Structure and magnetic properties of RFe9Mn3 compounds with R=Y, Tb, Dy, Ho and Er

Abstract

Following the discovery of Nd2Fe14B compound [1] which has been treated as the third generation of the rare earth permanent magnets, the Sm2Fe17 carbides and nitrides [2] with the rhombohedral Th2Zn17-type structure, and Nd(Fe,Ti)12 nitrides [3] with the ThMn12type structure have been found possessing excellent intrinsic permanent magnetic properties. So the iron rich rare earth-transition metal compounds (RnTm) become new potential candidates for permanent magnet applications, and the study of these compounds is attracted intensively world wide. To understand the influence of these interstitial atoms it is necessary to first understand better the interactions that are present in the parent compounds. In this letter, the magnetic properties like the Curie temperature and the saturation magnetization in RFe9Mn3 (R = Y, Tb, Dy, Ho and Er) compounds have been investigated. The mean-field constants of DyFe9Mn3 and HoFe9Mn3 compounds have also been calculated. The Mn element has been chosen because it can show some very interesting magnetic behaviors such as large magnetic moment in some compounds. All the RFe9Mn3 samples with R = Y, Tb, Dy, Ho and Er were prepared by argon arc melting from starting materials of at least 99.5% purity. The alloys were melted five times to ensure homogeneity. After arc melting, the polycrystalline specimens were sealed into evacuated quartz tubes and annealed at 1073 K for 50 h and then quenched into water. The phase composition, the structure and the lattice parameters for the RFe9Mn3 compounds with R = Y, Tb, Dy, Ho and Er were determined by means of the X-ray diffraction (XRD) patterns of free powder samples. Fig. 1 shows the X-ray diffraction patterns of RFe9Mn3compounds with R = Y, Tb, Dy, Ho and Er. The lattice constants a, c and the unit-cell volume V are shown in Table I. It can be seen that all of the investigated compounds are single phase and crystallized in ThMn12-type structure. The lattice constants a, c and the unit cell volume V decrease with increasing atomic number from Tb to Er, reflecting the lanthanide contraction. The specific magnetization was measured on free powder with an extracting-sample magnetometer at 5 K