- Email: [email protected]
Structural and magnetic properties of Cu80Fe5Ni15 granular ribbons
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763 www.elsevier.com/locate/jmmm
Structural and magnetic properties of Cu80Fe5Ni15 granular ribbons S. Cazottesa, A. Fnidikia,, D. Lemarchanda, F. Danoixa, P. Ochinb a
Groupe de Physique des Mate´riaux, UMR CNRS 6634, Site Universitaire du Madrillet, BP12, 76801 Saint Etienne du Rouvray cedex, France b CECM CNRS, 94497 Vitry Cedex, France Available online 13 March 2007
Abstract Microstructure and magnetic properties of as-quenched melt-spun Cu80Fe5Ni15 ribbon have been studied. The microstructure was investigated with X-ray diffraction and transmission electron microscopy (TEM). Magnetization measurements, Mo¨ssbauer spectrometry has been used in order to determine the magnetic properties. The microstructure of the ribbon is compatible with the presence of two spinodally decomposed FCC phases: a Cu-rich and a (Fe,Ni)-rich phase. The Mo¨ssbauer spectrum was well adjusted with two contributions: one from the Cu-rich phase and the other from the (Fe,Ni)-rich phase. From Mo¨ssbauer and ZFC/FC measurements, the ribbon shows a superparamagnetic behavior at 300 K, and a Super Spin Glass behavior below Tg ¼ 20 K. Fitting the magnetization curves provided a medium size of the magnetic particles diameter of 3.1 nm, with the maximum magnetic particle diameter calculated from ZFC/FC curve of 11 nm. Finally, magnetoresistance curves show no hysteresis, and the values measured were 15% at 5 K and 0.2% at 300 K for a maximum applied field of 50 kOe. r 2007 Elsevier B.V. All rights reserved. PACS: 73.43.Qt; 75.50.Tt; 61.46.+w Keywords: Cu–Fe–Ni system; Superparamagnetic particle; Magnetization
1. Introduction Granular solids consisting of magnetic fine particles embedded in a non-magnetic medium have been intensively studied in the last decade because of their interesting physical properties and of their potential technological applications. Indeed, these materials exhibit novel phenomena such as superparamagnetism, giant magnetoresistance (GMR) and giant magnetic coercivity. The Cu–Fe–Ni system is an interesting system since large GMR values has been observed for the Cu-rich composition [1–3]. As the GMR effects are strongly dependent on microstructural parameters like the size, the number density, the distribution of the magnetic particles, it is important to determine both the microstructure of the material and the magnetic properties of each phase. The aim of this work is to correlate the microstructure given by characterization Corresponding author. Tel.: +33 2 32 95 50 40; fax: +33 2 32 95 50 32.
E-mail address: [email protected] (A. Fnidiki). 0304-8853/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2007.03.086
techniques such as X-ray diffraction (XRD), and transmission electron microscopy (TEM) with the magnetic measurements such as magnetization, Zero Field Cooled and Field Cooled (ZFC/FC) curves and Mo¨ssbauer measurements. 2. Experimental procedures Cu80Fe5Ni15 (at%) ribbons were prepared by conventional melt spinning and rapid solidification process in an argon atmosphere using a steel wheel rotating at a surface speed of 25 m/s. The ribbons were 1 cm wide, 20–30 mm thick and about 1 m long. The structure of the ribbons was characterized by XRD, and TEM observations. Magnetic measurements were carried out by using a superconducting quantum interference device (SQUID) in a temperature range between 5 and 300 K with the applied field up to 50 kOe. The magnetoresistance of the ribbons was measured using the four points technique with a magnetic field up to 50 kOe applied in the ribbon plane.
ARTICLE IN PRESS S. Cazottes et al. / Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763
Mo¨ssbauer experiments were performed at room temperature using a 57Co source in a Rh matrix. The isomer shift at the 57Fe nucleus is given relative to a-Fe at room temperature. 3. Results 3.1. Structural characterization The structure of the melt-spun Cu80Fe5Ni15 ribbon was investigated using XRD. The XRD pattern for as-cast Cu80Fe5Ni15 is shown in Fig. 1. All the peaks can be indexed within the FCC structure, with an experimental lattice parameter of 0.3602 nm. The lattice parameters of FCC Cu and Ni are 0.3615 and 0.3524 nm, respectively. According to the Vegard’s law, the lattice parameter of the alloy deduced from these values is 0.3601 nm. This is in agreement with the experimental value. TEM observations of this sample showed that the ribbon is composed of Cu-rich FCC grains as shown in Fig. 2. Their size is in the range of 200–500 nm. According to the
Intensity (arb. units)
800 700 600 500 400 300 200 100
e761
previous studies [1–4], we expected to evidence a two phases microstructure, resulting from the spinodal decomposition of the high temperature g phase into two FCC phases: a Cu-rich phase and a (Fe,Ni)-rich one. However, a close inspection of the TEM micrograph could not reveal such a microstructure. Indeed, some complex contrasts are visible inside the grains but they could not be clearly associated with precipitation. Electron diffraction pattern shows the crystallographic structure of FCC Cu but no additional spots due to a second phase with different crystallographic parameters are visible on this pattern (see Fig. 2). Such observations are fully compatible with the presence of two demixed phases resulting from a spinodal decomposition, which would have similar lattices. 3.2. Mo¨ssbauer characterization In order to determine the magnetic state of the ribbon, the sample was characterized by 57Fe Mo¨ssbauer spectrometry, at 300 K, as shown in Fig. 3. The corresponding Mo¨ssbauer spectrum is an asymmetric doublet. It indicates that there is no large magnetic particle in the ribbon in agreement with structural characterization. The spectrum can be decomposed in two subspectra: a doublet associated with the Cu-rich phase and a singlet associated with the (Fe,Ni)-rich phase. The doublet has an isomer shift of 0.36 mm/s and a quadrupole splitting of 0.163 mm/s. The singlet has an isomer shift of 0.04 mm/s, which are close to the values obtained in an other investigation for CuFeNi [5]. 3.3. Magnetic properties
0 40
50
60
70
80
90
100
110
120
130
2 Theta(degrees) Fig. 1. X-ray diffractogram obtained with Co Ka. Radiation for the Cu80Fe5Ni15 sample. Peaks are indexed within the FCC structure.
The ZFC/FC measurements were made using an applied field of 10 Oe, see Fig. 4. There is a substantial increase in the ZFC curve below 20 K, followed by a decrease until room temperature. The FC and ZFC curves begin to diverge in the neighborhood of 100 K, and below this temperature, there is a discrepancy in magnetization Velocity (mm/s) -11
0
+11
Absorbtion (%)
1.00
0.97 Fig. 2. TEM Bright Field image showing the Cu-rich grains in a Cu80Fe5Ni15 as spun ribbon, and the diffraction pattern of the black FCC grain (112 zone axis).
Fig. 3. Mo¨ssbauer spectrum for as spun Cu80Fe5Ni15. Measurements at 300K.
ARTICLE IN PRESS S. Cazottes et al. / Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763
e762
0.005
FC
Moment (emu/g)
Moment (emu/g)
0.006
0.004 0.003 ZFC
0.002 0.001 0
0
50
100
150
200
250
300
10 8 6 4 2 0 -2 -4 -6 -8 -10 -55000
300K 5K
-35000
-15000
T irr ¼ KV max =25 kB , where Vmax is the volume of the largest particle, kB the Boltzmann constant and K a constant characteristic of the magnetic anisotropy of the sample. With the anisotropy of a-Fe (K ¼ 4.8 104 J/m3), Tirr ¼ 100 K and Tg ¼ 20 K, we found a maximal particle diameter Dmax11 nm. Using the Hansen model [7], the particle size range can be calculated and leads to a particle size range of about s1.2. The hysteresis loops were made at 5 and 300 K, as shown in Fig. 5. From the 300 K curve, a substantial increase of magnetization occurs between 10 and 50 kOe, the ribbon shows no hysteresis and it was not saturated at 50 kOe. It suggests the presence of a very fine-scale superparamagnetic phase. A small ferromagnetism appears at 5 K while it is not present at 300 K. The ribbon shows a very small hysteresis, and a maximum moment at 50 kOe of 9.6 emu/g at 5 K. At 300 K, the magnetization at 50 kOe is 2.0 emu/g at 300 K. The medium size of the unblocked magnetic particles can be calculated from the magnetization curves at 300 K. Since the magnetization had not saturated at 50 kOe, data were fitted [8] using the expression M ¼ MS(1a/H), in order to obtain the saturation magnetization MS. We get MS ¼ 2.71 emu/g for the 300 K measurement. From the high field 300 K magnetization curve, we estimated the mean size of the unblocked magnetic nano-particles, assuming a lognormal distribution of particle volume [9]. The median
45000
Fig. 5. Experimental curve of magnetization vs. magnetic field for as spun Cu80Fe5Ni15, measured at 5 and 300 K.
Field (Oe) -60000 2
-40000
-20000
0
20000
40000
60000
0 -2 GMR (%)
between the two curves. The peak in the FC curve occurs close to 20 K followed by a sharp decrease until 5 K. According to Ref. [6], below the glass transition temperature Tg ¼ 20 K, this behavior is characteristic of a Super Spin Glass magnetism (SSG) and it appears for particles with substantial magnetic interactions at low temperature [6]. Some alternative susceptibility measurements should be made to confirm this behavior. Above Tg, the ribbon has a superparamagnetic behavior. From the ZFC/FC curves, the largest size of the unblocked particles can be related to the irreversibility temperature Tirr using the Bean–Livingston relation [4]:
25000
Field (Oe)
Temperature (K) Fig. 4. ZFC/FC magnetization curve of as spun Cu80Fe5Ni15.
5000
-4
5K 300K
-6 -8 -10 -12 -14 -16
Fig. 6. Magnetoresistance curve for as spun Cu80Fe5Ni15 measured at 5 K.
volume is V0 and kT s2 M ¼ Ms 1 exp , HV 0 M s 2 Z 1 mH L f ðmÞ dm, MðH; TÞ ¼ kT 0 where s is the width of the distribution function (determined from the ZFC/FC curve s1.2), L(x) the Langevin function, f(m) the magnetic moment distribution function and other quantities have their usual meanings. With the hypothesis that the particles are spherical, we obtain a medium diameter D03.1 nm for our sample. This value is in accordance previous studies [9]. The magnetoresistance was measured at 5 and 300 K, as shown in Fig. 6, up to the maximal field 50 kOe. The magnetoresistance ratio given by MR ¼ ½rðHÞ rðH ¼ 0Þ=rðH ¼ 0Þ. The maximum value was MR15% at 5 K and MR0.2% at 300 K. These values are similar to GMR values obtained previously [8], taking into account the fact that the maximum MR is not reached at 50 kOe.
ARTICLE IN PRESS S. Cazottes et al. / Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763
e763
The magnetoresistance curves, like the magnetization cycles present no hysteresis.
ture Mo¨ssbauer and Atom Probe to definitely evidence the presence of those particles.
4. Conclusion
References
From Mo¨ssbauer and ZFC/FC measurements, the ribbon shows a superparamagnetic behavior at 300 K, and a Super Spin Glass behavior below Tg ¼ 20 K. Magnetic measurements give information about the magnetic particle size and their size distribution in the sample. The size distribution is rather big (s1.2), with a medium diameter of 3.1 nm and a maximum particle size of 11 nm. According to previous studies [2–4], those particles could be formed by spinodal decomposition and have the same FCC structure as the copper matrix. More experiment are in progress by high-resolution TEM, Energy Filtered Transmission Electron Microscopy, low tempera-
[1] L.H. Chen, S. Jin, T.H. Tiefel, S.H. Chang, M. Eibschtuz, Phys. Rev. B 49 (13) (1994) 9194. [2] M. Barrico, E. Bosco, G. Acconciaioco, P. Rizzi, M. Coisson, Mater. Sci. Eng. A375 (377) (2004) 1019. [3] L.H. Chen, S. Jin, T.H. Tiefel, S.H. Chang, M. Eibschtuz, J. Appl. Phys. 79 (1996) 5599. [4] C. Servant, B. Sundman, O. Lyon, Calphad 25 (1) (2001) 79. [5] I. Navarro, M.El. Ghannami, C. Gomez Polo, M. Vasquez, A. Hernando, J. Magn. Magn. Mater. 140 (144) (1995) 361. [6] O. Petracic, X. Chen, S. Bedanta, W. Kleemann, S. Sahoo, S. Cardoso, P.P. Freitas, J. Magn. Magn. Mater. 300 (2006) 192. [7] M.S. Hansen, F.P. Mørup, J. Magn. Magn. Mater. 203 (1999) 214. [8] C.S. Martins, F.P. Missel, J. Appl. Phys. 83 (11) (1998) 7001. [9] C.S. Martins, F.P. Missel, J. Appl. Phys. 89 (11) (2001) 7298.
Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763 www.elsevier.com/locate/jmmm
Structural and magnetic properties of Cu80Fe5Ni15 granular ribbons S. Cazottesa, A. Fnidikia,, D. Lemarchanda, F. Danoixa, P. Ochinb a
Groupe de Physique des Mate´riaux, UMR CNRS 6634, Site Universitaire du Madrillet, BP12, 76801 Saint Etienne du Rouvray cedex, France b CECM CNRS, 94497 Vitry Cedex, France Available online 13 March 2007
Abstract Microstructure and magnetic properties of as-quenched melt-spun Cu80Fe5Ni15 ribbon have been studied. The microstructure was investigated with X-ray diffraction and transmission electron microscopy (TEM). Magnetization measurements, Mo¨ssbauer spectrometry has been used in order to determine the magnetic properties. The microstructure of the ribbon is compatible with the presence of two spinodally decomposed FCC phases: a Cu-rich and a (Fe,Ni)-rich phase. The Mo¨ssbauer spectrum was well adjusted with two contributions: one from the Cu-rich phase and the other from the (Fe,Ni)-rich phase. From Mo¨ssbauer and ZFC/FC measurements, the ribbon shows a superparamagnetic behavior at 300 K, and a Super Spin Glass behavior below Tg ¼ 20 K. Fitting the magnetization curves provided a medium size of the magnetic particles diameter of 3.1 nm, with the maximum magnetic particle diameter calculated from ZFC/FC curve of 11 nm. Finally, magnetoresistance curves show no hysteresis, and the values measured were 15% at 5 K and 0.2% at 300 K for a maximum applied field of 50 kOe. r 2007 Elsevier B.V. All rights reserved. PACS: 73.43.Qt; 75.50.Tt; 61.46.+w Keywords: Cu–Fe–Ni system; Superparamagnetic particle; Magnetization
1. Introduction Granular solids consisting of magnetic fine particles embedded in a non-magnetic medium have been intensively studied in the last decade because of their interesting physical properties and of their potential technological applications. Indeed, these materials exhibit novel phenomena such as superparamagnetism, giant magnetoresistance (GMR) and giant magnetic coercivity. The Cu–Fe–Ni system is an interesting system since large GMR values has been observed for the Cu-rich composition [1–3]. As the GMR effects are strongly dependent on microstructural parameters like the size, the number density, the distribution of the magnetic particles, it is important to determine both the microstructure of the material and the magnetic properties of each phase. The aim of this work is to correlate the microstructure given by characterization Corresponding author. Tel.: +33 2 32 95 50 40; fax: +33 2 32 95 50 32.
E-mail address: [email protected] (A. Fnidiki). 0304-8853/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2007.03.086
techniques such as X-ray diffraction (XRD), and transmission electron microscopy (TEM) with the magnetic measurements such as magnetization, Zero Field Cooled and Field Cooled (ZFC/FC) curves and Mo¨ssbauer measurements. 2. Experimental procedures Cu80Fe5Ni15 (at%) ribbons were prepared by conventional melt spinning and rapid solidification process in an argon atmosphere using a steel wheel rotating at a surface speed of 25 m/s. The ribbons were 1 cm wide, 20–30 mm thick and about 1 m long. The structure of the ribbons was characterized by XRD, and TEM observations. Magnetic measurements were carried out by using a superconducting quantum interference device (SQUID) in a temperature range between 5 and 300 K with the applied field up to 50 kOe. The magnetoresistance of the ribbons was measured using the four points technique with a magnetic field up to 50 kOe applied in the ribbon plane.
ARTICLE IN PRESS S. Cazottes et al. / Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763
Mo¨ssbauer experiments were performed at room temperature using a 57Co source in a Rh matrix. The isomer shift at the 57Fe nucleus is given relative to a-Fe at room temperature. 3. Results 3.1. Structural characterization The structure of the melt-spun Cu80Fe5Ni15 ribbon was investigated using XRD. The XRD pattern for as-cast Cu80Fe5Ni15 is shown in Fig. 1. All the peaks can be indexed within the FCC structure, with an experimental lattice parameter of 0.3602 nm. The lattice parameters of FCC Cu and Ni are 0.3615 and 0.3524 nm, respectively. According to the Vegard’s law, the lattice parameter of the alloy deduced from these values is 0.3601 nm. This is in agreement with the experimental value. TEM observations of this sample showed that the ribbon is composed of Cu-rich FCC grains as shown in Fig. 2. Their size is in the range of 200–500 nm. According to the
Intensity (arb. units)
800 700 600 500 400 300 200 100
e761
previous studies [1–4], we expected to evidence a two phases microstructure, resulting from the spinodal decomposition of the high temperature g phase into two FCC phases: a Cu-rich phase and a (Fe,Ni)-rich one. However, a close inspection of the TEM micrograph could not reveal such a microstructure. Indeed, some complex contrasts are visible inside the grains but they could not be clearly associated with precipitation. Electron diffraction pattern shows the crystallographic structure of FCC Cu but no additional spots due to a second phase with different crystallographic parameters are visible on this pattern (see Fig. 2). Such observations are fully compatible with the presence of two demixed phases resulting from a spinodal decomposition, which would have similar lattices. 3.2. Mo¨ssbauer characterization In order to determine the magnetic state of the ribbon, the sample was characterized by 57Fe Mo¨ssbauer spectrometry, at 300 K, as shown in Fig. 3. The corresponding Mo¨ssbauer spectrum is an asymmetric doublet. It indicates that there is no large magnetic particle in the ribbon in agreement with structural characterization. The spectrum can be decomposed in two subspectra: a doublet associated with the Cu-rich phase and a singlet associated with the (Fe,Ni)-rich phase. The doublet has an isomer shift of 0.36 mm/s and a quadrupole splitting of 0.163 mm/s. The singlet has an isomer shift of 0.04 mm/s, which are close to the values obtained in an other investigation for CuFeNi [5]. 3.3. Magnetic properties
0 40
50
60
70
80
90
100
110
120
130
2 Theta(degrees) Fig. 1. X-ray diffractogram obtained with Co Ka. Radiation for the Cu80Fe5Ni15 sample. Peaks are indexed within the FCC structure.
The ZFC/FC measurements were made using an applied field of 10 Oe, see Fig. 4. There is a substantial increase in the ZFC curve below 20 K, followed by a decrease until room temperature. The FC and ZFC curves begin to diverge in the neighborhood of 100 K, and below this temperature, there is a discrepancy in magnetization Velocity (mm/s) -11
0
+11
Absorbtion (%)
1.00
0.97 Fig. 2. TEM Bright Field image showing the Cu-rich grains in a Cu80Fe5Ni15 as spun ribbon, and the diffraction pattern of the black FCC grain (112 zone axis).
Fig. 3. Mo¨ssbauer spectrum for as spun Cu80Fe5Ni15. Measurements at 300K.
ARTICLE IN PRESS S. Cazottes et al. / Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763
e762
0.005
FC
Moment (emu/g)
Moment (emu/g)
0.006
0.004 0.003 ZFC
0.002 0.001 0
0
50
100
150
200
250
300
10 8 6 4 2 0 -2 -4 -6 -8 -10 -55000
300K 5K
-35000
-15000
T irr ¼ KV max =25 kB , where Vmax is the volume of the largest particle, kB the Boltzmann constant and K a constant characteristic of the magnetic anisotropy of the sample. With the anisotropy of a-Fe (K ¼ 4.8 104 J/m3), Tirr ¼ 100 K and Tg ¼ 20 K, we found a maximal particle diameter Dmax11 nm. Using the Hansen model [7], the particle size range can be calculated and leads to a particle size range of about s1.2. The hysteresis loops were made at 5 and 300 K, as shown in Fig. 5. From the 300 K curve, a substantial increase of magnetization occurs between 10 and 50 kOe, the ribbon shows no hysteresis and it was not saturated at 50 kOe. It suggests the presence of a very fine-scale superparamagnetic phase. A small ferromagnetism appears at 5 K while it is not present at 300 K. The ribbon shows a very small hysteresis, and a maximum moment at 50 kOe of 9.6 emu/g at 5 K. At 300 K, the magnetization at 50 kOe is 2.0 emu/g at 300 K. The medium size of the unblocked magnetic particles can be calculated from the magnetization curves at 300 K. Since the magnetization had not saturated at 50 kOe, data were fitted [8] using the expression M ¼ MS(1a/H), in order to obtain the saturation magnetization MS. We get MS ¼ 2.71 emu/g for the 300 K measurement. From the high field 300 K magnetization curve, we estimated the mean size of the unblocked magnetic nano-particles, assuming a lognormal distribution of particle volume [9]. The median
45000
Fig. 5. Experimental curve of magnetization vs. magnetic field for as spun Cu80Fe5Ni15, measured at 5 and 300 K.
Field (Oe) -60000 2
-40000
-20000
0
20000
40000
60000
0 -2 GMR (%)
between the two curves. The peak in the FC curve occurs close to 20 K followed by a sharp decrease until 5 K. According to Ref. [6], below the glass transition temperature Tg ¼ 20 K, this behavior is characteristic of a Super Spin Glass magnetism (SSG) and it appears for particles with substantial magnetic interactions at low temperature [6]. Some alternative susceptibility measurements should be made to confirm this behavior. Above Tg, the ribbon has a superparamagnetic behavior. From the ZFC/FC curves, the largest size of the unblocked particles can be related to the irreversibility temperature Tirr using the Bean–Livingston relation [4]:
25000
Field (Oe)
Temperature (K) Fig. 4. ZFC/FC magnetization curve of as spun Cu80Fe5Ni15.
5000
-4
5K 300K
-6 -8 -10 -12 -14 -16
Fig. 6. Magnetoresistance curve for as spun Cu80Fe5Ni15 measured at 5 K.
volume is V0 and kT s2 M ¼ Ms 1 exp , HV 0 M s 2 Z 1 mH L f ðmÞ dm, MðH; TÞ ¼ kT 0 where s is the width of the distribution function (determined from the ZFC/FC curve s1.2), L(x) the Langevin function, f(m) the magnetic moment distribution function and other quantities have their usual meanings. With the hypothesis that the particles are spherical, we obtain a medium diameter D03.1 nm for our sample. This value is in accordance previous studies [9]. The magnetoresistance was measured at 5 and 300 K, as shown in Fig. 6, up to the maximal field 50 kOe. The magnetoresistance ratio given by MR ¼ ½rðHÞ rðH ¼ 0Þ=rðH ¼ 0Þ. The maximum value was MR15% at 5 K and MR0.2% at 300 K. These values are similar to GMR values obtained previously [8], taking into account the fact that the maximum MR is not reached at 50 kOe.
ARTICLE IN PRESS S. Cazottes et al. / Journal of Magnetism and Magnetic Materials 316 (2007) e760–e763
e763
The magnetoresistance curves, like the magnetization cycles present no hysteresis.
ture Mo¨ssbauer and Atom Probe to definitely evidence the presence of those particles.
4. Conclusion
References
From Mo¨ssbauer and ZFC/FC measurements, the ribbon shows a superparamagnetic behavior at 300 K, and a Super Spin Glass behavior below Tg ¼ 20 K. Magnetic measurements give information about the magnetic particle size and their size distribution in the sample. The size distribution is rather big (s1.2), with a medium diameter of 3.1 nm and a maximum particle size of 11 nm. According to previous studies [2–4], those particles could be formed by spinodal decomposition and have the same FCC structure as the copper matrix. More experiment are in progress by high-resolution TEM, Energy Filtered Transmission Electron Microscopy, low tempera-
[1] L.H. Chen, S. Jin, T.H. Tiefel, S.H. Chang, M. Eibschtuz, Phys. Rev. B 49 (13) (1994) 9194. [2] M. Barrico, E. Bosco, G. Acconciaioco, P. Rizzi, M. Coisson, Mater. Sci. Eng. A375 (377) (2004) 1019. [3] L.H. Chen, S. Jin, T.H. Tiefel, S.H. Chang, M. Eibschtuz, J. Appl. Phys. 79 (1996) 5599. [4] C. Servant, B. Sundman, O. Lyon, Calphad 25 (1) (2001) 79. [5] I. Navarro, M.El. Ghannami, C. Gomez Polo, M. Vasquez, A. Hernando, J. Magn. Magn. Mater. 140 (144) (1995) 361. [6] O. Petracic, X. Chen, S. Bedanta, W. Kleemann, S. Sahoo, S. Cardoso, P.P. Freitas, J. Magn. Magn. Mater. 300 (2006) 192. [7] M.S. Hansen, F.P. Mørup, J. Magn. Magn. Mater. 203 (1999) 214. [8] C.S. Martins, F.P. Missel, J. Appl. Phys. 83 (11) (1998) 7001. [9] C.S. Martins, F.P. Missel, J. Appl. Phys. 89 (11) (2001) 7298.