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Submitted on 1 Jan 1971
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NEUTRON DIFFRACTION STUDY OF ErFe2
M. Bargouth, G. Will
To cite this version:
M. Bargouth, G. Will. NEUTRON DIFFRACTION STUDY OF ErFe2. Journal de Physique Collo- ques, 1971, 32 (C1), pp.C1-675-C1-676. �10.1051/jphyscol:19711235�. �jpa-00214063�
JOURNAL DE PHYSIQUE Colloque C I , supplkment au no 2-3, Tome 32, Fkvrier-Mars 1971, page C 1 - 675
NEUTRON DIFFRACTION STUDY OF ErFez
M. 0. BARGOUTH and G. WILL
Mineralogisches Institut der Universitiit Bonn, Abteilung fur Kristallstrukturlehre und Neutronenbeugung, Bonn, Germany
RBsum6. - Le composk ferromagnktique ErFez a kt6 ktudik par diffraction de neutrons et la variation avec la temp&
rature de l'aimantation des sous-reseaux a ete mesuree. L'ordre magnetique des ions d'erbium et de fer s'etablit B 600 OK.
Le comportement different des deux types d'ions quand la tempkrature varie, conduit a un maximum secondaire de l'aiman- tation 525 OK et B un point de compensation a 410 OK. Les moments A saturation de l'erbium et du fer sont respective- ment 8,5 et 2,O PB.
Abstract. - Ferrimagnetic ErFez has been studied by neutron diffraction, and the temperature dependence of the sublattice magnetization has been determined. Magnetic ordering of the erbium and iron ions starts at 600 OK. The diffe- rent temperature behavior of the two ion species leads to a secondary maximum in the magnetization at 525 OK and a compensation point at 410 OK. The saturation moments for erbium and iron are resp. 8.5 and 2.0 PB.
Introduction. - Compounds having the general formula RX,, where R is a rare earth element and X is aluminum, or a 3 d or 4 d element have been studied in great numbers for their magnetic, thermal and structural characteristics [I]. The sublattice magnetization is of special interest, when X is a 3 d- element. In the case of nickel there is an electron transfer from the rare earth to fill the nickel 3 d-band, while in the case of Mn, Fe or Co the transition element carries a moment.
We have undertaken a neutron diffraction study of ErFe,, in order to determine the magnetic proper- ties of the erbium and iron ions. Also, for ErFe, magnetic measurements have been reported by Wallace and Scarbek [2] and by Buschow and van der Goot [3].
Antiparallel coupling of the erbium to the iron has been deduced and as a consequence a compensation point was observed by these authors at 480 OK a n d also a secondary maximum of the magnetization at 530 OK.
On the other hand, however, Crangle and Ross [4]
do not report the occurrence of such a maximum in their magnetization vs. temperature curve.
Experimental. - ErFe, crystallizes with the cubic MgCu,-type of structure with a = 7.283 $- 0.003 A
a t room temperature and a = 7.246 f 0.003 A at 4.2 OK. Neutron diffraction data were collected in the temperature range from 4.2 OK to 700 OK in a cryostat and a quartz furnace at the research reactor DIDO, Julich, from a polycrystalline cylinderical sample 7 mm in diameter and 30 mm heigh, containing about 5 g of material. The neutron wave length was 0.971 A.
The measured absorption in the center of the sample was 22 %
MAGNETIC STRUCTURE. - The full neutron diffrac- tion diagrams were collected at six temperatures and the temperature dependence of the magnetic reflections was measured individually. The peaks, arising from magnetic ordering, agree with the anticipated ferri-
magnetic structure with the erbium moments being antiparallel coupled to the iron moments. A picture of the magnetic structure is given in figure 1. Since the diffraction from the different (hk1)-planes is depen- dent partly on the sum and on the difference of the
FIG. 1. - Ferrimagnetic structure of ErFez, which crystallizes in the cubic Lave phase MgCu2-type structure.
scattering of erbium and iron, and partly only on one member, we can deduce directly the separate magnetic behavior of the erbium and iron ions from the temperature dependence of the different reflections.
This is shown in figure 2. From the (222) and (220), (422) we can deduce separately the transition tempera- tures for Fe and Er, which are both at 600° * lo0 K.
This compares well with TN = 596 OK reported by Wallace [2] and 5900K reported by Buschow [3].
Figure 3 depicts the sublattice magnetization for the erbium and iron ions as a function of temperature. The compensation point at 4100K and the secondary maximum in the magnetization at 525 OK, as reported previously by Wallace and Scarbek [2] and by Bus-
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19711235
C 1 - 676 M. 0. BARGOUTH AND G . WILL
Temperature , OK
FIG. 3. - The sublattice magnetization of the erbium and iron ions, as calculated by least squares adaption from the diffracted neutron intensities at different temperatures. The Er and Fe moments are oriented antiparallel to each other. The total magnetization, indicated by the dashed line ErFea, shows therefore a compensation point at 410% and a secondary
maximum at 525 OK.
Temperature , %
FIG. 2. - Temperature dependence of the magnetic intensity as diffracted from different planes. The intensity of the (222)
reflection is solely the diffraction by the iron moments. The N6el
temperature is 600 OK.
chow and van der Goot [3] can be clearly seen in this diagram. I t can be explained by the magnetization at the iron sites, which manifests itself also in the tempe- rature dependence of the (222)-reflection of figure 2.
The magnetization of the iron ion increases rapidly until about 500 OK and then stays nearly unchanged down to 4.2 OK.
Complete diffraction diagramms were run at 6350, 5900, 5400,5000,3000,77° and 4.2 OK, in order to calculate the magnetic moments for iron and erbium from the observed magnetic scattering. The form factor values for erbium were taken from Will [5], which are the experimental average from several neu- tron diffraction studies on comvounds containing
Discussion. - The saturation moments for iron and erbium are resp. 2.0 + 0.05 pB and 8.5 f: 0.10 pB giving a total moment per ErFe, formula unit of 4.55 pB. The values for the ions are slightly higher than those reported by Wallace [2] (1.7 and 8.1 pB) at 4.2 OK. The moment of the erbium ions is however still lower than the expected theoretical value for erbium in an ordered state (9.0 pB). The iron on the other hand carries nearly the full moment of the metallic iron (2.22 pB), and there is no charge transfer from erbium to iron.
pEr pre p E r ~ e 2
erbium, and for iron from ree em an and Watson [6], Acknowledgement. - We acknowledge gratefully
< q2 > = 213 due to the cubic symmetry. The values the help of W. Meyer, Siemens Forschungs Labora- for p were calculated by least squares methods and torium, Miinchen, for providing the sample of
are listed in table I. ErFe,.
References
[ I ] WALLACE (W. E.), Progress in the Science and Techno- [2] WALLACE (W. E.) and SCRABEK (F. A.), Rare Earth logy of the Rare Earths, Vol. 3 by LeRoy Eyring, Research 11, Gordon and Breach,New-York, 1964.
Pergamon Press, Oxford, 1968. [3] BUSCHOW (K. H. J.) and VAN DER GOOT (A. S.), Phys.
Stat. Sol., 1969, 35, 515.
J.)s WERNICK (J. H.)9 NESBITT @. A') [4] CRANGLE (J.) and Ross (J. W.), Proc. Conf. on Magne- and SHERWOOD (R. C.), J. Phys. Soc. Japan, 1962,
17, Suppl. B-I, 91. tism, Nottingham, 1964.
[5] WILL (G.), 2. fiiY angew. Physik, 1969, 26, 67.
MANSMANN (M.) and WALLACE (W. E.), J . Chem. [6] WATSON (R. E.) and FREEMAN (A. J.), Acta Cryst.,
Phys., 1964, 40, 1167. 1961, 14, 27.
Cryostat 4.2 OK
8.47 1.97 4.53
Furnace 293OK
---
4.75 1.74 1.27 77 OK
7.87 1.84 4.19
293OK 4.72 1.71 1.30
5900K 0.78 0.56 0.34 500°K
2.30 1.64 0.98
540°K 1.84 1.23 0.62
