Study of the magnetic structure and57Fe hyperfine interaction in FeMnP

The⁵⁷Fe Mössbauer spectra of FeMnP show a remarkable magnetic distribution for T 175K, although all iron atoms are crystallographically equivalent. It seems possible to explain this distribution by a spin modulation described by coexistence of an antiferro — and a helimagnetic probe. A theoretical calculation performed, justifies this explanation.     

Quadrupole interaction at57Fe in zirconium metal

The nuclear quadrupole interaction at⁵⁷Fe nuclei in hcp -zirconium metal is measured in the temperature range 4.2 to 560 K using Mössbauer spectroscopy of⁵⁷Fe. The quadrupole splitting at room temperature is measured to be 0.660(8) mm/sec which corresponds to an electric field gradient of |eq|=3.17×10¹⁷ V/cm² at the⁵⁷Fe nucleus in a -Zr host. As has been observed in many other systems, the results show significant electronic contributions. The temperature variation of the quadrupole interaction is much stronger than is expected from the lattice contributions and is found to follow theT ^3/2 dependence approximately.⁵⁷FeZr does not follow the universal correlation betweeneq _ion andeq _el observed in most of the normal metal hosts but follows the trends recently observed by Krusch and Forker for the transition metal hosts. Our results are compared with the predictions of the conduction electron charge shift model recently proposed by Bodenstedt and Perscheid.     

The effect of radiofrequency modulation of 57Fe hyperfine interaction by rotating magnetic field

The effect of ⁵⁷Fe hyperfine interaction radiofrequency (rf) modulation by external rotating magnetic field was studied in thin Permalloy foil by means of Mössbauer spectroscopy. The rf effect was investigated as a function of intensity for several rf field frequencies. The experiments show that the external rotating rf field causes considerable changes in the hyperfine pattern. The obtained spectra are in disagreement with those obtained by Perlow [Phys. Rev. 172 (1968) 319]. They also are inconsistent with magnetostriction hypothesis. Proceeding from the Mössbauer spectrum analysis one may conclude that the magnetization of investigated foil changes its direction in a complex manner. However, the undertaken experiments show that the essential number of Mössbauer nuclei experience the rotating magnetic field influence.     

Temperature dependence of57Fe hyperfine field in Gd: YIG

The NMR spectra of⁵⁷Fe in Gd: YTG polyeryslallaline samples were measured between liquid-helium and room temperatures. In spectra of⁵⁷Fe on tetrahedral sites, beside the main line, weaker and broader peak at higher frequencies appears. It can be decomposed in to the three satellites corresponding to Fe³⁺ ion with one Gd³⁺ ion in the nearest (two satellites) and next nearest dodecahedral site. The temperature dependence of the stellite resonance frequency indicates, that the part of the transferred hyperfine field on⁵⁷Fe with the Gd³⁺ in the nearest c-site depends on the magnetic moment of Gd³⁺ ion. The resonance frequency of the satellite corresponding to the⁵⁷Fe with Gd³⁺ in the next nearest c-site follows the temperature dependence of the dipolar field, the change of the transferred field is small.     

Magnetic hyperfine interaction of 59Fe in nickel

Nuclear magnetic resonance on oriented nuclei (NMR-ON) on ⁵⁹Fe isotope in Ni was performed. The magnetic hyperfine splitting frequency of was determined to be ν(B ₀?=?0)?=?48.32 (2) MHz. Using the known magnetic moment the magnetic hyperfine field was deduced as B _HF?=???28.32 (5) T. The effective nuclear spin-lattice relaxation time was also measured. The measured value is compared with experimental values of 3d-impurity in nickel host.     

Modification of hyperfine field on57Fe nuclei in substituted ferrimagnetic garnets

We review the results of the NMR on⁵⁷Fe nuclei in a number of ferrimagnetic garnets Y_3−x R_xFe₅O₁₂ (R =rare earth or Bi) and Y₃Fe_5−xM_xO₁₂ (M=Al, Ga, In). For suitable concentrations of substituted ions (x∼0.1–0.4) satellite lines in the NMR spectra of both tetrahedral and octahedral Fe ions are observed. These satellites correspond to Fe ions in the vicinity of which single substitution is situated. The splitting between the satellite and the parent line has its origin in the change of the dipolar field and in the change of crystal field effects (including the transfer of electrons). While the dipolar field is easily calculated, once the magnetic moments and the geometry is known, the origin of the change of the crystal field effects is much less clear. Experimental results show that it is anisotropic and that in some cases the anisotropy may be substantial. This anisotropy is discussed within the framework of the semiempirical “independent bond” method.     

Mixed hyperfine interaction in amorphous Fe-Zr sputtered films in external magnetic field — A57Fe Mössbauer study

Conventional⁵⁷Fe-Mössbauer spectroscopy provides only information about the magnitude of the splitting QS in the case of electric quadrupole hyperfine interaction, but not on the sign of the main component of the electric field gradient (EFG), V_zz, or the asymmetry parameter, η, which are sensitive to the local environment of the⁵⁷Fe nuclei. This kind of information is obtained by measurements in external magnetic fields. In the case of amorphous Fe-Zr sputtered films mixed hyperfine interaction leads to a clear change in the behaviour of the Zr-rich and the Fe-rich alloys, indicating the existence of magnetic clusters in the Fe-rich samples.     

The quadrupole interaction of57Fe in Ti

The quadrupole interaction of⁵⁷Fe in titanium was studied by Mössbauer spectroscopy and by the time-differential perturted angular correlation technique, using an implanted and diffused source of⁵⁷Co in titanium. From the latter measurements a quadrupole interaction frequencyv _Q = 2.22 ± 0.42 MHz was derived. The modulation amplitude of the delayed coincidence spectrum combined with the Mössbauer spectra indicate a high degree of substitutionality of the cobalt in the titanium.     

The hyperfine magnetic field at57Fe and181Ta in Hf(Fe1−x Co x )2 system

The hyperfine magnetic field at⁵⁷Fe in the ferromagnetic Laves compounds Hf(Fe_1?x Co _x )₂ was measured by the Mössbauer effect method. The substitution of Fe atoms by Co atoms induces a gradual change ofB _hf(Fe) and a decrease in the magnetic moment values in Fe?Co sublattice. The perturbed angular correlation measurements of¹⁸¹Ta were carried out forX=0,X=0.1,X=0.55 at 300 K, andX=0.4 atT=400°C. An abrupt change ofB _hf (Ta) in 0<X<0.1 was observed.     

The temperature dependence of the57Fe hyperfine magnetic field distribution in Fe-Ni

The temperature dependence of the⁵⁷Fe hyperfine magnetic field (hmf) in Fe-Ni is stronger than the temperature dependence of the⁵⁷Fe hmf in pure Fe. By analyzing the shape of the⁵⁷Fe hmf distribution, and with the help of experiments with Si in Fe-Ni, we deduce that this anomalous temperature dependence originates from a large thermal sensitivity of the magnetic moments at those Fe atoms with more Ni nearest neighbors. A strong temperature dependence of the recoilfree fraction was also observed in Fe-Ni alloys. We suggest that a large mean square thermal displacement of Fe atoms in Fe-Ni is the cause of the anomalous temperature dependence.     

The splitting of hyperfine lines of57Fe nuclei in RF magnetic field

It is shown experimentally, that for Moessbauer nuclei affected by the radio-frequency (RF) magnetic field of sufficient intensity at frequencies corresponding to NMR, splitting of Zeeman sublevels of nuclei and changes in Moessbauer spectral structure occurs. Depending on the frequency of alternating field each spectral line is splitinto (2·Ig,e +1) comporients, Ig,e-being the nuclear spin of ground and excited state, respectively. The intensity of RF components and the energy gap between them are extremely sensitive to the frequency and the intensity of the RF magnetic field.     

ENDOR and transferred hyperfine interaction of impurity rare-earth ions with nearest diamagnetic ions in crystals

The tetragonal Er³⁺ ion associated with the interstitial F^? ion along the [100] axis in CaF₂ is studied using ENDOR. The parameters of the transferred hyperfine interaction and of the nuclear Zeeman interaction of the surrounding fluorine ions are determined. Anomalously large values of the pseudo-nuclear Zeeman effect on the F^? nuclei are found. The theoretical analysis of these parameters is carried out in a frame of operator techniques in the theory of transferred hyperfine interactions. A number of useful relations for practical calculations of the values of the local field at ligand nuclei are reported.