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Submitted on 1 Jan 1971
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STRUCTURAL AND MAGNETIC STUDIES OF THE PSEUDO-BINARY COMPOUNDS (Gd1-xNdx) Co2
G. Primavesi, K. Taylor, I. Harris
To cite this version:
G. Primavesi, K. Taylor, I. Harris. STRUCTURAL AND MAGNETIC STUDIES OF THE PSEUDO-
BINARY COMPOUNDS (Gd1-xNdx) Co2. Journal de Physique Colloques, 1971, 32 (C1), pp.C1-661-
C1-662. �10.1051/jphyscol:19711229�. �jpa-00214056�
JOURNAL DE PHYSIQUE
Colloque C I, supple'ment au no 2-3, Tome 32, Fe'vrier-Mars 1971, page C 1 - 661
STRUCTURAL AND MAGNETIC STUDIES
OF THE PSEUDO-BINARY COMPOUNDS (Gd,-Pd,) Co,
by G. J. PRIMAVESI (*), K. N. R. TAYLOR (*) and I. R. HARRIS (**)
Rksumk.
- Nous avons effectue des mesures d'aimantation et de parametre du reseau pour les compods Gd1-~Nd~Co2. On interprete le comportement magnetique en termes de moment bloqu6 du nbdyme dont l'amplitude varie avec la temp6rature et la composition. On peut mettre en relations les variations de parametre du rkseau et les don- nQs magnetiques.
Abstract. - Measurements have been made of the magnetization and lattice parameters of the compounds Gd I-,NdzCo2. The magnetic behaviour has been interpreted in terms of a quenched neodynium moment whosemagnitude varies with temperature and composition. The changes in lattice parameter may be correlated with the magnetic data.
Introduction. - In the course of a series of inves- magnetization curves. Saturation moment data of tigations into the magnetic properties of compounds figure 1 for less than 50 % neodymium, suggests a and alloys formed with the heavy and light rare earth slightly higher value for the equilibrium concentration metals, and of the effects of magnetic order on the at
x =0.57. A specimen of this composition was lattice parameters of Laves phase compounds, we prepared and gave the magnetization temperature data have examined the pseudobinary series Nd,Gd, -,Co,. given in figure 2. On increasing the temperature the
Experimental.
-The techniques used for speci- men preparation, the determination of lattice para- meters and magnetization measurements have been described previously [I]. Figure 1 shows the variation
I
I
FIG. 1. -
Composition dependance of the room temperature lattice parameters and saturation magnetization at
4.2 OKfor
Gdl-zNdzC02.
with neodymium concentration of the room tempera- ture lattice parameters and the saturation moments a t 4.2 OK. The observed Curie temperatures decrease linearly between those of the terminal compounds (GdCo,
=416OK, NdCo,
=113 OK) to better than 3 %. For neodymium concentrations between x
=0.57 and 0.67 the magnetization-temperature curves exhi- bit compensation points suggesting an equilibrium concentration of x = 0.55. Reversal of the magnetiza- tion was only observed in the variation of remanence with temperature ; for applied fields greater than zero the compensation points appeared as minima in the
(*)
University of Durham.
(**)
University of Birmingham.
Ro.
2.- Temperature dependance of the remanent magne- tization and magnetization at
4kOe applied field for composition
x = 0.57.
observed remanence reversed sign at T = 90 OK and 205OK, as shown in the figure. In an applied field there is a slight minimum in the magnetization at approximately 80 OK but the rapid rise in magnetiza- tion for T > 1000K obscures any feature which may occur near 200 OK.
The lattice parameter variation across the series shows a change in slope at about
x =0.33 and a sudden rise at
x FZ0.57.
Discussion. - Previous workers [2, 31 have shown that the observed molecular moments of the AB, compounds can be understood in terms of an exchange interaction which causes the spins of the rare earth and transition metal ions to be anti-parallel. With the heavy rare earths this leads to a ferrimagnetic structure and with the light rare earths to ferro- magnetism. Use of this model leads to values of the ionic cobalt moment close to 1.0 pB for GdCo, and 0.8 pB for NdCo,. In addition it is frequently neces- sary to invoke a crystal field quenched rare earth
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19711229