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.     

Size effects in electrical and magnetic properties of quasi-one-dimensional tin wires in asbestos

Bulk composites have been prepared based on one-dimensional fibers of natural chrisothil-asbestos with various internal diameters (d = 6–2.5 nm) filled with tin. The electrical and magnetic properties of quasi-one-dimensional Sn wires have been studied at low temperatures. The electrical properties have been measured at T = 300 K at a pressure P = 10 kbar. It has been found that the superconducting (SC) characteristics of the nanocomposites (critical temperature T_c and critical magnetic field H_c) increase as the Sn filament diameter decreases. The temperature spreading of the resistive SC transition also increases as the Sn filament diameter decreases, which is explained by the SC order parameter fluctuations. The size effects (the increase in critical temperature T_c and transition width ΔT_c) in Sn nanofilaments are well described by the independent Aslamazov–Larkin and Langer–Ambegaokara fluctuation theories, which makes it possible to find the dependence of T_c of the diffuse SC transition on the nanowire diameter. Using the temperature and magnetic-field dependences of the magnetic moment M(T, H), it has been found that the superconductor–normal metal phase diagram of the Sn–asbestos nanocomposite has a wider region of the SC state in T and H as compared to the data for bulk Sn. The magnetic properties of chrisotil-asbestos fibers unfilled with Sn have been studied. It has been found that the Curie law is fulfilled and that the superparamagnetism is absent in such samples. The obtained results indicate the absence of magnetically ordered impurities (magnetite) in the chrisotil-asbestos matrix, which allowed one to not consider the problem of the interaction of the magnetic subsystem of the asbestos matrix and the superconducting subsystem of Sn nanowires.     

Phase stability,electronic, magnetic and elastic properties of Ni2CoZ(Z = Ga,Sn): A first principles study with GGA method and GGA+U approach

First principles calculations based on density functional theory are used to investigate the phase stability, electronic, magnetic and elastic properties of ferromagnetic metallic full-Heusler Ni₂CoZ(Z = Ga, Sn) alloys via the FP-LAPW method by the generalized gradient GGA and GGA+U approximations for the exchange and correlation energy, within the Perdew–Burke–Ernzerhof (PBE 96) parameterization. The results of calculating electronic structures and magnetic properties reveal that the both Ni₂CoGa and Ni₂CoSn crystallize in L2₁ phase with regular cubic structure. The two investigated compounds exhibit metallic ferromagnetic behaviors for the GGA+U calculation. The computation of elastic constants with GGA+U approach shows that our compounds are mechanically stable.     

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.     

Nb3Sn超导材料的高场钉扎行为

本文利用线性回归分析法处理扩散和气相沉积Nb₃Sn带材样品以及青铜法多芯Nb₃Sn线材样品在高场(²2T)下的临界电流测试数据,得到J_c-B曲线和钉扎力随磁场变化的经验规律。该规律与Kramer模型的钉扎力公式不一致,有待提出新的理论模型加以说明。 关键词：     

Transition probabilities and energy levels in heavy odd-mass isotopes of Sn (A=119–125)

The de-excitation of levels in^119–125Sn populated in the decay of In isotopes has been studied using on-line isotope separators. Level half-lives have been measured in^119–123Sn. a near cancellation of the matrix element for B(E2; g_7/2→ d_3/2) is observed to occur in¹²¹Sn and is probably due to pairing effects. Very low lying 9/2^? levels have been observed in^121–125Sn and are suggested in^{127, 129}Sn. These levels have been interpreted as three quasi-particle states based on the unique parity h_11/2 level. A possible mixing of theg _7/2 level with a close lying 7/2⁺ three quasi-particle state in¹²³Sn is discussed. Radioactivity.^119–125In from²³⁵U(n, f) and²³⁸U(α, f), isotope separated sources; measuredE _γ ,I _γ , E_ce, I_ce,γγ-coin,Βγ-delay, deduced multipolarities.^119–123Sn deduced levels,I, π, B(λ). Ge(Li), Si(Li), NaI(Tl) and plastic detectors, Ge(Li)-Ge(Li) coin, plastic detector — NaI(Tl) delay.     

The effect of compound addition Dy2O3 and Sn on the structure and properties of NdFeNbB magnets

NdFeNbB with the additions of Dy₂O₃ and Sn permanent magnets have been attained by means of powder-blending technique, and their magnetic properties, temperature performance and microstructure were studied in this paper. The addition of just 2.0 wt% Dy₂O₃ or 0.3 wt% Sn proved to be very effective in improving the permanent magnetic properties of NdFeNbB magnets. Dy₂O₃ additions result in the increase in the H_ci and temperature dependence due to the increase of T_c, formation of (NdDy)-rich phase and grain refinement of Φ phase. This improvement of the coercivity stability of the magnets from the addition of Sn is attributed to the smoothing effect of the Sn addition at the grain boundaries. The magnetic properties, the temperature dependence and Curie temperature of NdFeNbB with Dy₂O₃ and Sn combined addition were found to be considerably improved. From the X-ray diffraction, SEM-EDAX studies and the thermo-magnetic study, the improved properties due to the solution of Dy and Sn to the Φ phase, the reduced N_eff and the smaller Φ phase.     

Magnetic properties of TbMn6Sn6-xGax (x=0.0－1.2) compounds

Effects of Ga substitution for Sn on the structure and magnetic properties of TbMn₆Sn_6-xGa_x (x=0.0－1.2) compounds have been investigated by means of x-ray diffraction, magnetization measurement and ¹¹⁹Sn M?ssbauer spectroscopy. The substitution of Ga for Sn results in a decrease in lattice constants and unit-cell volumes. The magnetic ordering temperature decreases monotonically with increasing Ga content from 423 K for x=0.0 to 390 K for x=1.2. At room temperature, the easy magnetization direction changes from the c-axis to the ab-plane. This variation implies that the substitution of Ga for Sn leads to a decrease in the c-axis anisotropy of the Tb sublattice. An increase in the non-magnetic Ga concentration results in a monotonic decrease of the spontaneous magnetization M_s at room temperature. Since there are three non-equivalent Sn sites, 2c (0.33, 0.67,0), 2d (0.33, 0.67,0.5) and 2e (0,0,0.34) in the TbMn₆Sn_6-xGa_x compounds, the ¹¹⁹Sn M?ssbauer spectra of the TbMn₆Sn₆ and TbMn₆Sn_5.4Ga_0.6 compounds can be fitted by three sextets. The hyperfine fields (HFs) decrease in the order of HF(2d)>HF(2e)>HF(2c), which is in agreement with the magnetic structure.     

Nb3Sn超导电磁铁

本文报导了关于筒形Nb₃Sn磁体的研究结果。观察到磁通跳跃现象。“冻结”场的分布和历史及激发场的分布紧密相关。“冻结”场可以不是中心对称的,这进一步证明了烧结的Nb₃Sn材料是非均匀介质。我们描述了新的磁体结构,避免了磁通跳跃。除利用铁心来捕获磁通外,在激发和测量磁场的方法上均具有一定的特点。利用圆筒状Nb₃Sn作为压挤磁通的活塞,在1.5°K时,曾获得的最高场强是28.5KG。     

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     

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.     

A Mössbauer study of FeSn2 at 100 K in applied fields

⁵⁷Fe and¹¹⁹Sn Mössbauer spectra have been recorded at 100 K in applied fields of 32 and 64 kG on a FeSn₂ sample obtained by arranging single crystal needles side by side. The present work confirms that the Sn fields are anisotropic above T_t=93 K. The field model has been used to determine the magnetic structure of FeSn₂ below T_t.     

Magnetic and electronic properties of Mn2Sn thin films: First-principles calculations and high temperature series expansions

In this paper, first-principles calculations have been performed in order to study the electronic and magnetic properties of the bulk and the (0 0 1) surface of Mn₂Sn thin films using self-consistent ab initio calculations, based on the density functional theory approach and using the product of the muffin-tin radius and the maximum reciprocal space vector, R_MT. K_max, we full potential linear augmented plane wave methods. Spin-polarized calculations within the framework of density-functional theory are a powerful tool for describing the magnetism of itinerant electrons in solid state materials. The total and partial density of states of Mn₂Sn thin films were calculated. The magnetic moments considered to lie along the c axes are computed. The data obtained from the ab initio calculations are used as an input for the high temperature series expansions calculations used to compute other magnetic parameters. The critical temperature and exchange interactions between the magnetic atoms in the Mn₂Sn thin films are obtained using high temperature series expansions and mean field theory, respectively.     

Magnetic properties of the mixed spinel Co1+xSnxFe2−2xO4

The structural and magnetic properties of the mixed spinel Co_1+xSn_xFe_2?2xO₄ system for 0.1≤x≤0.5 have been studied by means of X‐ray diffraction, magnetization, a.c. susceptibility and Mössbauer effect measurements. X‐ray intensity calculations indicate that Sn⁴⁺ ions occupy only octahedral (B) sites replacing Fe³⁺ ions and the added Co²⁺ ions substitute for A‐site Fe³⁺ ions. The lattice constants are determined and the applicability of Vegard's law has been tested. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at tetrahedral (A) and octahedral (B) sites for x≤0.4. The Mössbauer intensity data show that Sn possesses a preference for the B‐site of the spinel. As expected, the hyperfine field and Curie temperature determined from a.c. susceptibility decreases with increasing Sn content. The variation of the saturation magnetic moment per formula unit measured at 77 and 300 K with Sn content is satisfactorily explained on the basis of Néel's collinear spin ordering model for x=0.1–0.4.     

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.     

<Superscript>119</Superscript>Sn Mössbauer studies on ferromagnetic and photocatalytic Sn–TiO<Subscript>2</Subscript> nanocrystals

Diluted Sn doped TiO₂ nanocrystals (Sn/Ti ratio: x ≤ 1.37 %) were synthesized by a simple hydrothermal method using pure reagents without any surfactant and dispersant material. The XRD of these samples showed an anatase phase, anatase and rutile mixed phases, and a rutile phase of TiO₂ and SnO₂ with the increase of Sn dopant concentrations. ¹¹⁹Sn Mössbauer spectra gave the broad peaks, which were decomposed into doublets and sextets because almost all these samples showed magnetic hysteresis even at room temperature. The titanium oxides doped with x ≤ 0.12 % showed the relatively large magnetic hysteresis and high photocatalytic activity. Mössbauer spectra of samples doped with x > 0.3 % were analyzed by one doublet and two sextets although the samples showed weak ferromagnetism. Three kinds of Sn species may be distinguished as Sn ⁴⁺ substituted TiO₂ and two different magnetic arrangements of Sn doped TiO₂: one with more oxygen defects and other at the interface of TiO₂ and precipitated SnO₂ containing Ti atoms. The correlation between various amounts of Sn sites and photocatalytic activity and/ or magnetic property was discussed.     

Magnetic structure of the GdAl3 intermetallic compound as seen via Mössbauer spectroscopy data for 119Sn impurity atoms

The magnetic hyperfine interaction for ¹¹⁹Sn impurity atoms in GdAl₃ frustrated antiferromagnetic compound has been investigated by Mössbauer spectroscopy technique. Two magnetic subspectra with the ratio of the intensities 2:1 were observed. At 4.5 K, the values of the magnetic hyperfine field are 4.00(2) and 1.35(2) T. The peculiarities of the Mössbauer spectrum provide an opportunity to propose a plausible model of the spin arrangement in the GdAl₃ lattice. In each GdAl₃ basal layer, the magnetic moments of the Gd atoms form three-sublattice 120° spin structure that is peculiar to magnetically frustrated compounds. The appearance of two magnetically nonequivalent Sn sites is a result of vector summation of the transferred polarizations from Gd moments located in two adjacent GdAl₃ planes. The anomalous temperature behavior of the hyperfine field is characteristic of frustrated systems with competing exchange interactions.     

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