin de estudiar las diferentes estructuras que se presentan en el diagrama de fases de las aleaciones Fe-Al. Se han estudiado las estructuras ordenadas B2, DO3 y B32 para las siguientes concentraciones: Fe50Al50 y Fe3Al. Asimismo, se han realizado cálculos teniendo y sin tener en cuenta la polarización de spin con el fin de poder deducir la diferencia energética entre los estados ferromágneticos y paramágneticos de la misma estructura. Por otra parte se han realizado estos mismos cálculos para estructuras desordenadas y las mismas concentraciones. Los resultados muestran que mediante el desorden aumenta el magnetismo de estas aleaciones y crece el parámetro de red. Palabras clave: Aleaciones Fe-Al, código TB-LMTO, transformaciones magnéticas, orden-desorden.room temperature), B32 long range order was observed by Becker and Schweike in neutron scattering experiments (4). Calculations of model alloys show that the B32 phase has a tendency to exist at even larger deviations from stoichiometry than the B2 phase.It has been shown that these alloys are of the ferromagnetic disordered type (BCC, A2) for Al concentrations up to 23 at % Al independent of heat treatment (5). In alloys with Al content ranging from 0 to 30 at % the iron atoms carry their normal magnetic moment of 2.2 µ B when they have at least five or more iron atoms as nearest neighbours (6). The 30 at % Al composition is critical for these systems were the average magnetic moment per Fe atom decreases rapidly from 2.0 to 0.7 µ B ; coupled with this there is a large fall in the lattice parameter associated with a fall in the atomic radii as the disorder to order transition occurs (20 to 30 at % Al).By disordering the alloy paramagnetic-ferromagnetic transitions can be induced and these transitions could be related to the changes in volume and not only to nearest neighbour effects as is commonly assumed. As an example we can mention that x-ray diffraction of ball milled alloy of composition Fe 60 Al 40 shows an increase of the lattice parameter with milling time (7). This lattice parameter increase has been assumed...

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Section: Palabras Clave: Aleaciones Fe-al Código Tb-lmto Transformamentioning

confidence: 99%

Propiedades electrónicas y magnéticas de las aleaciones Fe-Al

Apiñaniz¹,

Plazaola²

2000

Bol. Soc. Esp. Ceram. Vidr.

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“…Similar correlations between induced ferromagnetism and structural disorder were reported in Fe 60 Al 40 subject to mechanical deformation experiments. Namely, an increase of the saturation magnetization was observed in Fe 60 Al 40 powders during ball milling 31 and in bulk Fe 60 Al 40 alloy under application of macroscopic compressive stress. 32,33 Contrary to the saturation magnetization, the coercivity, H C , does not depend in a simple and monotonic manner on the amount of structural disorder.…”

Section: Resultsmentioning

confidence: 99%

“…Three dimensional magnetic structures with an oblate spheroidal hemisphere shape with 350 nm in diameter were represented using 2.5 Â 2. the most and less irradiated samples, respectively. 31 For the exchange parameter A a value of 1 lerg/cm 3 was used. The simulations were carried out using two different values for the anisotropy, 10 3 and $10 5 erg/cm 3 .…”

Section: Methodsmentioning

confidence: 99%

“…5(c) and 5(d)], provided the net anisotropy is weak and assuming values for the saturation magnetization similar to those previously reported in the literature. 31 The less irradiated samples, however, are expected to maintain single domain configurations. The relatively low values of K are probably realistic since the random directions of the induced structural disorder will have the net effect of lowering the value of the effective magnetic anisotropy.…”

Section: -3mentioning

confidence: 99%

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Tuneable magnetic patterning of paramagnetic Fe60Al40 (at. %) by consecutive ion irradiation through pre-lithographed shadow masks

Varea

Menéndez

Montserrat

et al. 2011

Journal of Applied Physics

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Arrays of ferromagnetic circular dots (with diameters ranging from 225 to 420 nm) have been prepared at the surface of atomically ordered paramagnetic Fe 60 Al 40 (at. %) sheets by means of ion irradiation through prelithographed poly(methyl methacrylate) (PMMA) masks. The cumulative effects of consecutive ion irradiation (using Ar þ ions at 1.2 Â 10 14 ions/cm 2 with 10, 13, 16, 19 and 22 keV incident energies) on the properties of the patterned dots have been investigated. A progressive increase in the overall magneto-optical Kerr signal is observed for increasingly larger irradiation energies, an effect which is ascribed to accumulation of atomic disorder. Conversely, the coercivity, H C , shows a maximum after irradiating at 16-19 keV and it decreases for larger irradiation energies. Such a decrease in H C is ascribed to the formation of vortex states during magnetization reversal, in agreement with results obtained from micromagnetic simulations. At the same time, the PMMA layer, with an initial thickness of 90 nm, becomes progressively thinned during the successive irradiation processes. After irradiation at 22 keV, the remaining PMMA layer is too thin to stop the incoming ions and, consequently, ferromagnetism starts to be generated underneath the nominally masked areas. These experimental results are in agreement with calculations using the Monte-Carlo simulation Stopping Range of Ions in Matter software, which show that for exceedingly thin PMMA layers Ar þ ions can reach the Fe 60 Al 40 layer despite the presence of the mask.

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“…This increase of the magnetism has been explained in terms of the change of the local environment [2,3] where mechanical deformation destroys the intermetallic order in heavily deformed alloys. Furthermore, mechanical deformation causes an increase in volume [4,5] and the influence of the Fe-Fe interatomic distance on the magnetic moment has been proven both theoretically and experimentally in a few studies [6][7][8]. Therefore, in order to explain this behaviour the relationship between microstructure and magnetism has to be taken into account, indeed, this is linked to the fact that the Fe-rich side of Fe-Al phase diagram presents three main phases: ordered D0 3 and B2, and disordered A2.…”

Section: Introductionmentioning

confidence: 99%

Study of the structure influence on the magnetism of Fe₇₀Al_30-xSi_xalloys

Legarra

Apiñaniz

Plazaola

2014

EPJ Web of Conferences

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Abstract. The influence of the different structures on the evolution of the magnetism in the order-disorder transition produced by mechanical milling in the intermetallic Fe 70 Al 30-x Si x alloys has been systematically studied by means of XRD measurements, Mössbauer spectroscopy and magnetic measurements. These techniques show that there are two different stages in the evolution of the magnetism during the order-disorder transition and both stages are related to the presence of ordered B2 in annealed alloys. In a first stage the magnetization of the alloys decreases and this decrease corresponds to the presence of B2 structure and the disordering of the D0 3 structure. In the second stage the magnetization increases corresponding to the disordering of the B2 structure. Therefore, the increase of the magnetization is related to the disordering of B2 structure, but not to the disordering of D0 3 structure. Besides, when plotting the normalized variation of magnetization produced by the disorder versus the normalized variation of lattice parameter we observe a linear relationship, showing that lattice parameter and magnetic properties are also related.

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Magnetic properties of ball milled Fe-40 Al at.% alloys

Cited by 41 publications

References 9 publications

Propiedades electrónicas y magnéticas de las aleaciones Fe-Al

Propiedades electrónicas y magnéticas de las aleaciones Fe-Al

Tuneable magnetic patterning of paramagnetic Fe60Al40 (at. %) by consecutive ion irradiation through pre-lithographed shadow masks

Study of the structure influence on the magnetism of Fe₇₀Al_30-xSi_xalloys

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Magnetic properties of ball milled Fe-40 Al at.% alloys

Cited by 41 publications

References 9 publications

Propiedades electrónicas y magnéticas de las aleaciones Fe-Al

Propiedades electrónicas y magnéticas de las aleaciones Fe-Al

Tuneable magnetic patterning of paramagnetic Fe60Al40 (at. %) by consecutive ion irradiation through pre-lithographed shadow masks

Study of the structure influence on the magnetism of Fe70Al30-xSixalloys

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Study of the structure influence on the magnetism of Fe₇₀Al_30-xSi_xalloys