Journal of Applied Mathematics and Physics, 2013, 1, 4-8 Published Online May 2013 (
Copyright © 2013 SciRes. JAMP
The Synthesis and Characterization of Arc Melted
Fe1xAlx Alloys
Sandeep Rajan1*, Rajni Shukla1, Anil Kumar2, Anupam Vyas2, Ranjeet Kumar Brajpuriya2
1Department of Physics, Deenbandhu Chhotu Ram University of Science & Technology, Sonipat, India
2Department of Physics, Amity University Haryana, Gurgaon, India
Email: *
Received May 10, 2013; revised June 11, 2013; accepted June 17, 2013
Copyright © 2013 Sandeep Rajan et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The paper presents correlation study on a series of Fe1xAlx alloy samples prepared by arc melting. All the samples
show crystalline structure, irrespective of the Al content and are textured mainly along (110) direction. The particle size
decreases rapidly with x particularly after x > 0.3. The corresponding magnetic measurements were obtained at room
temperature using a VSM, with a maximum applied field of 14 kOe. The results show that the ferromagnetic state of the
samples disappears with x, and becomes paramagnetic for alloys with x 0.4. It is also found that coercivity (Hc) and
resistivity increase with x. The results were interpreted in terms of continuous change in their electronic structure i.e.
overlap of the electron wave functions of the magnetic atoms with the Al electron wave function.
Keywords: Transition Metal Aluminides; Magnetization and Electronic Properties
1. Introduction
During the last decade, enormous progress has been
made in manufacturing and processing of materials with
intermetallic matrices [1]. Mechanical alloying (MA) [2],
which was initially conceived for the production of dis-
persion strengthened superalloys, is nowadays used for
synthesizing a wide range of materials including inter-
metallics [3]. A great advantage of mechanical alloying
(MA) process is the fact that it modifies the structure and
solid solubility limits of alloys and solid solutions and
induces lattice strains and phase transformations [4,5].
The formation of metastable phases and disordering of
the lattice through alloying gives rise to interesting me-
chanical and magnetic properties [6]. This is particularly
evident in the case of Fe-Al intermetallic systems. The
complicated phase diagram and the dependence of mag-
netic properties on the state of disorder and the micro-
structure [6,7] make this an interesting system to study
through the MA process. Both from the point of view of
understanding the collective behaviour of the magnetic
phases and also possible applications, study of such in-
termediate phases is expected to be very rewarding. As
FeAl intermetallic compound offers a combination of
several attractive properties such as a high specific
strength, good strength at intermediate temperatures and
an excellent corrosion resistance at elevated temperatures
under oxidizing, carburing and sulfidizing atmospheres
[8,9]. So they have attracted considerable attention as
potential candidates for structural and coatings applica-
tions at elevated temperatures in hostile environments
and as promising substitutes for stainless steels at room
temperature [10-13]. Due to these reasons, mechanically
alloyed [3-5] and mechanically milled [14] Fe-Al sys-
tems of various compositions have been investigated in
recent years. With this objective, the authors have suc-
cessfully synthesized FeAl intermetallics by MA and
systematically investigated the structural, magnetic and
electronic properties of a series of arc melted Fe1xAlx
(0.2 x 0.6) alloys using XRD, VSM and XPS.
2. Experimental Details
A series of arc melted Fe1xAlx alloy samples were pre-
pared under Argon atmosphere using high purity (more
than 99.9%) constituent’s metals. Afterwards, the poly-
crystalline ingots were annealed at 600˚C for 120 hr un-
der the UHV condition.
The structure, average grain size and lattice constant a0
of each sample was inferred from the X-ray diffraction
(XRD). In the present study, the average crystallite size
<L> was calculated from the broadening of XRD peaks
*Corresponding author.
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according to Scherrer’s formula
where k represented the shape factor which varied with
the crystal shape, λ is the wavelength of the CuKα radia-
tion, θ is the Bragg angle, and
is the Lorentzian part
of the integral breadth due to the crystallite size.
The lattice parameter calculated using the equation
4sin hkl
The corresponding magnetic and resistivity measure-
ments were done using vibrating sample magnetometer
and standard four-probe resistivity method. The chemical
and electronic information of the samples at different
depth has been obtained from XPS technique. X-ray pho-
toelectron spectroscopy (XPS) study was carried out at a
base pressure better than 5 × 109 Torr. Hereafter, for
simplicity we have named the sample Fe80Al20 (x = 0.2)
as Sample A, Fe70Al30 (x = 0.3) as Sample B, Fe60Al40 (x =
0.4) as Sample C, Fe50Al50 (x = 0.5) as Sample D and
Fe40Al60 (x = 0.6) as Sample E.
3. Results and Discussion
Figure 1 displays the XRD patterns of Fe1xAlx (0.2 x
0.6) samples as a function of x. Only a narrow range of
diffraction angles is presented (2θ =25˚ - 55˚), but it
contains the main lines of all components and is repre-
sentative of the evolution that occurs. All the samples
show crystalline structure and textured mainly along (110)
direction, irrespective of the Al content. Figure 1(a)
shows the diffraction pattern of sample A (Fe80Al20). The
peak at 31.04˚ can be attributed to a new phase which
possesses the same structure type as the bcc Fe (Al). The
peak at 2θ = 39.3˚ of Al (111) is absent shows complete
Figure 1. XRD patterns of Fe1xAlx samples as a function of
dissolution of Al with Fe, which further supports the
formation of Fe (Al) solid solution. Further, it is seen that
the fundamental peaks are consistently broadened and
shifted to lower angles with increase in x. The broaden-
ing of the peaks is due to the rapid reduction in average
crystallite size and an increase in lattice strain. It is found
that that average crystallite size decreases rapidly with x
particularly after x > 0.3 (see Table 1). The shifting of
the fundamental peaks to lower angles indicates an ex-
pansion of the lattice and presence of internal strain oc-
curs as a result of non-uniform alloy formation during
sample preparation. The variation in lattice parameter (a0)
as a function of Al content is shown in Table 1. This can
be understood if we take into account that the Al atoms
enter the Fe lattice producing a local dilatation due to
their larger size.
The diffraction pattern of Sample C shows some mark-
ed differences. In addition to reduction in peak intensity
and shift in peak position, a small peak at 39.04˚ corre-
sponds to Al (111) is also present in the pattern indicat-
ing that whole Al does not mix completely with Fe to
form uniform FeAl alloy. As already mentioned, Arc
melting process is a non-equilibrium process and has no
sufficient time to form stable and ordered phases, so
meta-stable and disordered phases will be formed. Fur-
ther considerable reduction in the peak intensity of Sam-
ples D and E with x clearly indicates the structural trans-
formation and formation of Al rich FeAl phases. The
average crystallite size in these cases are reduces drasti-
cally to 28 nm and 26 nm, respectively. After seeing the
results one may expect the formation of an off stoichio-
metric Fe3Al phase in the Fe-rich samples, while the
Al-rich compositions have both Al-rich phases and clus-
tering of Fe and Al atoms, respectively.
The corresponding hysteresis loops M (H) for all the
samples were obtained at room temperature using a VSM,
with a maximum applied field of 14 kOe (see Figure 2).
From the inset of Figure 2(a) it is clearly seen that Sam-
ple A show saturation with applied magnetic field indi-
cating the ferromagnetic nature of the sample with a
strong anisotropy leading to in plane easy direction of the
Table 1. Parameters obtained from XRD and VSM data
analysis for Fe1xAlx alloy samples as a function of x.
L (nm)a0)
(cm) Hc (Oe)Ms (emu)
x = 0.2 1162.879 93 1.7 3.22
x = 0.3 1112.883 117 2.9 1.88
x = 0.4 78 2.889 178 33.3 0.81
x = 0.5 28 2.894 165 71.7 0.045
x = 0.6 26 2.894 144 46.4 0.0046
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Figure 2. M-H curves of Fe1xAlx samples as a function of x, (a) Sample A; (b) Sample C; (c) Sample D; and (d) Sample E.
magnetization. However, magnetization and room tem-
perature ferromagnetic state gradually disappears with
increasing x, up to x 0.3. On further increasing x, the
ferromagnetic state disappears more rapidly, becoming
paramagnetic for alloys with x 0.4. The samples with
high Al content (x 0.4) do not show saturation even
after applying the maximum applied field of 14 kOe.
This characteristic reflects the gradual development of
alloying process of Fe with Al. Al reduces the direct fer-
romagnetic interaction between Fe-Fe sites and at the
same time increase in anti-ferromagnetic interaction
could takes place, which reduces the magnetic moment
of Fe. Further, there is also a shift in the hysteresis loop
indicating of moment pinning due to highly disordered
and non-uniform nature of the sample. This loop shift
can be explained as originating from the phenomena of
exchange bias [15] associated with the exchange anisot-
ropy created at the interface between AFM-FM phases. It
is also found that coercivity (Hc) increases with x (from
~1.7 Oe to ~71.7 Oe), see Table 1. The increase of Hc
with the decreasing particle size may indicate that pin-
ning at the grain boundaries may be important origin of
the coercivity; indeed smaller grain size corresponds to
larger number of grain boundaries results enhancement in
the anisotropy which act as barriers to the motion of the
domain walls, increasing thus the coercive field. Table 1
also shows the saturation magnetization value of the
Fe1xAlx samples as a function of x. The progressive de-
crease of the saturation magnetization is attributed to
competition between nearest neighbour Fe-Fe ferromag-
netic exchange and an indirect FeAl anti-ferromagnetic
interaction and the alloy become nonmagnetic around
0.5% Al. The system can be considered to be consisting
of a ferromagnetic phase dispersed in a non-magnetic
medium. The presence of spontaneous magnetization in
the system indicates that the magnetic grains are coupled
through exchange interactions. The exchange interaction
can be a Ruderman Kittele Kasuyae Yosida (RKKY)
type of interaction mediated by the itinerant electrons
present in the system or through a super-exchange type
of interaction due to the overlap of the electron wave
functions of the magnetic atoms with the Al electron
wave functions.
The value electrical resistivity of Fe1xAlx samples as a
function of x is shown in Table 1. It is seen that the re-
sistivity increases sharply with increase in x and show a
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maximum value of 178 cm at x = 0.4. The resistivity
initially increases with concentration as it should since
increasing disorder, brought about by rising Al concen-
tration, contributes to increasing electron scattering. In
addition, the formation of different phases of FeAl is
responsible for high value of resistivity. Further increase
of Al yields a steep decrease in the electrical resistivity,
and the resistivity of the FeAl alloy containing 60 at.%
Al approaches a value of 144 cm. It is easy to under-
stand from the electronic structure of Fe and Al atoms
that 3s orbitals of Al are very close in energy to the 3d
orbitals of Fe, thus providing the grounds for a strong
overlap between Fe-3d and Al-3s as these elements are
alloyed. But important to note that the 3p electrons of Al-
lie at an energy higher than the 3d and 4s electrons of Fe.
Thus, as these elements are alloyed, one would expect a
charge transfer from Al-3p to Fe-3d, as the 4s orbitals of
Fe are full and this charge transfer affect the resistivity as
well as magnetic moment of Fe due to filling of the 3d
orbitals. Further addition of Al above 40 at.% value es-
sentially adds more electrons to a nearly free electron
conduction band and the resistivity falls sharply.
Figure 3 shows the core level and valence band (VB)
spectra of Sample B and D recorded after 90 min of sput-
tering. The recorded spectrum of Fe and Al shows some
significant differences, which are characteristics of the
oxidized state (see Figures 3(a) and (b)). The Fe-2p
spectrum is split by the 2p-spin–orbit effect into the 2p3/2
and 2p1/2 regions and continuous tail is caused by elec-
tron-hole pair excitations and is a signature of the metal-
lic states. Similarly, the set of typical Al-2p spectra con-
Figure 3. Fe-2p, Al-2p core levels and VB spectra of Sample
B and Sample D recorded after 90 min sputtering.
sist of spin orbit doublet peaks corresponding to Al-2P3/2
and Al-2p1/2 level states.
However, spectrometer resolution (0.8 eV) does not
allow distinction of their structure. Another important
point is that the relative intensity of Al-Ox peak is higher
than pure Al-2p peak indicating that oxygen is mainly
reacted with Al and partially with Fe (see Figures 3(a)
and (b)). The corresponding VB spectra show three dis-
tinct features; a broad Fe-3d band around 2.3 eV near the
Fermi level and other broad band lying deeper in energy
at 6.3 eV are attributed to π and σ molecular orbitals,
respectively formed by the hybridization of Al-3sp and
O-2p orbitals and Al-3s band at 10.8 eV (see Figure
3(c)). However in case of sample D, Fe-2P3/2 peak is ob-
served at 707.1 eV and is shifted by 0.3 eV towards
higher binding energy and Al-2p peak by 0.35 eV but
towards lower binding energy as compared to their ele-
mental Fe-2p and Al-2p core line (see Figures 3(d) and
If we compare Samples B and D, we find some differ-
ences in the binding energy positions of Fe-2p and Al-2p
core lines. The binding energy of the Fe-2p peaks is
shifted towards higher binding energy and Al-2p towards
lower binding energy as compared to their element peak
position; also the shift in Sample B is different from
Sample D. The different shift in each case is due to the
formation of different phases of FeAl, i.e. Fe rich in
Sample B and Al rich in Sample D. Further in the VB
spectra of Sample D, one can see apart from 3d photo-
emission band of Fe at 1.8 eV, strong feature around 9.6
eV is also observed corresponding to Al-3s as is very
small in case of Sample B. Due to this, Fe-3d density of
states (DOS) are drastically modified and the emission
band is shifted towards lower binding energy i.e. towards
Fermi level. This is due to the strong hybridization of
sp-d states at Fermi level as a result of charge transfer
from valance Al-3p and 3s electrons to minority 3d or-
bital of Fe. Our results were matches well with the earlier
theoretical results.
4. Conclusion
The results conclude the formation of an off stoichio-
metric Fe3Al phase in Fe-rich samples, while the Al-rich
compositions have both Al-rich phases and clustering of
Fe and Al atoms The corresponding magnetic measure-
ments show decrease in saturation magnetization and
increase in resistivity with x and is attributed to dilution
of Fe moment in the Al rich compositions due to sp-d
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