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Magnetic properties of some neptunium heavy-fermion intermetallics
650
Journal of Magnetism and Magnetic Materials 76 & 77 11988) 650 North-Holland, Amsterdam
MAGNETIC PROPERTIES OF SOME NEPTUNIUM
HEAVY-FERMION
INTERMETALLICS
J. G A L 1.3 S. F R E D O I, S. T A P U C H I 1 j. JOVE x, M. P A G E S 2, A. C O U S S O N ~, W. P O T Z E L ~, F.J. L I T T E R S T 3, j. M O S E R 3 a n d G.M. K A L V I U S ~ Nuch, ar Engineering Department, Ben-Gurion Unit~ersiO' o1 the Negec and NRCN, Beer-Sheca, lvrael Laboratoire Curie,, Paris. France Plo'sik-Department El5, Teehnische Unieersitdt M~nchen, D 8046 Garching. Fed. Rep. Germa, O"
For the Np intermetallics NpBe13, NpRu 2, Nplr 2, and NpOs2 we find that at low temperatures the followingproportionatitins hold between local (Xk) and bulk susceptibilities (Xu), electronic specific heat y(0) and isomer shift S: Xl = X~ oc ¥(0) c~S. M a n y N p intermetallics, in particular NpB%3 [1] and the Laves phases N p R u 2, N p l r 2 a n d N p O s 2 [2,3] exhibit high coefficients 7 of electronic specific heat. Most of them show magnetic order below 10 K which is p r o b a b l y of itinerant character. The ordered m o m e n t s derived from M/3ssbauer hyperfine fields are considerably reduced compared to the high temperature paramagnetic m o m e n t s [4]. The ordered m o m e n t s a n d the ordering temperatures decrease when external pressure is applied [5]. This is caused by an increase of 5f electron hybridization. The magnetically ordered state is very sensitive to defects and strain produced by variation of stoichiometry a n d a n n e a l i n g history. Magnetic order may even be suppressed [4]. The isomer shifts S (electron density entering the N p nucleus) a n d y are found to be linearly correlated. For the Laves phases this can be traced to a change of 5 f - 5 f overlap. For NpB%3, however, hybridization of 5f electrons with p-electrons of the Be may be d o m i n a n t [4,6]. F r o m the m e a s u r e m e n t of the magnetic hyperfine fields with applied external fields in the p a r a m a g n e t i c state the local susceptibilities Xk can be derived. These are in good agreement with the bulk susceptibilities X u. This means that all m o m e n t s are well located at the N p site. In the low temperature limit we find that in addition the following relation is fulfilled:
x . c~ r ( 0 )
with roughly the same p r o p o r t i o n a l i t y c o n s t a n t for all the investigated c o m p o u n d s . This indicates that the ratios of Stoner factor to mass e n h a n c e m e n t are of roughly the same magnitude.
This work has been funded by the G e r m a n Federal M i n i s t e r for Research and Technology ( B M F T ) u n d e r contracts 0 3 - K A 1 T U M - 4 and 03G A L B E E and by the N a t i o n a l Council for Research and D e v e l o p m e n t ( N C R D ) , Israel.
References
[1] G.R. Stewart, Z. Fisk, J.L. Smith. J.O. Willis and M.S. Wire, Phys. Rev. B30 (1984) 1249. [2] M.B. Brodsky and R.J. Trainor, Physica B 86k88 (1977) 143, B 91 (1977) 271. [3] M.B. Brodsky and R.J. Trainor, J. de Phys. Colloq. 39 (1978) C6-777. [4] J. Gal, F.J. kitterst, W. Potzel, J. Moser, U. Potzel, G.M. Kalvius, S. Fredo and S. Tapuchi, Phys. Rev. B 36 (19871 2457. [5] W. Potzel, J. Moser. U. Potzel, F.J. Litterst, G.M. Kalvius, J. Gal, M. Bogt~, J. Chappert and J.C. Spirlct, Hyperfine Interactions 34 (1978) 391. [6] G.M. Kalvius, J. Gal, F.J. Litterst, W. Potzel, J. Moser, If. Potzel, W. Schiessl, S. Fredo, S. Tapuchi and J.C. Spirlet, J. Magn. Magn. Mat. 70 (1987) 359.
0 3 0 4 - 8 8 5 3 / 8 8 / $ 0 3 . 5 0 © Elsevier Science Publishers B.V.
Journal of Magnetism and Magnetic Materials 76 & 77 11988) 650 North-Holland, Amsterdam
MAGNETIC PROPERTIES OF SOME NEPTUNIUM
HEAVY-FERMION
INTERMETALLICS
J. G A L 1.3 S. F R E D O I, S. T A P U C H I 1 j. JOVE x, M. P A G E S 2, A. C O U S S O N ~, W. P O T Z E L ~, F.J. L I T T E R S T 3, j. M O S E R 3 a n d G.M. K A L V I U S ~ Nuch, ar Engineering Department, Ben-Gurion Unit~ersiO' o1 the Negec and NRCN, Beer-Sheca, lvrael Laboratoire Curie,, Paris. France Plo'sik-Department El5, Teehnische Unieersitdt M~nchen, D 8046 Garching. Fed. Rep. Germa, O"
For the Np intermetallics NpBe13, NpRu 2, Nplr 2, and NpOs2 we find that at low temperatures the followingproportionatitins hold between local (Xk) and bulk susceptibilities (Xu), electronic specific heat y(0) and isomer shift S: Xl = X~ oc ¥(0) c~S. M a n y N p intermetallics, in particular NpB%3 [1] and the Laves phases N p R u 2, N p l r 2 a n d N p O s 2 [2,3] exhibit high coefficients 7 of electronic specific heat. Most of them show magnetic order below 10 K which is p r o b a b l y of itinerant character. The ordered m o m e n t s derived from M/3ssbauer hyperfine fields are considerably reduced compared to the high temperature paramagnetic m o m e n t s [4]. The ordered m o m e n t s a n d the ordering temperatures decrease when external pressure is applied [5]. This is caused by an increase of 5f electron hybridization. The magnetically ordered state is very sensitive to defects and strain produced by variation of stoichiometry a n d a n n e a l i n g history. Magnetic order may even be suppressed [4]. The isomer shifts S (electron density entering the N p nucleus) a n d y are found to be linearly correlated. For the Laves phases this can be traced to a change of 5 f - 5 f overlap. For NpB%3, however, hybridization of 5f electrons with p-electrons of the Be may be d o m i n a n t [4,6]. F r o m the m e a s u r e m e n t of the magnetic hyperfine fields with applied external fields in the p a r a m a g n e t i c state the local susceptibilities Xk can be derived. These are in good agreement with the bulk susceptibilities X u. This means that all m o m e n t s are well located at the N p site. In the low temperature limit we find that in addition the following relation is fulfilled:
x . c~ r ( 0 )
with roughly the same p r o p o r t i o n a l i t y c o n s t a n t for all the investigated c o m p o u n d s . This indicates that the ratios of Stoner factor to mass e n h a n c e m e n t are of roughly the same magnitude.
This work has been funded by the G e r m a n Federal M i n i s t e r for Research and Technology ( B M F T ) u n d e r contracts 0 3 - K A 1 T U M - 4 and 03G A L B E E and by the N a t i o n a l Council for Research and D e v e l o p m e n t ( N C R D ) , Israel.
References
[1] G.R. Stewart, Z. Fisk, J.L. Smith. J.O. Willis and M.S. Wire, Phys. Rev. B30 (1984) 1249. [2] M.B. Brodsky and R.J. Trainor, Physica B 86k88 (1977) 143, B 91 (1977) 271. [3] M.B. Brodsky and R.J. Trainor, J. de Phys. Colloq. 39 (1978) C6-777. [4] J. Gal, F.J. kitterst, W. Potzel, J. Moser, U. Potzel, G.M. Kalvius, S. Fredo and S. Tapuchi, Phys. Rev. B 36 (19871 2457. [5] W. Potzel, J. Moser. U. Potzel, F.J. Litterst, G.M. Kalvius, J. Gal, M. Bogt~, J. Chappert and J.C. Spirlct, Hyperfine Interactions 34 (1978) 391. [6] G.M. Kalvius, J. Gal, F.J. Litterst, W. Potzel, J. Moser, If. Potzel, W. Schiessl, S. Fredo, S. Tapuchi and J.C. Spirlet, J. Magn. Magn. Mat. 70 (1987) 359.
0 3 0 4 - 8 8 5 3 / 8 8 / $ 0 3 . 5 0 © Elsevier Science Publishers B.V.