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.     

Magnetic hyperfine fields at sp-impurities in cobalt and nickel

Hyperfine Interactions - The understanding of magnetic hyperfine fields (B hf) at impurity nuclei in magnetic materials has been a central problem in nuclear solid state physics for the last...     

Magnetic hyperfine fields in ferrigehlenites

Western Canadian cretaceous coal (WC5) and Appalachian carboniferous coal (AC4) are good coking coals, although their rheological properties predict a different behaviour with this respect. According to Mössbauer Spectroscopy, iron-based mineral matters of these coals are very different: WC5 spectrum exhibits chiefly Fe₃O₄ while AC4 contains mainly ferrous silicate and no ferric ion. However the spectra of the ashes exhibit a similarity: they characterize α-Fe₂O₃ with a distribution of particle sizes extended down to some tens of nanometers. Such a dispersion could favour catalytic processes during the low temperature stages of coking.     

Magnetic moments and hyperfine fields at Fe in 3d-transition metals

The magnetic moments and hyperfine fields at Fe sites in 3d-transition metals are calculated using the first principle discrete variational method in local density approximation. Although a large positive moment is retained at each Fe site, the hyperfine fields varied from large negative to large positive values. It is concluded that the absence of Mössbauer magnetic splitting does not necessarily imply the absence of local magnetic moments.     

Magnetic hyperfine splitting in superparamagnetic particles in external magnetic fields

The magnetic hyperfine splitting in Mössbauer spectra of superparamagnetic particles, induced by an external magnetic field, has been calculated. Numerical results have been obtained both for isolated particles with a finite value of the magnetic anisotropy energy constant and for strongly interacting particles. Moreover, analytical approximations are derived. The theoretical results are compared with results of experimental studies of supported α-Fe particles and magnetic particles in ferrofluids.     

Table of hyperfine fields for impurities in Fe,Co, Ni and Gd

All data available in the literature for the impurity hyperfine fields in Fe, Co, Ni and Gd matrices are collected and tabulated. The literature search was carried out for all references listed in Physics Abstracts on papers published till the end of December 1978. The present work is an extension of similar earlier compilations [1–6]. The data are arranged in ten columns as explained below:     

The magnetic hyperfine field at Hg impurities in ferromagnetic Gd

The magnetic hyperfine field at dilute Hg impurities in Gd has been investigated by the conversion electron (e ^–)--time differential perturbed angular correlation (TDPAC) technique. The radioactivities^197m Hg and¹⁹⁹Tl were implanted into Gd foils by means of an isotope separator. TDPAC measurements were performed with the 165 keV-L-conversion electron—134 keV--cascade of¹⁹⁷Hg at different temperatures and with the 334 keV--158 keV-K-conversion electron cascade of¹⁹⁹Hg at 200 K.The regular site occupation probabilities were found to be 15(3)% for an annealed^197m HgGd sample and 29(5)% in unannealed¹⁹⁹TlGd samples.From the magnetic hyperfine interaction frequencies measured for the regular sites at 200 K the magnetic hyperfine fields |H _hf(¹⁹⁷HgGd; 200 K)|=256(13) kG and |H _hf(¹⁹⁹HgGd; 200 K)|=267(7) kG were deduced.On leave from the University of Lisboa, Portugal     

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.     

Magnetic hyperfine field at caesium in iron

We report temperature dependence of nuclear orientation (NO), and the first observation of NMR/ON on Cs in iron.^{132, 136}Cs were implanted at room temperature into polycrystalline and single crystal iron. NO values for the (average) magnetic hyperfine field B_hf (CsFe) are close to 34T, intermediate between the value of 40.7T found in on-line samples made at mK temperatures and the NMR/ON value of 27.8 (2)T. The latter studies. The site/field distribution is briefly discussed. ISOLDE Collaboration, CERN     

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.     

Temperature dependence of hyperfine fields at impurities in metals

A model is developed to account for the spin-densities at dilute non- magnetic impurities in ferromagnetic metals which exhibits a non-linear dependence of the hyperfine field on the host magnetization. The theory is used to calculate the hyperfine field at an interstitial positive muon in gadolinium.     

Magnetic dipole fields at interstitial sites in disordered binary alloys of ferromagnetic crystals

The dipole fields at interstitial sites occupied by positive particles (μ ⁺,p) in f.c.c. and b.c.c. diluted binary alloys of ferromagnetic metals are investigated. The characteristic shapes of the distribution functions of the dipole fields is shown to depend on the interstitial site occupied by the positive particle, and they may give information on the formation of diatomic complexes of the light interstitials with substitutional impurity atoms as well as on the degree of short-range order of the alloy.     

Magnetic hyperfine fields in ultrathin Ni films on Cu(100)

The magnetic hyperfine field was measured at ¹¹¹In(¹¹¹Cd) probe atoms in ultrathin Ni films epitaxially grown on Cu(100) utilizing the perturbed -angular correlation (PAC) method. The behaviour of the hyperfine field as a function of temperature was studied for different film thicknesses ranging from 2 up to 10 monolayers. It was found that the strength of the hyperfine fields as well as the critical temperatures are strongly reduced for thin nickel films and approach the bulk value with increasing film thickness. The orientation of the hyperfine field is discussed.     

The hyperfine field on impurities in Gd

Predictions are given for the hyperfine fields on s-p impurities in Gd.