Structure and magnetic properties of R4(Co,Ti)41 (R= Gd, Pr, Sm) alloys

Margarit Gjoka 2Charalambos Sarafidis 1Orestis Kalogirou 1Dimitris Niarchos 2

1. Dept. of Physics, Aristotle University of Thessaloniki, 54 124 Thessaloniki, Greece, Thessaloniki 54 124, Greece
2. Institute of Materials Science, NCSR “Demokritos”, 153 10 Ag. Paraskevi, Attiki, Greece, Athens 153 10, Greece

Abstract

Nd3(Fe,Ti)29-type structure, widely studied during the last years, consists of a combination of Th2Zn17 (2:17) rhombohedral and ThMn12 (1:12) tetragonal segments in a ratio of 1:1. The existence of this composition indicates that more intermediate phases should be possible: e.g. a ratio 1:2 resulting to a 4:41 phase. The synthesis of a new phase with nominal composition Tb4(Fe,Si)41 has been recently reported [1]. In a previous work we have investigated the alloys with starting nominal composition R4(Fe,Ti)41 (R=Nd, Er; T=Ti, V) [2]. In this work we extend the previous study for the R4(Co,Ti)41 alloys (R=Gd, Pr, Sm). Alloys with starting composition R4(Co1-xTix)41 (x=0.037, 0.051, 0.061) were prepared and annealed in the temperature interval of 1133-1438 K. Thermomagnetic analysis (TMA) for the samples annealed at 1133 K showed one magnetic transition at 1025 K and 1058 K respectively for Gd (x=0.051) and Pr (x=0.037) which, according to the X-ray spectra, correspond to the disordered CaCu5-type structure. The saturation magnetization, MS, of the first samples is 77.3 Am2/kg at room temperature and both exhibit uniaxial anisotropy. The Gd4(Co,Ti)41 (x=0.051) alloy annealed at 1438 K crystallizes into the disordered 2:17 hexagonal phase with cell parameters a=8.350(1) and c=8.224(1) angstrom. In contrary, the Pr4(Fe,Ti)41 samples annealed at 1438 K crystallize into the rhombohedral 2:17R-type structure. The study of the magnetic properties and of the microstructure of this series is in progress and will be reported.

1. Ivanova, G.M. Makarova, Ye.V. Shcherbakova and Ye.V. Belozerov, J. Alloys Compounds 309 (2000) 141.

2. M. Gjoka, D. Niarchos, C. Sarafidis and O. Kalogirou, Proceedings of 17th International Workshop on Rare-Earth Magnets and their Applications, pp. 216-220 (2002).

Presentation: poster at E-MRS Fall Meeting 2005, Symposium B, by Margarit Gjoka
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-12 13:41
Revised:   2009-06-07 00:44
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