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57Fe AND 119Sn MÖSSBAUER INVESTIGATIONS OF Fe3-xSnxO4 WITH x UP TO 0.3
K. Melzer, G. Dehe, H. Mehner
To cite this version:
K. Melzer, G. Dehe, H. Mehner. 57Fe AND 119Sn MÖSSBAUER INVESTIGATIONS OF Fe3- xSnxO4 WITH x UP TO 0.3. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-181-C1-182.
�10.1051/jphyscol:1980152�. �jpa-00219721�
JOURNAL DE PHYSIQUE Colloque Cl, strpplkment au n O 1 , Tome 41, janvier 1980, page C1-181
5 7 ~ e /UD 'l9sn MbSBAUER INVESTIGATIONS OF Fe3-&04 WITH X UP TO 0 - 3 K. Melzer, G. Dehe and A. Mehner
+
Sektion Physik der KarZ-Marx-Universitdt Leipzig, DDR.
+
ZentraZinstitut fUr PhysikaZische Chemie der Akademie der Wissenschaften der DDR, Berlin.The most important process for the exis- tence of the magnetic hyperfine field at the I9sn nuclei in the f errimagnetic system Fe3-xSn 0 is the supertransfer of
x 4
3d-electron density from the A site Fe ion to the 5s orbital of sn4+ via an in- tervening oxygen ion /? /. Iheref ore, the '
' '
~
n Mossbauer spectrum of this system is essentially influenced by the distri- bution of the Fe2+ and Fe3+ on A sites.
An attempt was made to determine the cat- ion distribution for larger x values by using an analysis of 5 7 ~ e MiZssbauer spec- tra recorded at 80 K. The
'
I9sn spectra are interpreted on the basis of this cat- ion distribution.The samples were prepared by heating a mixture of Fe 0 FeO, and Sn02 powders
3
4'
for five hours at I050 C in a sealed-off evacuated quartz tube. In magnetite tin ions occupy only B sites /2/ in a tetra- valent state according to the equivalence 2 (Fe3' 1- ( ~ n 4 + )
+
( Fe2+ 1. up to xcO.1 the cation distribution for such a system is approximately5 7 ~ e and 'I9sn MiSssbauer spectra were ob- tained by use of 10 mCi 5 7 ~ o / ~ t and
4
mCiI9sn/ cal 1 9 ~ n ~ 3 sources.
The 1 9 ~ n spectrum shows a well-resolved six-line pattern mainly caused by the Fe3+
ions at the first neighbouring A sites
around the sn4+ ( e.g. for x = 0.01, the Line width is about 1.5 m/s, that is 1.3 times the experimental line width of the used spectrometer ).
. .
. . r % .,.-
'., \.. .
.
A,, 'r:
.
Y ,, .Fig. 1 : 'I9sn KiSssbauer epeotrs of Fe3-,Snx04 at 295 K.
With increasing x value the experimental spectra ( some spectra are shown in fi-
g w e 1 ) can only be fitted by a simple sextet asswing a considerable line broadening. Frox the marked changes in
Table I
the 'I9sn spectra for x 20.2 it is
HZ&
(kOe 1215 206 200 161 126
X
0.01 0 05 0.1 0.2 0.3
line width (mm/s) (lines 1 and 6)
1 5 2.2 30 1 6.2 6.8
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980152
C1-182 JOURNAL DE PHYSIQUE
assumed that more and more Fe2+ occupy x bauer level takes place any longer.
sites. The expected cation distribution is
where y is unknown. One has, for x = 0.2,
Fig. 2 : 5 7 ~ e M6ssbauer spectra of Fe2. 8Sn0;204.
The 57pe RT spectrum for x = 0.2 can be decomposed into two six-line patterns:
the A spectrum and the strongly asymmet- rically broadened B spectrum. No doublet of possible paramagnetic Fe2+ at X sites /3/ was observed up to x S 0.3. In order to get a better separation into an h and B subspectrum, the 5 7 ~ e spectrum for x = 0.2 at HT was measured in an external magnetic field of 12 kOe. It was found
that I(B)/I(B) = 2.46, from which we con- cluded if no separate Fe3+(B) exist y = 0.19 and if separate F ~ ~ + ( B ) exist y=0.41.
In figure 2 the 5 7 ~ e spectrum for x = 0.2 recorded at 80 K is shown. At this tem- perature this spectrum consists of the subspectra of the Fe2+*and Fe3+ at A and B sites since no fast electron exchslnge as compared to the life-time of the M6ss-
Table I1
Ratio of the subspectra intensities,x=0.2.
From the result of the least-squares fit of 3 sets OF six-line patterns to the 5 7 ~ e spectrum at 80 K it follows y
=
0.4.The probability of finding n Fe2+ at A sites in the nearest neighbourhood of a B
6 n
site ~ n 4 + is given by P(n,y)=(,)y (1-y16-n The 1 1 9 ~ n spectra at RT was fitted by con- straining the line widths of the subspec- tra to be equal (1.5 rnm/s).
Table 111: Results of the fits.
Y Fe2+(g) pe2+(B) Fe3%/~) 0.08 /2/
0.19 0.37 /3/
0.41
The relative intensities obtained agree quite well with the calculated probabili- ties Dor y=0.33 (xn0.2) and ys0.52 (xt0.31 The y values which were determined from magnetization measurements /2/ are by far too small for x r 0.2. It was found that ys0.35 for x=0.2 and y w 0.5 for x=0.3.
References
/I/ Watson, R.Z. and Freeman, A.J., Phys.
Rev.
123
(1961 ) 2027./2/ Basile, F., Djega-Niariadassou, C.,and Poix, P., J. Phys. Chem. Solids
2fi
(1974) 1067.
/3/ Evans, B. J., Lu San Pan, and Vogel,R., AIP Conf. Proc.
a
(1975) 390.x 0.2
0.3
1 1 I 1 fitted spectrum 1.
Subspectrum Nn=l NnZ3 Nnt4 Nn,5 14
5.3 2.2 1.9
20 8.4 4.3 3.9
2 2.1
24.5 104 25.0
98 Intensity
Heff(kOe) Intensity Heff(kOe)
29.5 168 20.5 161
- -
19.9 73 26.3
197 8.4 198
19.7 136 26.2 131
