Third neighbour hyperfine field shift in a diluteNiAl alloy

In the binary Ni_98.5Al_1.5 alloy we observed well resolved satellite hyperfine fields at¹¹¹Cd nuclear probes. The hyperfine shifts derivated are −4.0(3); −8.5(3) and ⃛14.0(3)% relative to the pure nickel value. From the relative intensity of the four components as well as from the quadrupole interaction data we identify the satellites as impurity-probe configurations containing zero, one, two or three Al impurities in the third neighbour shell only. The third neighbour contribution to the hyperfine field at Cd in nickel equals ΔH ₃= +4.5kG/μ _B-atom, allowing an estimate ΔH ₁≃ −17.8 kG/μ _B-atom for the first shell contribution, confirmed by a similar experiment on Ni_98.5Pd_1.5.     

Magnetic hyperfine field of Ta in iron measured by means of the dpac method

The magnetic hyperfine field of Ta in iron was measured by means of DPAC using the 5/2⁺ state in¹⁸¹Ta. At room temperature, this field was found to be |H _hf(RT)|=6.08(7) T, which confirms the result of an earlier DPAC experiment. A hyperfine anomaly^5/2Δ^7/2=−4.6(23)% between the above state and the 7/2⁺ ground state of¹⁸¹Ta is deduced.     

Magnetic hyperfine field of arsenic in nickel by NMR/ON of71,72As

The magnetic hyperfine splitting frequencies of⁷¹AsNi and⁷²AsNi in a 0.11 Tesla external magnetic field have been determined by NMR/ON method as 66.00(6) MHz and 106.17(13) MHz respectively. Using the known magnetic moments of μ(⁷¹As)=1.6735(18) and μ(⁷²As)=−2.1566(3), the hyperfine fields were deduced asB _hf(⁷¹AsNi)=12.824(19) Tesla andB _hf(⁷²AsNi)=12.807(16) Tesla.     

Hyperfine magnetic field of Zn in iron

Precise hyperfine field value of zinc in iron has been determined by nuclear magnetic resonance on oriented nuclei (NMR/ON): B_hf (ZnFe)=−18.785 (35) T at 7 mK. The relaxation constant of Zn in iron is established C_K=14(3) Ks. The new hyperfine field value of zinc in iron allows a more precise reevaluation of the magnetic moments of^69mZn and^71mZn measured with NMR/ON. and the NICOLE Collaboration, CERN     

Transferred hyperfine field in the pseudo-binary compound Y(Fe,Mn)2

The NMR of⁸⁹Y in Y(Fe_1−xMn_x)₂ has been observed. Two kinds of Mn moments were estimated by analyzing the⁸⁹Y hyperfine field: (1) the low spin state with about 0.6 μ_B in antiparallel to Fe moment and (2) the high spin state with about 2.8 μ_B in parallel to Fe moment. The magnetizations estimated from NMR results are in good agreement with those of magnetization measurements.     

The magnetic hyperfine field of lutetium in iron by NMR/ON

Nuclear magnetic resonance of oriented¹⁷⁷Lu in iron has been found with a sample prepared by on-line implantation of¹⁷⁷Lu in iron at T<0.2 K. The broad resonance, FWHM=20.5 (1.3) MHz, has a centre frequency of _L=355.06 (51) MHz at zero external field. With the g-factor of¹⁷⁷Lu g=0.637 (3) from literature the magnetic hyperfine field of Lu in Fe is derived as B_hf=–73.12(36) T. Static nuclear orientation data are not compatible with a two site model where the nuclei which are oriented experience the hyperfine interaction found in NMR/ON. A fraction with a lower hyperfine field is necessary to explain the data.     

The hyperfine field of krypton in iron

The hyperfine field of krypton nuclei at lattice sites in iron has been determined using nuclear orientation. From the anisotropy of the electrons emitted in the decay of⁸⁵Kr implanted in iron, a hyperfine field value of +31.2(8) T was deduced for a substitutional fraction of approximately 37%. Also, a relaxation time of the order of 900 see was observed at temperatures between 7 and 11 mK.     

Negative muon spin precession in ferromagnetic iron and the hyperfine anomaly

The hyperfine field (B _μ ^hf ) at the negative muon μ⁻ in ferromagnetic iron was investigated by means of the zero-field μ⁻ spin precession technique. In the temperature range 320–690 K,B _μ ^hf for μ⁻ Fe departs from the magnetization curve of pure iron in the same way as the hyperfine field seen by a⁵⁵Mn impurity in dilute MnFe measured by NMR. The hyperfine anomaly for μ⁻ Fe relative to dilute (1.5 at.%)⁵⁵Mn in iron is found to be −0.9(3)% and temperature independent over the temperature range investigated.     

Concerning the shift of nonlinear optical resonances in a magnetic field

The shift of components of the magnetic hyperfine structure (MHS) of a vibrational-rotational molecular transition in a weak magnetic field is explored. The numerical data are given for the methane transition at λ=3.39 μm [theF ₂ ⁽²⁾ component of theP(7) line of thev ₃ band]. The shift of the line contour due to the magnetic field is found when the MHS components overlap.     

Magnetic hyperfine field of Se in nickel measured by means of the DPAC method

The magnetic hyperfine field of Se in nickel was measured by means of the time-differential perturbed angular correlation (DPAC) technique, using the 755–250 keV γ-ray cascade fed in the decay of⁷⁷Br. A value ofB _hf(NiSe)=+15.11(35) T was obtained at room temperature. The half-life of the 250 keV state and the anisotropy of the 755–250 keV cascade were found to beT _1/2=9.68(6) ns andA ₂₂=−0.454(9), respectively.     

Magnetic hyperfine field of Hg in nickel and the sign of magnetic moment of 197mAu by NMR-ON

Nuclear magnetic resonance on oriented nuclei (NMR-ON) measurements were performed on the successive decay of ^197mHg–^197mAu in Ni. The NMR-ON resonance spectra of ^197mHgNi were obtained by detecting the 134 keV γ-ray from the decay of ^197mHg and the 279 keV γ-ray from the decay of ^197mAu. The magnetic hyperfine splitting frequency of ^197mHgNi in an external magnetic field of 0.2 T has been determined as 16.55(6) MHz. With the known g-factor of ^197mHg the hyperfine field of B₈₂(^197mHgNi)= -13.53(6) T was deduced. The anisotropy of the 279 keV γ-ray (^197mAu to ¹⁹⁷Au) increased at the resonance. This phenomenon was explained using the spin inversion process including the lifetime of the isomer and the spin–lattice relaxation time. The sign of the g-factor of ^197mAu was determined to be positive. This revised version was published online in August 2006 with corrections to the Cover Date.     

Shapes of the neutron-rich 88-94Kr nuclei

Neutron-rich, ^88-94Kr nuclei, populated in spontaneous fission of ²⁴⁸Cm, have been studied with EUROGAM 2, by measuring prompt γ-rays. Many new excited states in even-even Kr isotopes have been identified. For the first time spins and parities were determined experimentally in these nuclei. Our results indicate that the quadrupole deformation of Kr isotopes will appear only above N = 58, as observed in Sr and Zr nuclei. The newly found 3^- level at 1506.4 keV in ⁹⁰Kr suggests the exsistence of a new region of increased octupole correlations, probably associated with the ν(d _5/2 h _11/2) pair of Δl = Δj = 3 orbitals. Received: 18 September 2000 / Accepted: 18 October 2000     

Hyperfine Interactions in CeT2Ge2 (T = Mn,Co) Heavy Fermions Compounds Measured by TDPAC

Time Differential Perturbed γ–γ Angular Correlation (TDPAC) technique was used to measure the magnetic hyperfine field at both Ge and Ce sites in CeMn₂Ge₂ and CeCo₂Ge₂ intermetallic compounds. The ¹¹¹In (¹¹¹Cd) probe nuclei was used to investigate the hyperfine interaction at Ge sites, while the ¹⁴⁰La (¹⁴⁰Ce) nuclei was used to measure the magnetic hyperfine field at Ce site. The present measurements cover the temperature ranges from 10–460 K for CeMn₂Ge₂ and 9–295 K for CeCo₂Ge₂, respectively. The result for ¹¹¹Cd probe showed two distinct electric quadrupole frequencies above magnetic transition temperatures, in both compounds and a combined interaction in the magnetic region. The temperature dependence of the magnetic hyperfine field at ¹¹¹Cd at Mn site for the CeMn₂Ge₂ compound showed a transition from ferromagnetic to antiferromagnetic phase around 320 K and from antiferromagnetic to paramagnetic phase at 420 K. While a small magnetic field was measured on ¹¹¹Cd at Co site, no magnetic field on ¹⁴⁰Ce site was observed in CeCo₂Ge₂. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine magnetic fields in Fe−Co alloys and their tempera ture dependences

We obtained⁵⁷Fe hyperfine field parameters from Fe₁−x-Co _x alloys (0≤x≤0.6) from 77 K to 900 K. We first discuss the origin of the low temperature hyperfine fields in terms of the 3d and 4s electrons at⁵⁷Fe atoms. The⁵⁷Fe hyperfine magnetic field (hmf) of Fe-Co alloys depends more weakly on temperature than the hmf of pure Fe. This temperature dependence occurs because the alignment of the magnetic moments at both the Fe atoms and at the Co atoms depend on temperature in the same way as the bulk magnetization of Fe-Co alloys.     

Study of the modifications of the electric field gradient in hexafluorohafnates of transition metals above room temperature

The temperature dependence above room temperature of the hyperfine quadrupole interactions measured by the time differential perturbed angular correlations technique at hafnium sites in AHfF₆·nH₂O, with A=Co and Zn andn=6, 4 and 0, is presented. The different steps of the dehydration process are reflected by modifications on the hyperfine quadrupole parameters at increasing temperature. The changes in the electric field gradient as water molecules are lost are interpreted in terms of distortions induced in the [HfF₆]²⁻ octahedrons.     

Magnetic Moment of the 3/2− Ground State of 185W

Nuclear magnetic resonance measurement have been performed for ¹⁸⁵W oriented at 8 mK in an Fe host. The magnetic hyperfine splitting frequency at an external magnetic field of 0.1 T was determined to be 196.6(2) MHz. With the known hyperfine field of B _hf = −71.4(18) T, the nuclear magnetic moment of ¹⁸⁵W is deduced as μ(¹⁸⁵W) = +0.543(14) μ_N.     

The electric field gradient of111Cd in an α-Al2O3 single crystal

Radioactive¹¹¹In⁺ ions were implanted into an α-Al₂O₃ single crystal. The hyperfine parameters of¹¹¹Cd at substitutional Al lattice sites were identified by measuring the perturbed angular correlation for different sample orientations. The electric field gradientV _zz =1.04(17)·10²²V/m² was obtained from the quadrupole coupling constant. This result is compared with the efg values of²⁷Al in α-alumina and¹¹¹Cd in α-Fe₂O₃, which also has the corundum structure. Two additional fractions with broad frequency distributions were observed, one of which is attributed to¹¹¹Cd atoms in a strongly distorted Al₂O₃-lattice.     

On the behaviour of Er3+ ion in tetragonal crystalline field

Crystal field parameters for ErGaG and Er³⁺ YAlG and used to compute the temperature dependence of Schottky specific heat, paramagnetic susceptibility, magnetic anisotropy,μ _eff and quadrupole splitting in the range 10–400 K. The hyperfine interaction parametersA andB for¹⁶⁶Er and¹⁶⁷Er in both the systems are also obtained and in turn used to estimate the nuclear specific heat contribution. The studied parameters compare well with the available experimental results.     

Influence of 50 MeV Lithium Ion Irradiation on Hyperfine Interactions of Cr0.5 Li0.5 Fe2O4

Spinel oxide Cr_0.5 Li_0.5 Fe₂O₄ has been irradiated at Nuclear Science Centre, New Delhi, by 50 MeV lithium ions of fluence 5*10¹³ ions/cm² and irradiation effect on hyperfine interactions has been investigated by Mossbauer spectroscopy. The Mossbauer spectrum of irradiated sample shows no paramagnetic doublet contribution and the hyperfine fields corresponding to the Fe³⁺ in the octahedral (B) and the tetrahedral (A) sites are very well separated. That is the observed superimposed A and B sites in unirradiated sample are split into separate lines after Li irradiation. Further an increase of the intensity of the lines (2)–(5) with respect to (1)–(6) signals an orientation of the hyperfine magnetic field towards a direction perpendicular to the ion path due to the irradiation induced strain by the latent tracks. The computer simulation of Mossbauer spectra indicated that the irradiated Fe³⁺-site occupancy of the A-site hyperfine field increased from 43% to 55% whereas the B-site hyperfine field decreased from 57% to 45% compared to unirradiated sample.     

The Nonanuclear [Mo(IV){(CN)Fe(III)(3-ethoxy-saldptn)}8]Cl4 Complex Compound Exhibits Multiple Spin Transitions Observed by Mössbauer Spectroscopy

The hyperfine interactions at ¹⁸¹Ta ions on Fe³⁺ sites in α-Fe₂O₃ (hematite) were studied in the temperature range 11–1100 K by means of the perturbed angular correlation (PAC) technique. The ¹⁸¹Hf(β⁻)¹⁸¹Ta probe nuclei were introduced chemically into the sample during the preparation. The hyperfine interaction measurements allow to observe the magnetic phase transition and to characterize the supertransferred hyperfine magnetic field B_hf and the electric field gradient (EFG) at the impurity sites. The angles between B_hf and the principal axes of the EFG were determined. The Morin transition was also observed. The results are compared with those of similar experiments carried out using ¹¹¹Cd probe. ^aAlso at Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Argentina.