The magnetization up to 120 T and 10 kbar and magnetostriction up to 40 T have been measured for single-crystalline. Ce(Col _xNix)5 with x ~< 0.3. The Co ...
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Physica B 237-238 (1997) 487-488
Anomalous magnetic properties due to Co metamagnetism in Ce(COl-xNi )5 M.I. Bartashevich a'*, T. Goto a, K. Koui a, K. Kamishima a, A.V. Korolyov b, A.S. E r m o l e n k o b "ISSP, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan blnstitute of Metal Physics, Ekaterinburg 620219, Russian Federation
Abstract
The magnetization up to 120 T and 10 kbar and magnetostriction up to 40 T have been measured for single-crystalline Ce(Col _xNix)5 with x ~/0.1. A metamagnetic transition from the low to the high moment state can be induced by applying field up to 120 T for x = 0.1 and 0.2. The relations between the Co moment state and the magnetic characteristics are discussed. Keywords: Rare-earth-transition-metal compounds; Itinerant metamagnetism; Magnetic moment; Magnetocrystal-
line anisotropy; Ce(Co l_~Nix) 5
RCos compounds crystallize in the hexagonal CaCus-type structure, in which Co atoms occupy two nonequivalent states, 2c and 3g. In RCo5 with trivalent R, the Co m o m e n t Mco, which is produced by the itinerant electrons in 3d band, is well established and reaches, for example, 1.69 #B in LaCo5 [1]. On the other hand, in the compounds with tetravalent Th or Ce, additional electrons supplied by R shift the Fermi level to the higher energy side and the density of states at the Fermi level becomes lower. The magnetization properties of ThCos strongly depend on the Co composition within the homogeneity range of the phase: In the compounds with the low Co content, Mco on the 3g sites is in a low m o m e n t state (LMS) [2]. An applied field added to a large exchange field can produce an itinerant metamagnetic transition of Mco on the 3g site to a high m o m e n t state (HMS). In CeCo5 within homogeneity range, all the Co atoms are in HMS. The substitution of Ni for Co supplies addi* Corresponding author.
tional electrons to the d-band and, as a result, Mco becomes in LMS in Ce(Col -xNix)s for x >/0.1 due to the decrease in the density of d-states at the Fermi level and in the exchange field acting on the Co sublattice [3]. In the present study, the measurements of magnetostriction up to 40 T and magnetization up to 120 T and 10 kbar of single-crystalline Ce(Col_xNi,)5 with x ~< 0.3 have been made to clarify the origin of the transition and its influence on the magnetic properties. The Ce(Col_~Nix)s compounds are highly anisotropic uniaxial ferromagnets. Their main magnetic characteristics are listed in Table 1. The transition of the Co m o m e n t state due to the Ni substitution produces a rapid decrease in Ms, Tc and K1. Fig. 1 shows the magnetization curves of Ce(Coo.9Nio.x)5 along the main axes. A metamag* netic transition from LMS to H M S observed along the c-axis at 21 T shifts to the higher fields along the hard direction (basal plane) by about 25 T due to
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M.L Bartashevich et al. / Physica B 237 238 (1997) 487-488
Table 1 Spontaneous magnetization M~, first anisotropy constant K~, the Curie temperature T¢ and Oln Ms/~ p of the Ce(Col _~Ni~)5 system Ce(Col_xNix)5 M ~ a t 4 . 2 K 0tB/f.u.)
K~ a t 4 . 2 K (K/f.u.)
X =0 0.1 0.2 0.3
63.8 21.0 10.0 5.2
~lnM~/~p T¢ (10 4kbar l)(K)
70 60 5O e-
40 30
(HMS) (LMS) (LMS) (LMS)
7.12 4.35 3.69 2.13
-
18 132 70 82
649 605 582 376
t-L
20 e~
