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INVESTIGATIONS OF THE HYPERFINE INTERACTIONS IN Gd1-x Yx AND Gd1-x Scx ALLOYS BY THE MÖSSBAUER EFFECT FOR 155
Gd ISOTOPE
E. Görlich, K. Łątka, R. Kmieć, K. Tomala
To cite this version:
E. Görlich, K. Łątka, R. Kmieć, K. Tomala. INVESTIGATIONS OF THE HYPERFINE INTERACTIONS IN Gd1-x Yx AND Gd1-x Scx ALLOYS BY THE MÖSSBAUER EFFECT FOR 155 Gd ISOTOPE. Journal de Physique Colloques, 1979, 40 (C2), pp.C2-654-C2-655.
�10.1051/jphyscol:19792227�. �jpa-00218608�
JOURNAL DE PHYSIQUE Colloque C2, supplkment au n o 3, Tome 40, mars 1979, page C2-654
INVESTIGATIONS
OF THE HYPERFINE
INTERACTIONSI N
Gd,-,Yx AND
G d l _ , Sc,ALLOYS BY THE
E.A. Gijrlich, K. d$tka, R. ~mie6'and K. Tomala.
I n s t i t u t e o f Physics, JageZZonian University, Cracow, Poland ' ~ n s t i t u t e o f Nuclear Physics, Cracow, Poland.
Rdsum6.- Des mesures d'absorption rdsonnante ont 6t6 effectudes s u r l S 5 ~ d dans une sdrie d'alliages du gadolinium avec l'yttrium et le scandium. Les diverses contributions au champ hyperfin au site de Gd dans le m6tal ont 6td d6duites des rEsultats obtenus pour Gd I-X X Y
.
Abstract.- Resonance absorption measurements on '"~d nuclei were performed for several alloys of gadolinium with yttrium and scandium. The various contributions to the hyperfine field acting on Gd nuclei in the metallic gadolinium were deduced from the results obtained for Gdl-,YX.
Gadolinium forms continuous solid solutions with weakly magnetic yttrium and scandium metals in the whole range of concentrations. Until now, detailed bulk magnetization measurements /1.2/ as well as some neutron diffraction experiments /3/ have been performed for them. From these investigations it was concluded that alloys with the concentrations up to ca.40 per cent of yttrium and 31 per cent of scandium are ferromagnetic at the liquid helium temperature. For higher concentrations of Y- and Sc- diluents the alloys are antiferromagnetic with the direction of magnetization perpendicular to the c- axis.
This paper presents the MEssbauer effect investiga- tions of Gd,-xYx alloys with x = 0.2, 0.4, 0.6 and 0.8 and Gd,-* Sc, alloys with x = 0.20. 0.31, 0.50 and 0.75.
All alloys were prepared by arc-melting of the re- quired amounts of components and were annealed for 3 days at 800'~ in vacuum. The crystallographic purity was checked by X-ray analysis.
The resonance absorption measurements were carried out using the 86.5 KeV gamma line in l S 5 ~ d with a source of the chemical form of 1 5 5 ~ m 2 ~ n , 0 7 / 4 / . During the measurements the source and the resocan- ce absorbers were kept simultaneously at the liquid helium temperature.
In all investigated alloys the direction of a hyper- fine field and the main axis of an electric field gradient are not parallel, therefore, positions and relative intensities of hyperfine lines were calcu- lated by numerical diagonalization of the hyperfine Hamiltonian. Because of a very poor resolution of
hyperfine lines in l S S ~ d , the shape of the resonance absorption spectra were described by the exact for- mula including the so called transmission integral.
In the fitting procedure any distribution of hyper- fine fields was not taken into account. For antifer- romagnetic alloys the 0 angle between directions of a hyperfine field and the main axis of an electric field gradient was kept constant and equal to 90'.
All results obtained until now are summarized in Table I.
As it is seen from the Table I much better fits to experimental data were obtained for yttrium alloys.
Besides, all fits for scandium alloys require much greater FWHM then for yttrium samples with compara- ble compositions of nonmagnetic diluents.
It proves that the field distribution which should mainly influence the FWHM is much greater in alloys with scandium. The concentration dependence of the hyperfine fields is shown in figure 1 . For Gdl-xYx alloys this dependence is almost linear what makes possible to find values of different contributions
to the hyperfine field acting on '"~d nuclei in metallic gadolinium. If the total hf field is given by the formula;
Hhf (Gd metal) = Hcore + Hze + HEe
where : Hcore is the contribution caused by polari- zation of the s-electron core,
HEe is the contribution to the hf field caused by conduction electrons polarized by own magnetic moment of the gadolinium ion (self polarization term).
H :
, is the contribution to the hf field from the polarization of the conduction
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792227
e l e c t r o n s which a r e p o l a r i z e d by n e i g h b o u r i n g The n o n l i n e a r i t y o f t h e c o n c e n t r a t i o n dependence of g a d o l i n i u m i o n s . t h e h y p e r f i n e f i e l d s i n t h e c a s e of Gdl-xScx a l l o y s and t a k i n g i n t o a c c o u n t t h e u s u a l l y a c c e p t e d f o r Gd i s n o t c l e a r f o r u s and r e q u i r e s a d d i t i o n a l i n v e s - v a l u e s Hcore = -340 kG, Hhf (Gd-metal) = -330 kG t i g a t i o n s .
and from f i g u r e I , Hcore + HFe = -170 kG i t c a n be deduced f o r t h e m e t a l l i c g a d o l i n i u m t h a t H:, = + I 70 kG and ,:H = -160 kG.
T a b l e I : H y p e r f i n e p a r a m e t e r s i n Gd,-xYx and Gd,-xSC, a l l o y s .
h
A l l o y s i i h f ( k ~ 3 f m m / s ) * 0 ( d e g )
x
R e m a r k si s
-
i s o m e r s h i f t s a r e c a l c u l a t e d r e l a t i v e t o t h e 1 5 = E u p d s o u c eR e f e r e n c e s
/ I / Thoburn, W.C., Legvold, S., S p e d d i n g , F.H., Phys. Rev.
110
(1958) 1298/ 2 / Nigh, H.E., L e g v o l d , S . , Spedding. F.H., Beaudry, B . J . , J . Chem. Phys.
41
(1964) 3799 / 3 / C h i l d , H . R . , C a b l e , J . W . , J. Appl. Phys.40
(1969) 1003
/ 4 / C a s h i o n , J.D., Prowse, D.B., Vas, A., 3 . Phys.
C: S o l i d S t a t e Phys.
6
(1973) 2611F i g . 1 : C o n c e n t r a t i o n dependance of t h e h y p e r f i n e m a g n e t i c f i e l d s a c t i n g on 1 5 ' ~ d n u c l e i i n GdlexYx and Gdl-,Sex a l l o y s
