Roman Kmieć

Crystal and magnetic properties of GdTSn compounds (T = Ag, Au)

Abstract The results of structure, ac and dc susceptibilities, and 119 Sn Mossbauer studies of GdAgSn and GdAuSn compounds are presented. It was found that these compounds order anti-ferromagnetically at T N = 34.3(2) K, and T n = 22.9(2) K, respectively. Additionally a second transition at T f = 15.3(2) K was discovered for both intermetallics. The nature of this second transition is discussed and strong experimental arguments supporting the spin-glass origin and reentrant antiferromagnetic character of the compounds under study are given.

Structure, magnetic properties and {sup 119}Sn Mossbauer spectroscopy of PrRhSn

AbstractPrRhSnwassynthesizedinpolycrystallineformbyareactionofpraseodymium,rhodium,andtininanarc-meltingfurnace.Thesample was investigated by powder and single crystal X-ray diffraction: ZrNiAl type, space group P¯62 m; a ¼ 742:49ð7Þ,c ¼ 415:05ð5Þpm, wR 2 ¼ 0.0737, 353F 2 values and 14 variables. The PrRhSn structure has two crystallographically independentrhodiumsiteswithatricappedtrigonalprismaticcoordination,i.e.[Rh1Sn 3 Pr 6 ]and[Rh2Sn 6 Pr 3 ].Therhodiumandtinatomsbuildup a three-dimensional [RhSn] network with short Rh–Sn contacts (278 and 285pm), in which the praseodymium atoms filldistorted hexagonal channels. The magnetic and electronic properties of PrRhSn have been studied by means of AC and DCmagnetic susceptibility measurements as well as 119 Sn Mo¨ssbauer spectroscopy. A transition from a paramagnetic to aferromagneticstatewasfoundatT C ¼ 3:0K.r 2005ElsevierInc.Allrightsreserved. Keywords: Intermetalliccompound;Magnetism;Mo¨ssbauerspectroscopy 1. IntroductionThe rare-earth metal based stannides RERhSn(RE ¼ rare-earthelement)havethoroughlybeeninves-tigated in recent years [1–5, and references therein].A detailed literature overview is given in [1] and [5].Especially, the valence fluctuations of CeRhSn andthe heavy fermion behavior of YbRhSn are of greatinterest.The crystal chemistry and the physical propertiesof the RERhSn stannides with the early rare-earthelementshavecontroversiallybeendiscussed.ThelatticeparametersforCeRhSn,PrRhSn,andNdRhSnreportedbyRoutsietal.[6]aredifferentfromthosereportedbyMishra et al. [1]. A recent single crystal study of theNdRhSnstructure[7]clearlyconfirmedtheX-raypowderdatagivenin[1].Thetwodifferentstudiesalsorevealedadiscrepancyconcerningthemagneticordering.Whilenohint for magnetic ordering was evident in the originalwork [6], ferromagnetic ordering at T

155Gd and 119Sn Mössbauer effect investigations of GdCuSn and GdAuSn

Abstract 155 Gd and 119 Sn Mossbauer effect measurements were performed on polycrystalline samples of GdCuSn and GdAuSn. The analysis of the gadolinium and tin resonance spectra allowed us to determine the directions of the gadolinium magnetic moments in the crystalline lattice as well as to draw conclusions about the magnetic structure of these materials. Measured quadrupole interaction constants at the gadolinium site give information about the axial coefficient B 0 2 of the crystalline electric field Hamiltonian.

119Sn Mössbauer spectroscopy studies of RAgSn compounds (R=La, Ce, Pr)

Abstract X-ray analysis and detailed 119Sn Mossbauer studies in a wide range of temperatures have been performed on the title compounds. Hyperfine interactions parameters were determined and discussed. The temperature dependence of Mossbauer spectra clearly shows non-magnetic character of LaAgSn compound and the onset of magnetic order for the Ce and Pr systems where the Neel temperatures have been estimated from and compared to those found by other experimental methods. The problem of crystal electric field leading B02 terms and their reference to the magnetic alignment of rare earth (Ce, Pr) moments is considered and confronted with recent neutron studies.

Structure, Chemical Bonding and 119Sn Mössbauer Spectroscopy of LaRhSn and CeRhSn

The rare earth (RE) stannides LaRhSn and CeRhSn were prepared from the elements by arcmelting or by reactions in sealed tantalum tubes in a high-frequency furnace. The structures have been refined from X-ray single crystal diffractometer data: ZrNiAl type, P6̅2̅m, a = 748.74(5), c = 422.16(3) pm, wR2 = 0.0307, 310 F2 values for LaRhSn and a = 745.8(1), c = 408.62(9) pm, wR2 = 0.0397, 354 F2 values for CeRhSn with 14 variables per refinement. The structures contain two crystallographically different rhodium sites which both have a tricapped trigonal prismatic coordination: [Rh1Sn3RE6] and [Rh2Sn6RE3]. Together the rhodium and tin atoms (280 - 288 pm Rh-Sn distances in LaRhSn and 277 - 285 pm in CeRhSn) build up three-dimensional [RhSn] networks in which the rare earth atoms fill distorted hexagonal channels. DFT band structure calculations reveal a large cerium 4 f contribution at the Fermi level and a strong mixing of cerium 5d/4 f with rhodium 4d orbitals. These results are in agreement with the short Ce-Rh bonds (304 and 309 pm) and also with the electronic and magnetic properties. 119Sn Mössbauer spectra of LaRhSn and CeRhSn show a single tin site at isomer shifts of δ = 1.98(2) (LaRhSn) and 1.79(1) mm/s (CeRhSn) subject to quadrupole splitting of Δ EQ = 0.79(4) (LaRhSn) and 1.12(3) mm/s (CeRhSn). The 1.8 K data show no transferred hyperfine field at the tin site for CeRhSn.

Magnetic order in Gd1−xCexCu6, a 155Gd Mössbauer study

Abstract We have studied the influence of Ce-doping upon local properties at Gd sites in Gd1−xCexCu6 by 155Gd Mossbauer spectroscopy. Our primary interest concentrated upon the evolution of the magnetic order of Gd moments and of the electronic density at Gd sites with increasing Ce-concentration. In addition, the variation of magnetic hyperfine fields with temperature yields estimates of the Neel temperature as a function of Ce content x.

Antiferromagnetic Ordering in GdRhIn5

A polycrystalline sample of tetragonal GdRhIn5 (HoCoGa5 type, space group P4/mmm) was obtained by induction melting of the elements in a glassy carbon crucible in a water-cooled sample chamber and subsequent annealing at 670 K. X-ray powder data yielded the cell parameters a = 460.65(7), c = 743.52(12) pm. The magnetic and electronic properties of GdRhIn5 have been studied by magnetic susceptibility, electrical resistivity, and 155Gd Mössbauer spectroscopic measurements. Antiferromagnetic ordering is detected at 41.0(2) K. The results are discussed using a simple molecular field approximation.