Isothermal Section Of GD-MN-SN Ternary System At450℃and The Structure And Magnetic Properties Of The Compound Gd₄Mn_4.8Sn_6.2

In this work, the isothermal of Gd-Mn-Sn ternary system at450℃has been investigated through experimental method. Rietveld refinement from X-ray power diffraction and magnetic measurements were performed for Gd4Mn4.8Sn6.2.Alloy samples of Gd-Mn-Sn ternary system were prepared by the electric arc melting. The phase relations of Gd-Mn-Sn ternary system at450℃has been determined by X-ray power diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results showed that this isothermal section consists of20single-phase regions,41tow-phase regions and22three-phase regions. The existences of twelve binary compounds and two known ternary intermetallic compounds, GdMn2, Gd6Mn23, GdMn12, Gd5Sn3, Gd5Sn4, Gd11Sn10, GdMnxSn2, Gd3Sn7, GdSn3, Mn3Sn, Mn3Sn2and MnSn2, GdMn6Sn6, Gd4Mn4+xSn7-x were confirmed. Two new ternary compounds GdMnSn2, Gd117Mn52Sn112were found. The orthorhombic Gd4Sn11phase was found in alloys annealed at200℃for seven weeks only. The binary phases GdSn2, Gd11Sn10, Gd5Sn4and Gd5Sn3show certain solid solubility of Mn. The maximum solid solubilities are5.0at.%,8.0at.%,7.0at.%and6.0at.%, respectively, the solid solubility of Gd4Mn4+xSn7-x is x=0.35-0.80. It is found in this work that the reported ternary compound GdMno.2Sn2is in the solid solution region of GdSn2, namely GdMnxSn2(x=0-0.16).The automatic indexing of the XRD data for the compound Gd4Mn4.8Sn6.2in the solid solution Gd4Mn4+xSn7-x (x=0.35-0.80) showed that the ternary compound Gd4Mn4.8Sn6.2belong to tetragonal crystal system, lattice parameter a=15.01697(2) A, c=5.942(2) A, V=1340.16A3, and reliable factor F30=43.9. The results of Rietveld refinement showed that the ternary compound Gd4Mn4.8Sn6.2is tetragonal with Zr4Co4Ge7type structure,space group I4/mmm(No.139), lattice parameter a=15.00640(4) A, c=5.93938(2) A, V1337.502(6) A3, Z=4, and reliability R-factor Rp=9.7, weighted R-factor Rwp=12.8. The crystal structures of new compounds GdMnSn2and Gd117Mn52Sn112are unkonwn.The resaults of Gd4Mn4.8Sn6.2magnetic measurements exhibits compound of Gd4Mn4.8Sn6.2displays antiferromagnetic behaviour at the measured temperature range with a paramagnetic Curie temperature of-49.7K, and an effective magnetic moment of16.7μB·f.u.-1. The field dependence of the magnetization at5K shows an almost linear behaviour, implying the para-or antiferromagnetic nature of the compound.