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The low temperature magnetic properties of ytterbium in f.c.c. phase
M. Ribault, Angélique Benoit, J. Flouquet, G. Chouteau
To cite this version:
M. Ribault, Angélique Benoit, J. Flouquet, G. Chouteau. The low temperature magnetic properties of ytterbium in f.c.c. phase. Journal de Physique Colloques, 1979, 40 (C5), pp.C5-391-C5-392.
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JOURNAL DE PHYSIQUE Collogue C5, supplement au n° 5, Tome 40, Mai 1979, page C5-391
The low temperature magnetic properties of ytterbium in f .c.c. phase
M. Ribault, A. Benoit, J. Flouquet
Laboratoire de Physique des Solides, Bat. 510, Universite Paris-Sud, 91405 Orsay, France
and G. Chouteau
Centre de Recherche sur les tres basses temperatures, CNRS BP 166 Centre de tri, 38042 Grenoble, France
Résumé. — Nous comparons les mesures d'orientation nucléaire sous pression faites sur des impuretés 3d dissoutes dans rytterbium aux mesures correspondantes d'aimantation et d'effet de Haas Van Alphen effectuées sur la matrice. Nous posons le problème de la description des impuretés 3d à la transition métal-semiconductrice et celui de l'origine des porteurs de moment magnétique de la matrice.
Abstract. — The nuclear orientation results obtained under pressure for 3d impurities dissolved in the f.c.c. Ytter- bium are compared with magnetization and de Haas Van Alphen experiments performed on the matrix. Open questions are the description of the 3d impurities at the metal semiconductor transition and the origin of the magnetic carriers of the matrix.
We have discussed recently [1] the magnetic pro- perties of face centered cubic (f.c.c.) ytterbium at zero pressure. We present here a short survey of our results and the new measurements that we are performing by nuclear orientation (N.O.) and magne- tization under a pressure P [1].
At zero pressure in an applied field of 70 kOe, the measured effective field (Hefl) on the 3d impurities dissolved in ytterbium is close to that determined
in Zn by Marsh [2] (in Yb, Cr : - 195 kOe ; Mn : - 185 kOe ; Co 15 kOe) [1]. These results are interpreted as a proof of the divalent character of the ytterbium matrix at zero temperature. The linear variation of the magnetization with the applied field, at 4.2 K, is associated with Yb3+ dissolved in the Yb2 + matrix; these Yb3+ have a so called Kondo correlation temperature of the order of 40 K.
1. Pressure effects. — We are studying by N.O. Co and Mn impurities up to 17 kbar (for experimental conditions see [3]).
On manganese impurity, He({ does not vary in a significant way up to 17 kbar and the result is the same for the Co impurity up to 12 kbar. And so the open question is what is happening when the ytter- bium matrix undergoes the metal-semiconductor transition at 11 kbar ?
For the intermediate range we refer to the de Haas Van Alphen measurements of Ribault, they were interpreted as due to cylindrical pieces of Fermi surface which are characterized by quite high effective masses (m* ~ m0) almost independent of the pressure
in the range 4.6 to 6 kbar; the main conclusion is that the electronic density of states and consequently the 3d impurity parameters do not vary with the pressure in the metallic phase. This is in excellent agreement with our N.O. results.
At higher pressure in the semiconductor phase, a naive picture should be that the 3d parameters are very near the value known in insulator
(HM(Mn) 600 kOe, //eff(Co) > 200 kOe) with respect to the very low electronic density of states. The experimental observation is far from these expected behaviour. Two explanations can be given i) the pressure is not really sufficient. (That objection is ruled out for the Mn impurity where the experi- ments are performed up to 17 kbar) ii) the 3d impurity in the semiconductor phase is not really sensitive
Fig. 1. — Temperature dependence of the magnetization of our f.c.c. Ytterbium sample for an applied field of 100 kOe.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19795142
C5-392 M. RIBAULT, A. BENOIT, J. FLOUQUET AND G. CHOUTEAU
to the matrix either for a fundamental basis of the 3d situation in a semiconductor with 4f levels or for the presence of other impurities always present at a concentration near 1 000 ppm in the original lattice.
The magnetization measurements performed at p > 3 kbar show a large decrease of the deduced susceptibility as is reported on figure 1.
The magnetization shows a flat dependence at a temperature more than three times higher with a value a little bit less than a factor three from the zero pressure determination.
Discussion. - In ref. [l] we discuss the possible origin of Yb3+ and show that the effect of defects should be relaxed by the creation of smaller diameter
ions. The point we want to emphasize is that the number of electronic carriers determined from conduc- tivity measurements is of the same order of the number of Yb3
+.
The band calculation 141 predict that the f.c.c. ~ b matrix is a semiconductor and so the + ~ question is : is ytterbium conductivity due to Y b + 3 creation ? In that picture the limitation of the number of Yb3+ is due to the interactions between them, this is the same situation than the dilution of 3He in 4He at zero temperature. In ytterbium the situation is different from that in a dilute alloy density of states, number of Yb3+ and so called Kondo temperature are closely connected. When pressure is increased the increase of T, shows that the exchange increases and so does the localisation that is the way to semi- conductor transition...
References
[I] RIBAULT, M., BENOIT, A., FLOUQUET, J. and CHOUTEAU, G., J. Phys. F 8 (1978) L-145.
[2] MARSH, J. D., Phys. Lett. 33A (1970) 207. Thesis Oxford, unpublished (1972).
[3] RIBAULT, M., BENOIT, A., TO be published in the L.T. 15 pro- ceedings. J. Physique Colloq. 39 (1978) C6- .
[4] JOHASEN, G. and MACKINTOSH, A. R., Solid State Commun. 8 (1970) 121.
