Magnetic hyperfine fields acting on diamagnetic119Sn impurity in rare-earth-3d transition metal laves phases,crystallized under high pressure

A summary of the magnetic and the electronic properties of Laves Phases compounds RT₂ (R=Sm-Lu; T=Fe, Co, Ni) synthesized under high pressure is presented. The hyperfine fields acting on tin impurity nuclei in RT₂ have been obtained by Mössbauer spectroscopy. It has been found that hyperfine fields at¹¹⁹Sn and their temperature dependences for the RFe₂ (R=Sm-Ho), the RCo₂ (R=Sm-Tb) and GdNi₂ prepared at high and atmospheric pressures, are substantially different, respectively.     

Mössbauer measurement of the hyperfine magnetic field AT sp site in Heusler alloys Rh2 Mn Z (Z=In and Sb)

We have investigated the systematics of hyperfine magnetic field on a fixed probe at the Z-site in Heusler alloys Rh₂MnZ as the valence of Z (sp element) is varied. The hmf on¹¹⁹Sn in Rh₂MnIn_.98 ¹¹⁹Sn₀₂ has been measured at 293K and 77K. In Rh₂Mn_1.12Sb_.86 ¹¹⁹Sn_.02 the hmf on¹²¹Sb has been measured at 77 K, and on¹¹⁹Sn at 293 K and 77 K. The results are compared with the hmf on¹¹⁹Sn in Rh₂Mn Ge_.98 ¹¹⁹Sn_.02 Rh₂Mn Sn, and Rh₂Mn Pb_.98 ¹¹⁹Sn_.02.Supported by the University Research Council, University of CincinnatiSupported by the Natural Sciences and Engineering Research Council of Canada     

Effet Mössbauer sur les noyaux d'impuretes 119Sn4+ dans la matrice de VO2

The phase transition in VO₂ doped with 0.16 at.% Sn⁴⁺ was investigated by Mössbauer spectroscopy of ¹¹⁹Sn. Hyperfine magnetic fields were observed on ¹¹⁹Sn nuclei below the transition temperature. At 77 K the maximum hyperfine magnetic field was found to be H(0)_{77 K} = 120 ± 10 kOe The results obtained are discussed in terms of fine antiferromagnetic particles.     

High pressure studies of magnetic, electronic, and local structure properties in the rare-earth orthoferrites RFeO3 (R = Nd, Lu)

The high pressure modification of the electronic structure, magnetic properties, and local crystal structure have been studied in the rare-earth RFeO₃ (R=Nd, Lu) orthoferrites in both pure single crystals and polycrystalline samples doped with Sn. The pressure dependences of the unit cell parameters, Néel temperatures, supertransferred hyperfine magnetic fields at tin nuclei H ^Sn, and the optical absorption edge have been obtained. The relations of the obtained values with the geometry of exchange interactions were analyzed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tin-doped spinel-related oxides of composition M3O4 (M = Mn, Fe, Co)

Tin-doped compounds of spinel-related M₃O₄ (M = Fe, Mn, Co) have been studied by ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectroscopy in the temperature range of 20–600 K. The ¹¹⁹Sn Mössbauer spectra recorded down to 20 K from the non-iron-containing compounds of Co₃O₄ and Mn₃O₄ contained only doublets showing no transfer of magnetic properties from cobalt or manganese to the dopant tin ions. In contrast, the tin-doped-(FeCo)₃O₄ and (FeMn)₃O₄ gave ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectra, which showed magnetic hyperfine interactions. The Curie temperature has been estimated for the former sample.     

119Sn Mössbauer spectroscopy of U x Th1−x CoSn and UCoAl1−x Sn x

Magnetization and¹¹⁹Sn Mössbauer spectroscopy studies were performed on two pseudoternary systems, namely U _x Th_1?x CoSn and UCoAl_1?x Sn _x . Magnetic hyperfine fields on¹¹⁹Sn nuclei were found to be due to local surrounding of U atoms which carry magnetic moments. In pure UCoSn the valuesB _hf=8.66 T and μ_∪ satisfy the relationB _hf=6.75 μ_B found for a number of UTX compounds studied. Local surrounding effects are indicated by multicomponent spectra obtained for the two pseudoternary series.     

Magnetic hyperfine fields on119Sn nuclei in uranium compounds

119Sn Mössbauer spectroscopy studies were performed on 12 uranium intermetallic compounds in order to investigate correlations between the formation of the magnetic moment on the U atom and the magnetic hyperfine field transferred to 119Sn nuclei in magnetically ordered materials. The measured hyperfine fields (H_hf) are related to the values of the ordered U magnetic moments (UB) by U_oH_hf/n=A UU. The parameter A varies between 0.73 (UGa2) and 1.55 (UGe2). It seems to correlate with the extent of the hybridization of the 5f states with the conduction electron states.     

A 57Fe and 119Sn Mössbauer study of BaFe4Sn2O11

The Mössbauer spectrum of BaFe₄Sn₂O₁₁ has been recorded for both ⁵⁷Fe and ¹¹⁹Sn isotopes at a variety of temperatures. In the paramagnetic state the ⁵⁷Fe spectra are interpreted in terms of three iron environments. Magnetic ordering begins at 77 K and is virtually complete by 4.2 K to give an average magnetic hyperfine field of 504 kG. The ¹¹⁹Sn spectra also reflect the magnetic ordering and a magnetic hyperfine field of 45 kG is transferred to the tin nuclei.     

Magnetic hyperfine fields in Heusler alloys Co YZ (Y=Ti,Zr; Z=Al,Ga,Sn)

Magnetic hyperfine fields (mhf) acting on Ta at the Ti and Zr sites have been measured in Heusler alloys Co₂TiAl(Ga,Sn) and Co₂ZrAl(Sn) by the TDPAC technique utilizing the 133–482 keV gamma cascade in¹⁸¹Hf. Curie temperatures of all the alloys have also been measured using a vibrating sample magnetometer. Present data together with the existing results on the Co₂HfAl(Ga,Sn) are discussed and compared with the mhf systematics in Heusler alloys.work partially supported by CNEN and CNPq     

Magnetic hyperfine fields of vacancy-associated119Sn in ion-implanted nickel

Magnetic hyperfine fields of¹¹⁹Sn impurity defects in nickel have been investigated by Mössbauer emission spectroscopy. Radioactive¹¹⁹Xe isotopes were implanted, annealing was performed after¹¹⁹Xe had decayed to¹¹⁹Sb. At least five different components with well-defined magnetic hyperfine fields, isomer shifts and Debye temperatures are identified in the rather complex spectra. One of these (B=2T) is known to be due to substitutional Sn. The hyperfine fields of the other components are pronouncedly larger (B=9T, B=15T, and B=17T, respectively, for single crystals). These defects are proposed to be Sn-multivacancy defects.     

Magnetic hyperfine structure of 119Sn in ferromagnetic Pd2MnSb

A magnetic hyperfine field of H = + 210 ± 5 kOe has been observed at Sn in Pd₂MnSb_0.99Sn_0.01 by Mössbauer spectroscopy on ¹¹⁹Sn. The significance of this measurement with respect to other hyperfine fields and theoretical calculations is discussed.     

Study of hexagonal R-type BaFe4Sn2O11 by57Fe and119Sn Mössbauer spectroscopy

Mössbauer data have been obtained from both the⁵⁷Fe and¹¹⁹Sn isotopes for BaFe₄Sn₂O₁₁. Variable temperature studies show that magnetic ordering occurs at 77K and is probably complete at 4K. Average hyperfine fields of 504kG and 45kG were observed at the iron and tin nuclei respectively.     

Hyperfine anomalies of Sc isotopes (A = 44, 44 m, 46 and 47) in iron

Nuclear magnetic resonance on oriented nuclei (NMR-ON) on Sc isotopes (A = 44, 44 m, 46, 47) in Fe were performed. Using the known magnetic moments the magnetic hyperfine fields were determined. The hyperfine anomalies of various Sc were deduced; ⁴⁴Δ⁴⁷ = 0.0 (12) %, ^44mΔ⁴⁷ = 1.2 (4) %, ⁴⁶Δ⁴⁷ = 2.7 (8) %. The measured hyperfine anomalies are briefly discussed based on the shell model.     

99Ru,61Ni,57Fe,and119Sn Mössbauer studies of Heusler alloys containing ruthenium

⁹⁹Ru,⁶¹Ni,⁵⁷Fe and¹¹⁹Sn Mössbauer spectroscopic studies were made on ternary intermetallic compounds containing ruthenium, Ru_xY_3?xZ (Y=Fe, Ni; Z=Si, Sn). In the system of Ru_xFe_3?xSi, two different hyperfine magnetic fields were observed at the⁹⁹Ru nuclei (H _hf[Ru]) in the range ofx≤1.0 and the magnitude of eachH _hf[Ru] was found to decrease with an increase in the ruthenium concentrationx. Both the⁹⁹Ru and¹¹⁹Sn Mössbauer spectra of Ru₂FeSn could be analyzed with two sets of magnetically split lines. The⁶¹Ni Mössbauer spectra of Ru₂NiSn were obtained at 5 and 77 K.     

Mössbauer study of 119Sn hyperfine interactions in the KTi1−x SnxOPO4 system

The first Mössbauer study of hyperfine interactions of ¹¹⁹Sn nuclei in the complex ferroelectric oxides KTi_1?x Sn_xOPO₄ is reported. A one-to-one correspondence between the hyperfine interaction parameters and tin atom arrangement in cis and trans positions of the structure has been established. The electric-field gradient at ¹¹⁹Sn nuclei is shown to be dominated by the contribution of valence electrons in the hybridized p and d orbitals. A linear correlation between the quadrupole displacement of the spectrum components and the average Sn-O distances has been revealed. The Mössbauer line shift data were used to estimate the number of valence s electrons of Sn⁴⁺ ions occupying the cis and trans positions throughout the x range covered.     

Magnetic hyperfine interactions and compositional short range order in the Heusler alloys Cu2MnIn1-xSnx

A comprehensive study of the magnetic hyperfine interactions and the processes of crystallographic ordering in the Heusler alloy system Cu₂MnIn_1-xSn_x has been made. We report the results of Mössbauer effect experiments, X-ray diffraction studies, electrical transport, and Curie temperature measurements. By a rapid quenching, low temperature annealing technique we have been able to extend the ordered L2₁ structure to high Sn concentration. Observations of inequivalent Sn sites and nonunique ¹¹⁹Sn hyperfine field values in these alloys are shown to be due to difficulties in ordering the L2₁ structure and a basic instability of this phase for high Sn concentrations. The compositional variation of ¹¹⁹Sn hyperfine fields in the ordered L2₁ phase of the Cu₂MnIn_1-xSn_x system reveals a systematic increase with Sn composition. Calculations of these fields based on a homogeneously spin polarized electron gas model reproduce the observed field systematics quite well. The implications of these results on the nature of magnetic interactions in Heusler alloys are discussed.     

Local magnetic structure and anomalies of magnetic hyperfine interactions of57Fe and119Sn nuclei in lithium aluminium ferrites

The⁵⁷Fe and¹¹⁹Sn Mossbauer spectra of ordered ferrites Li_0.5Fe_2.5−xAl_xO₄∶Sn for 0.8<x<1.0 (the compensation point region) have been studied. The spin glass type magnetic structure with the spin canting angle depending on temperature and aluminium concentration is established. Anomalies in the temperature dependence of the hyperfine magnetic field at tin nuclei have been found near the compensation point of the ferrites     

Magnetic hyperfine fields at Fe,Cd and Sn sites in an FeCo alloy

The magnetic hyperfine field at an Fe site in the ferromagnetic alloy Fe_0.475Co_0.525 was measured using the Mössbauer effect. The value obtained at room temperature was 343 kOe. The hyperfine field at a substituted Cd impurity was measured by the method of time differential perturbed angular correlations. A single frequency was observed at room temperature, corresponding to a field of -177 kOe. Using the Mössbauer effect, the Sn site hyperfine field was measured in a sample in which 0.3 atomic percent of ¹¹⁹Sn had been substituted. The room temperature spectrum consisted of the superposition of a single line, together with a six-line hyperfine spectrum, corresponding to a field of 231 kOe. A phenomenological interpretation is proposed for Fe, Cd and Sn fields in the binary alloys of iron.     

Hyperfine Interaction of 111Cd in Fe3Sn Compound

The hyperfine interaction of ¹¹¹Cd in ferromagnetic Fe₃Sn compound was investigated by TDPAC in the paramagnetic region and below the Curie temperature. The results are compared with hyperfine magnetic fields and EFGs on ¹¹¹Cd and ¹¹⁹Sn in other stoichiometric Fe–Sn phases. This revised version was published online in September 2006 with corrections to the Cover Date.     

Magnetic properties and 119Sn hyperfine interaction parameters of LiMn6Sn6

We have synthesized LiMn₆Sn₆, the first RMn₆Sn₆ compound involving an alkali metal as R element. It crystallizes in the hexagonal (P6/mmm) HfFe₆Ge₆-type structure. From magnetic measurements and powder neutron diffraction experiments it is found that LiMn₆Sn₆ magnetically orders at T_C = 380 K in a simple easy-plane ferromagnetic structure (m_Mn = 2.58 μ_B at 2 K). The ¹¹⁹Sn M?ssbauer spectrum recorded at 5 K indicates that the tin nuclei experience huge hyperfine fields (as large as 35 T). Electronic structure calculations are used to gain information about the microscopic origin of both the hyperfine field and electric field gradient at the Sn nuclei. The former arises due to spin-dependent hybridization between the 5s states of Sn and the 3d states of Mn. The latter comes from the 5p charge density close to the nucleus, whose anisotropy is mainly produced through directional interactions with the 3d states of the first Mn neighbors. Comparison between experimental quadrupole splittings and theoretical electric field gradients allows us to propose a value of for the quadrupole moment of the first excited state (I= 3/2) of the ¹¹⁹Sn nucleus.