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Submitted on 1 Jan 1988
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MAGNETIC PROPERTIES OF AMORPHOUS AND
CRYSTALLINE Fe-Hf-Si ALLOYS IN THE VICINITY
OF Fe3Si
T. Kamimori, E. Tanita, H. Takagi, H. Tange, M. Goto
To cite this version:
JOURNAL DE PHYSIQUE
Colloque C8, Supplkment au no 12, Tome 49, dkembre 1988
MAGNETIC PROPERTIES OF AMORPHOUS AND CRYSTALLINE Fe-Hf-Si ALLOYS IN THE VICINITY OF
Fe3Si
T. Kamimori, E. Tanita, H. Takagi, H. Tange and M. Goto Faculty of Science, Ehime University, Matsuyama 790, Japan
Abstract.
-
On both amorphous and crystallized Fe75HfrSi25-r alloys (5 5 x 5 7), p, TC and Hhf were studied. Distribution of Hhf suggested local precipitation occurs by crystallization. Measurements result in p(amo)>
p(cry) and Tc(amo) <Tc(cry). Thus, the predicted p and Tc for amo-
FesSi (x = 0) are 1.8-
1.9 p~ and 720 K, respectively.1. Introduction be detected by X-ray. On the other hand,
Bhf
of amoalloy decreases with increasing x. This fact suggests The ordered state of FesSi(D0, type) is so stable homogeneous dispersion of Hf atom in amo alloy. that it hardly breaks even by rapid quench. Howe-
ver, with the addition of Hf, amorphous state of quasi- FeoSi can be prepared by rapid quench [I]. In the pre- sent work, magnetic moment per Fe atom p and the Curie temperature
Tc,
together with distribution of hyperfine field Hhf, were studied in both amorphous (referred to as amo hereafter) and crystallized (cry) Fe7sHfaSi25-, alloys (55
x5
7) for comparison of the both states. ,u and Tc of amo-
Fe3Si were roughly es- timated by extrapolation of the measured values to x = 0. Specimens used were of ribbon with N 1 m m wide and-
10 pm thick.2. Results a n d discussion Hhf (kOe)
2.1 DISTRIBUTION OF Hhf .-Mossbauer spectrum of 5 7 ~ e was observed at 300 K. Distribution probability
P of Hhf for amo alloy, obtained by use of histogram [2], is composed of one large and three small Gaussians as shown in figure 1. The profile is almost unchanged with x. The peak field of 200 kOe of the main Gaussian corresponds to Hhf of (A, C) site and that of 310 kOe to Hhf of (B) site of FesSi [3]. Thus, contribution of Hf atom may be contained in two Gaussians at lower field side. On the other hand, in cry alloy there are six Hhf's. Five of them agree with the obtained vac
lue for nearest neighbour configuration [yFe, (8
-
y) Si] (y = 8, 7, 6, 5, 4) [4] which is the combination of Fe and Si only. Hhf with y less than 4 has never been found. The rest is nearly 0 kOe. Therefore, Hf atom must be responsible for Hhf=O kOe. These results for both amo and cry alloys show Hf atom plays a role largely weakening ferromagnetic coupling. Figures 2a and b show x dependence of distribution probability Pand averaged hyperfine field Hhr, respectively. In cry alloy, P for y = 8 largely increases and Hhf increases with increasing x. These facts suggest the development of an inhomogeneous structure containing local preci- pitation of iron by crystallization, though it could not
Fig. 1.
-
Distribution probability P of Hhf of amorphous alloy at 300 K.Fig. 2.
-
The x dependence of distribution probability P of HM in crystallized alloys; (a), and average hypefine field Rhf; (b).C8 - 152 JOURNAL DE PHYSIQUE
2.2 p.
-
Magnetization was measured in the range of 77 K-Tc. p was determined from the magnetization extrapolated t o 0 K. The obtained values are plotted against x by the circle in figure 3. ,u(amo) is always larger than p(cry). This result does not correspond t o that of H h f , because of much different measurement temperature. Result of p, the averaged moment at 0 K, might be illustrated in terms of the averaged Fe-Fe in- ter atomic distance; the distance is larger in amo than cry alloy: measurement of density p showed p(amo)<
p(cry) for the same x. Both p's increase with increasingx. The increase may attributable to mass difference between Hf and Si.
Figure 4 shows temperature dependence of magne- tization for x = 6. The plots for amo shift t o down- ward against cry alloy. The curves in the figure are the ones calculated on the basis of the fluctuation of
S, AS/S = 6 [5]. The curves for S = 1, 6 = 0 and
S = 1, 6 = 0.5 fit fairly well with the plots for cry and amo alloy, respectively. This behavior is almost the same for other x's and agrees with that of am^
Fea4Pd36P20 [6].
2.3 Tc.-The obtained Tc is given by the square in figure 3. Value of Tc (cry) is fairly large as compared with Tc (amo)
.
Tc (cry) increases with increasing x.On the contrary, Tc (amo) decreases. If there exists an inhomogeneous structure composed of regions ha- ving different Tc, the Tc being measured is not average of local Tc differently from the case of p, but it may
0
8
-
0
2
4
6
8
1
0
X
inFe75HfXSi25-X
Fig. 3.
-
The x dependence of p and Tc.0 : amo
: c r y
0
0
0.5
1.0
T
I
Tc
Fig. 4. - Temperature dependence of magnetization for
t = 6.
be largely affected by high local Tc. Therefore, value of Tc (cry) and its variation with x may be understan- dable by an inhomogeneous structure containing local precipitation of iron as described above.
2.4 AMORPHOUS Fe3Si.
-
Magnetic properties for amo-
FesSi can be estimated by extrapolating ones of amo-
Fe~~Hf,Si25-, t o x = 0. Extrapolation was done also on am~-Fe,s-,Hf,Si~~ system (75
x <_ 9) given by the cross attached t o circles or square in fi-gure 3. These simple extrapolations results in p =
1.8
-
1.9 p~ and Tc=720K
of amo-FesSi. Thus esti- mated p and Tc are respectively larger than p (cry) =1.6 pB and lower than Tc (cry) =850 K. The extrap* lated density of amo-FesSi is smaller than the measu- red one of cry-Fe3Si.
[l] Goto, M., Kamimori, T., Takagi, H., Tanita, E. and Tange, H., Proc. Int. Symp. on Non- equilibrium Solid Phases of Metals and Alloys (The Japan Institute of Metals) Suppl. to Trans. JIM 29 (1988) 371.
[2] Hesse, J. and Rubartsch, A., J. Phys. E 7 (1974) 1808.
[3] Heine, W. A., Menotti, A. H., Budnick, J. I., Burch, T. J., Litrenta, T., Niculescu, V. and Raj,
K., Phys. Rev. B 13 (1976) 4060.
[4] Sterns, M. B., Phys. Rev. 129 (1963) 1136.
[5] Handrick, K., Phys. Status Solidi 3 2 (1969) K55. [6] Sharon, T. E. and Tsuei, C. C., Phys. Rev. B 5
