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Magnetic properties of the Ce Mn2 [SixGe1-x]2, Ce[Mn1-xFex]2Si2 and Ce[Mn1-xCux]2Si2 compounds
S. Siek, A. Szytula
To cite this version:
S. Siek, A. Szytula. Magnetic properties of the Ce Mn2 [SixGe1-x]2, Ce[Mn1-xFex]2Si2 and Ce[Mn1-xCux]2Si2 compounds. Journal de Physique Colloques, 1979, 40 (C5), pp.C5-162-C5-164.
�10.1051/jphyscol:1979561�. �jpa-00218978�
Magnetic properties of the Ce Mn
2[Si
fGe!_J
2, Ce[Mn!_^FeJ
2Si
2and CelMn^^CuJjSia compounds
S. Siek (*) and A. Szytula (**)
(*) Institute of Physics, Technical University of Cracow, Poland (**) Institute of Physics, Jagellonian University, Cracow, Poland
Abstract. — Magnetic measurements were made for the systems CeMn2[Si;cGe1_J2 and CefMnj.^BJjSij where B = Fe or Cu. In the first system transition from ferromagnetic to antiferromagnetic properties is observed with increasing Si content. In the remaining systems the antiferromagnetic properties are observed belong x < 0.5.
The magnetic phase diagram was constructed.
Intermetallic compounds represented by the formula RB2Si2, where R is a rare earth element and B is a transition metal, are well known and have been extensively studied. These compounds crystallize in the ThCr2Si2 body-centered tetragonal type struc- ture (space group D^-M/mmm). The ions R, B, and Si occupy the 2(a), 4(d), and 4(e) positions of the space group. Magnetic measurements have shown, that CeMn2Ge2 is a ferromagnet with Curie temperature 316 K [1], CeMn2Si2 is a collinear antiferromagnet with Neel temperature 379 K [2], and CeFe2Si2 [3]
and CeCu2Si2 [4] are paramagnets above 4.2 K.
The present paper describes the results of the magne- tic measurements made on the CeMn2[SixGe1_J2, Ce[Mn1_A.FeJ2Si2, and Ce[Mn1_JCCux]2Si2 systems.
The purpose of this work is an observation of changes of magnetic properties with the substitutions of Si for Ge, and Mn for Fe or Cu.
The specimens were prepared by a combination of induction melting and solid state diffusion technique.
The purity was 3N for Ce, 4N for 3d metals, and 5N for Si. All the samples were melted and annealed for three days at 800 °C, and cooled to room tempe- rature. The single-phase nature of the compounds
was established by X-ray analysis using FeKa radia- tion. A least-squares fit to the observed 2 6 values was used to obtain the lattice parameters. The lattice constants of the systems are shown in figure 1. All the a-, c-, K-curves decrease with increase in x content, only the a-curve in Ce[Mn1_x:CuJ2Si2 system rises with increase in Cu content.
The magnetometric measurements were carried out in the temperature range 100-600 K using elec- tronic type balance with a maximum field of 11 kOe.
The temperature dependence of the magnetization and magnetic susceptibility for CeMn2[SixGe1_J2 Fig. 1. — Variation with concentration of the lattice constants and unit cell volume at room temperature.
JOURNAL DE PHYSIQUE Colloque C5, supplément au n° 5, Tome 40, Mai 1979, page C5-162
Résumé. — On a étudié les propriétés magnétiques des systèmes CeMn2(Si;cGe1_J(:)2 et Ce(Mnj_^B )2Si2 où B = Fe ou B = Cu. Dans le premier système CeMn2(Si;<:Ge1_JC)2 on a constaté la transition d'ordre ferromagné- tique à ordre antiferromagnétique en augmentant la concentration de Si. On a observé des propriétés antiferro- magnétiques dans les systèmes avec x < 0,5. Les diagrammes magnétiques de ces composés ont été déterminés.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979561
MAGNETIC PROPERTIES OF THE CeMn2[SixGe, -J,, Ce[Mn, -,Cu,],Si, C5-163 compounds is shown in figure 2. The results of magne-
tic measurements showed that in the
system three concentration regions appear :
- for x < 0.45 the samples have ferromagnetic properties,
Fig. 2. - Results of the magnetic measurements for the CeMn,(Si,Ge, -3, system.
- for 0.45 < x
<
0.7 the samples undergo a transition from the antiferromagnetic (AF) to ferro- magnetic state (F) through a transitional state as the temperature rises. The transition temperatures TI, T,, T, correspond to the transition from AF to the transitional state, from the transitional state to F and from F to the paramagnetic state respectively,- for x d 0.75 the samples have antiferromagnetic properties. A magnetic phase diagram of the system CeMn,[Si,Ge,-,I, derived on the basis of TI, T,, T, determined by the magnetic measurements (in field 11 kOe) is shown in figure 3. To establish precisely the character of the A F to F transition, magnetic measurements in strong pulsed magnetic fields (to 200 kOe) were carried out for CeMn,SiGe ( x = 0.5).
The obtained results show that the A F to F transition occurring in weak fields around 230 K, can be induced at lower temperatures by applying a sufficiently strong magnetic field. The almost linear temperature depen-
Fig. 3, -Magnetic phase diagram of the Ce~n,(Si,Ge,-3, system.
dence of critical field is characteristic of the first order phase transitions.
The results of magnetometric measurements of the Ce[Mnl-,BX],Si2, where B = Fe or Cu show that the compounds with x < 0.5 are antiferromagnetically ordered. The NBel temperature for the
system decrease linearly with Fe concentration. For CeMnFeSi, and CeMnCuSi, additional measure- ments were performed at the temperatures ranging from 4.2 to 300 K using vibrating sample magneto- meter with the maximum field of 50 kOe. Figure 4 presents the magnetic field dependence of magneti-
Fig. 4. - Temperature dependence of the magnetization and reci- procal magnetic susceptibility for CeMnCuSi,(a) and field depen- dence of magnetization for CeMnCuSi, 1 and CeMnFeSi, 2 at temperature 4.2 K.
C5- 164 S. SIEK AND A. SZYTUtA
zation measured at 4.2 K and the temperature depen- at LaCo,Ni, compound [5]. We think that the inter- dence of magnetization in magnetic field H = 10 kOe. pretation of our data can be similar to [5].
Both compounds show metamagnetic type transition
with critical field equal to 12.5 and 6.0 kOe at tempe- Acknowledgments. -Thank is due to Dr. A. Zigba rature 4.2 K respectively. The temperature dependence and Dr. A. Zygmunt for making the magnetometric of magnetization of the CeMnCuSi, is similar to that measurements possible.
References
[I] NARASIMHAN, K. S. V. L., RAO, V. U. S., BERGNER, R. L.
and WALLACE, W. E., J . Appl. Phys. 46 (1975) 4957.
[2] SIEK, S., SZYTULA, A. and LECIEIEWICZ, J., Phys. Status Sohdi (a) 46 (1978) K 101.
[3] FELNER, I., MAYER, I., GRILL, A. and SCHIEBER, M., Solid State Commun. 11 (1972) 1231.
[4] SALES, B. C. and VISWANATHAN, R., J. of LOW Temp. 23 (1976) 449.
[5] BUSCHOW, K. H. J., BROUHA, M. and RIJNBEEK, A. G., Solid State Commun. 16 (1975) 31.
