Magnetic Hyperfine Splitting Research Articles

Range of magnetic order in Zr(Fe1-xCox)y(0⩽x⩽1, 1.8⩽y⩽2.1)

The bulk magnetic properties as well as the 57Fe hyperfine parameters of the pseudobinary compounds Zr(Fe1-xCox)2 were studied in the whole concentration range with the stoichiometry sometimes deviating from 2. A transition from ferromagnetism to paramagnetism is observed in this system at a certain critical concentration which sensitively depends on stoichiometry and on the sample preparation: in the concentration range 0.5<x<0.75 cluster-glass behavior as well as long-range magnetic ordering can be obtained. In a certain temperature concentration range in the presence of local moments was observed. In the region 0.5<x<0.77 the existence of non-magnetic Fe atoms in a magnetic matrix was found even at liquid helium temperatures. For concentrations x>or=0.77 not even short-range magnetic order (visible as magnetic hyperfine splitting in a Mossbauer spectrum could be detected at T=4.2K. The discrepancies in the results published by different authors could be due to the effect of heat treatment. The magnetic phase diagram proposed by Muraoka et al. (1979, 1980) is modified.

A Mössbauer study of the ferrimagnetic Fe1−xCrxBO3 system

Mössbauer effect measurements were made on solid solution Fe1−xCrxBO3, with 0⩽x⩽0.60, at room and at liquid nitrogen temperatures and on Fe0.50Cr0.50BO3 at temperatures from 82.5 to 150 K. The hyperfine field strength at Fe3+ sites decreases with increased Cr content. The isomer shift increases appreciably in samples containing Cr at low concentrations. The Mössbauer linewidth increases with increasing Cr content and exhibits a shoulder at 0.40⩽x⩽0.60. The data suggest that the presence of Cr3+ ions disrupts the magnetic superexchange interaction. Variations in the isomer shift, magnetic hyperfine splitting and linewidth as a function of increasing temperature in samples of Fe0.50Cr0.50BO3 suggest that a significant antiferromagnetic component is present in samples with Cr concentrations 0.40⩽x⩽0.60.

Nuclear magnetic resonance on oriented194Ir (T 1/2=19.4 h) in Fe and Ni

The hyperfine interaction of194Ir (j π =1−;T1/2=19.4 h) in Fe and Ni has been investigated with the technique of nuclear magnetic resonance on oriented nuclei. For both systems the electronic-orbital-momentum induced electric quadrupole splitting could be resolved. The magnetic and electric hyperfine splitting frequencies,v M =¦gμ N BHF/h¦ andv Q =e2qQ/h, respectively, were measured as:194IrFe:v m =408.54 (23) MHz;v q =−2.47(20) MHz;194IrNi:v M =135.24(5) MHz;v q =−1.23 (3) MHz. Taking into account a 3% uncertainty arising from hyperfine anomalies theg-factor is deduced as ¦g¦=0.39 (1). The electric quadrupole moment,Q=+0.352 (18)b, is slightly smaller than expected from the known systematics of deformation parameters in this mass region.

In situ Mössbauer spectroscopic study of iron III chloride intercalated in graphite under reaction conditions

In situ 57Mössbauer spectroscopy has been used to study the process of reduction and Fischer-Tropsch reactions on FeCl 3 intercalated in graphite layers. It is found that on flowing H 2 on graphite intercalated by FeCl 3 at 400° C, FeCl 3 converts to FeCl 2 and partly to small particles of α-Fe. The Mössbauer spectra of the reduced sample are superposition of a sextuplet and two quadrupole doublets indicative of metallic iron and two species of FeCl 2. However, at room temperature and at 400° C for a short period of reduction the magnetic hyperfine splittings ( ca. 295 kOe and 262 kOe respectively) are smaller than the corresponding parameters for bulk metallic iron. The differences have been attributed to the interaction between the monolayers of iron atoms and the carbon nets of the graphite support. When the reduction was carried out for a longer period, α-Fe was formed. When a sample reduced for a short period of time is heated at 400°C in the presence of the synthesis gas, part of the iron particles sinter, and α-iron is observed. On heating the above sample once again at 400°C in the presence of the synthesis gas, the remaining small particles of iron are totally converted to the bulk phase (α-Fe). Experimental observations indicate that α-Fe and FeCl 2 are present on the surface as well as inbetween the intercalated graphite layers.

Nuclear orientation study of97, 103, 105Ru in Fe

Angular distributions have been measured forγ-rays emitted following the decays of97, 103, 105Ru oriented in an iron matrix at temperatures down to 2.8mK. From the temperature dependence of theγ-anisotropies the magnetic hyperfine splitting frequenciesν M =|gμ N B HF/h| of97, 103, 105RuFe were found to be 110(7), 57(15) and 80 −50 +17 MHz, respectively. With the known hyperfine fieldB HF=−489.6(4.0) kG the nuclearg-factors are derived as ∣g(97Ru;j π=5/2+)∣=0.29(2), ∣g(103Ru;j π=3/2+)∣=0.15(4) and ∣g(105Ru;j π=3/2+)∣=0.21 -0.13 +0.05 . The analysis for103RuFe has been performed with the assumption ofj π=3/2+ and 5/2+ for the ground state of103Ru. Taking into account experimentally knowng-factors of 3/2+ and 5/2+ states in this mass region, our data strongly favour the assignmentj π=3/2+ for the103Ru ground state.

Nuclear magnetic resonance on oriented109In(4.2h) and110In(4.9h) after recoil implantation into Fe

Radioactive109In(jπ=9/2+;T1/2=4.2h) and110In(jπ=7+;T1/2=4.9h) were produced via the109Ag (α, xn) reactions and recoil-implanted into Fe foils. With the technique of nuclear magnetic resonance on oriented nuclei the magnetic hyperfine splittings were investigated in external magnetic fieldsB0=0.5...4.2 kG. The zero-field splitting were measured as 268.9(2)MHz and 147.3(3)MHz for109InFe and110InFe, respectively. With the known hyperfine fieldBHF(InFe)=−286.6(5) kG the nuclearg-factors are deduced asg(109In)=1.231(3) andg(110In)=0.674(2). Our result for109In shows that theπg9/2g-factors vary by only ∼0.1% betweenA=109 and 115. For the |π9/2vd5/2〉7+ of110In the additivity relation of magnetic moments is fulfilled to on accuracy of 0.3(3)%.

Nuclear magnetic moment of 2.8 dIn111

The hyperfine interaction of /sup 111/In(j/sup ..pi../ = 9/2/sup +/, T/sub 1/2/ = 2.8 d) in Fe has been investigated with nuclear magnetic resonance on oriented nuclei at temperatures of approx.0.01 K. The magnetic hyperfine splitting ..nu../sub M/ = Vertical Barg..mu../sub N/B/sub HF//hVertical Bar and the resonance shift with an external magnetic field were measured as 267.2(2) MHz and -0.906(18) MHz/kG, respectively. With the known hyperfine field B/sub HF/ = -286.6(5) kG the nuclear magnetic moment is deduced to be u = (+) 5.504(10) ..mu../sub N/. The differential resonance displacements of the 171- and 245-keV nuclear magnetic resonance on oriented nuclei resonances measured at THETA = 0/sup 0/ and 90/sup 0/ were found to be nu-bar(0/sup 0/,171)-nu-bar(0/sup 0/,245) = -3(13) kHz and nu-bar(0/sup 0/,245)-nu-bar(90/sup 0/,245) = +3(30) kHz. Taking into account these data the quadrupole splitting ..nu../sub Q/ = e/sup 2/qQ/h of /sup 111/InFe is estimated to be -0.3(1.1) MHz.

GFactors of 14.6 h 90Nb and 10.2 d 92mNb

Abstract The magnetic hyperfine splitting frequencies νM = gμNBHF/h of 14.6 h 90Nb (jπ = 8+) and 10.2 d 92mNb (jπ = 2+) as dilute impurities in Fe have been measured with NMR on oriented nuclei as 125.05(1) MHz and 618.8(1) MHz, respectively. With the known hyperfine field B HF ( Nb Fe ) = − 264.54(19) kG the g-factors are deduced as g( 90 Nb ) = 0.6201(4) and g( 92m Nb) = 3.068(2) . The additivity relation of magnetic moments is tested for the ( π g 9 2 ν g −1 9 2 ) multiplet in 90Nb, and the nuclear g-factors are discussed in the frame of known magnetic properties in the mass region A ∼ 90.

G-Factors of 20 h 181Re, 64 h 182Re and 38 d 184Re

The magnetic hyperfine splitting frequencies ν M = gμ N B HF h of 181 Re(j π = 5 2 +; T 1 2 = 20 h), 182 Re (j π = 7 +; T 1 2 = 64 h) and 184 Re (j π = 3 − ; T 1 2 = 38 d) as dilute impurities in Fe have been determined with NMR on oriented nuclei as 729.3(3) MHz, 231.3(1) MHz and 482.5(1) MHz, respectively. Neglecting hyperfine anomalies, which are expected to be small, the known hyperfine field B HF (ReFe) = −750(15) kG can be used to derive the g-factors as g( 181 Re) = 1.276(26) , g( 182 Re) = 0.405(8) and g( 184 Re) = 0.844(17) . The g-factors are discussed in the framework of the Nilsson model.

M�ssbauer study of narrowing of the magnetic hyperfine splitting spectra of permalloy and invar due to the radio freouency field

M�ssbauer study of narrowing of the magnetic hyperfine splitting spectra of permalloy and invar due to the radio freouency field

On the magnetic dipole moment of the153Tb ground state

Temperature dependence of the angular distribution anisotropy of the 212·0 keV gamma-ray following the decay of153Tb oriented in a gadolinium host was measured at temperatures from 16 to 70 mK. Magnetic dipole hyperfine splitting parameter a0 for153Tb(Gd) and magnetic dipole moment of the153Tb ground state were estimated to be ¦a0¦≧1·2×10−5 eV and ¦μ¦≧≧3·1 nuclear magnetons, respectively.

Nuclear magnetic moment of 6.9 hMom93

With the technique of nuclear magnetic resonance on oriented nuclei, the magnetic hyperfine splitting of $^{93}\mathrm{Mo}^{m}\mathrm{Fe}$ has been investigated in external magnetic fields ${B}_{0}=1\dots{}7$ kG at temperature of \ensuremath{\sim}0.01 K. The zero-field splitting and the resonance shift with ${B}_{0}$ were measured $|\frac{g{\ensuremath{\mu}}_{N}{B}_{\mathrm{HF}}}{h}|=183.84(1)$ MHz and $|\frac{g{\ensuremath{\mu}}_{N}}{h}|=0.721(8)$ MHz/kG, yielding consistent values for the nuclear $g$ factor of 0.947(19) and 0.946(9), respectively. From the mean value $|g|=0.946(8)$ the magnetic moment is derived as $|\ensuremath{\mu}|=9.93(8){\ensuremath{\mu}}_{N}$. This confirms the structure of the ${21/2}^{+}$ state as ${|{(\ensuremath{\pi}{g}_{{\frac{9}{2}}^{+}})}_{{{8}^{+}}^{2}}\ensuremath{\nu}{d}_{{\frac{5}{2}}^{+}}〉}_{{\frac{21}{2}}^{+}}$ for which $\ensuremath{\mu}=10.00(5){\ensuremath{\mu}}_{N}$ is expected taking into account experimentally known magnetic properties of neighboring nuclei. Our measurements show that the additivity relation for the magnetic moments holds well for this state, and that the results of a previous nuclear magnetic resonance on oriented nuclei measurement must be erroneous.RADIOACTIVITY $^{93}\mathrm{Mo}^{m}$ [from $^{93}\mathrm{Nb}(\ensuremath{\alpha},3np)$]; measured ${I}_{\ensuremath{\gamma}}$ ($\ensuremath{\theta},T,\ensuremath{\nu}$) of oriented states; NMR on oriented nuclei. Deduced $g$, $\ensuremath{\mu}$, relaxation times.

Mössbauer study of narrowing of the magnetic hyperfine splitting spectra of invar due to the radio frequency field

Experimental results are presented which suggest that the heating of a sample plays a primary role in the previously observed narrowing of the magnetic hyperfine spectrum of invar in a radio frequency field. Simultaneous storing of the spectrum both during the application and in the absence of r.f. field was applied. The dependence of the spectrum narrowing on the r.f. field duration time to the dwell time ratio at constant r.f. intensity is found to be similar to that on the r.f. field intensity previously observed. Some other arguments are also presented suggesting that for invar the assignment of the spectrum narrowing to thermal effects is better confirmed than that to the r.f. collapse effect.

A 57Fe Mossbauer spectroscopic study of a selection of Australian and other goethites

The 57Fe Mossbauer spectra recorded at room temperature for seven Australian and two U.S.A. goethite mineral specimens of various composition and extent of aluminium substitution, particle size and origin are presented. Eight of these exhibit six-line magnetic hyperfine spectra with differing hyperfine magnetic splitting and asymmetric line broadening, resulting from super-paramagnetic relaxation effects. The results show that the relation between the decreasing magnitude of the hyperfine magnetic splitting with both increasing aluminium content and decreasing particle size, as previously reported for aluminium-substituted goethites, does not hold generally for the natural goethites studied here. For these, such a relation is more complex and appears to depend, not only on the extent of aluminium substitution, but also on the other impurity substituents in the goethite specimens. These combined effects make it difficult to use the magnitude of H to measure the particle size or to relate the type of Mossbauer spectrum with the mode of occurrence of the goethite.

99Ru Mössbauer spectra of quaternary ruthenium(V) oxides with the hexagonal barium titanate structure

99Ru Mössbauer spectra have been recorded at 4.2 K for the quaternary oxides Ba 3Ru 2 MO 9 ( M = Mg, Ca, Sr; Co, Ni, Cu, Zn; and Cd), all of which crystallize with the hexagonal barium titanate structure. The Ca, Sr, and Cd compounds give sharp symmetrical singlets with chemical isomer shifts typical of ruthenium in the +5 oxidation state. The absence of magnetic hyperfine splitting is consistent with the published interpretation of magnetic susceptibility data in terms of binuclear intracluster spin pairing which leads to an S = 0 ground state. In contrast, magnetic hyperfine splitting is seen for the Mg, Zn, Co, Ni, and Cu compounds; this can be interpreted only in terms of long-range magnetic order and the absence of such an S = 0 ground state at 4.2 K. This differs from the published interpretation of the magnetic susceptibility data for Ba 3Ru 2MgO 9 in the low-temperature region. The magnetic flux densities at the ruthenium nuclei in the magnetically ordered compounds (32.5–51.6 T) are lower than those normally associated with ruthenium(V), and the spectra cannot be curve fitted satisfactorily with single hyperfine patterns having the natural linewidth. Possible reasons for these observations are discussed.

Iron pentacarbonyl decomposition over Grafoil. Production of small metallic iron particles

Mossbauer spectroscopy was the principal technique used to study the adsorption and thermal decomposition of iron pentacarbonyl on a high surface area, oriented graphite (Grafoil). The iron carbonyl physisorbs on the graphite at temperatures less than ca. 300 K, whereas decomposition of the carbonyl occurs upon heating to 378 K. The Mossbauer spectra of the decomposition product are sextuplets indicative of metallic iron. However, the room-temperature magnetic hyperfine splitting (ca. 300 kOe) is smaller and the peak widths (ca. 1.5 mm s-/sup 1/) are larger than those corresponding spectral parameters for bulk metallic iron (330 kOe and 0.28 mm s-/sup 1/, respectively). Computer simulations suggest that these differences are due to magnetic relaxation and to a distribution of magnetic hyperfine fields. For consistency with the Mossbauer spectra, it is proposed that the iron particles are present as thin rafts on the graphite surface. Transmission electron microscopy shows that these rafts are preferentially located along edges and steps on the graphite. Heating to 450 K leads to significant sintering of the iron particles.

Ground-state nucleargfactor ofRu97

The magnetic hyperfine splitting constant $\frac{g{\ensuremath{\mu}}_{N}{H}_{\mathrm{HF}}}{h}$ of $^{97}\mathrm{Ru}$ as a dilute impurity in Fe has been determined by the technique of nuclear magnetic resonance on oriented nuclei to be 117.69\ifmmode\pm\else\textpm\fi{}0.02 MHz. With the known hyperfine field for $\mathrm{Ru}\mathrm{Fe}$ of -504\ifmmode\pm\else\textpm\fi{}12 kG the ground-state nuclear $g$ factor of $^{97}\mathrm{Ru}$ is deduced to be (-)0.306\ifmmode\pm\else\textpm\fi{}0.008. The resonance shift and the spin-lattice-relaxation time have been measured as functions of an external magnetic field.RADIOACTIVITY $^{97}\mathrm{Ru}$ from $^{96}\mathrm{Ru}$($n$,$\ensuremath{\gamma}$); NMR on oriented nuclei. Deduced $\ensuremath{\mu}$, Knight shift, relaxation times.

Mössbauer spectroscopy of Escherichia coli and its iron-storage protein

57Fe Mössbauer spectra of whole frozen Escherichia coli cells and of an iron storage protein isolated from iron-rich cells of E. coli have been measured over a range of temperatures down to 0.08 K. The spectra of E. coli cells with high iron content and of the iron storage protein were found to be very similar. Above 4 K these spectra consist of a quadrupole split doublet characteristic of Fe 3+ . Below 3.5 K, the spectra display magnetic hyperfine splitting which is temperature dependent, and point to the existence of an ordered magnetic phase associated with a saturation magnetic hyperfine field of 43 tesla in both samples. The results indicate that the bulk of iron in the iron-rich cells is in the form of aggregates similar in nature to the iron cores in the isolated protein, although the latter account for not more than 1% of the total iron in the cells. The Mössbauer spectra of the isolated protein are different from those observed in ferritin, the iron-storage protein of plants and higher animals, showing that the iron cores in these two proteins are different.

A novel case of magnetic relaxation in the 99Ru Mössbauer spectrum of Na 3RuO 4

The magnetic properties of Na 3RuO 4 have been studied using 99Ru Mössbauer spectroscopy. Magnetic hyperfine splitting is seen at temperatures below 30°K. The value of the flux density at 4.2°K (58.58 T) is compatible with a saturation field at an S = 3 2 Ru V ion, and at intermediate temperatures approximately follows an S = 3 2 Brillouin function. The published interpretation of magnetic susceptibility data in terms of tetranuclear intracluster antiferromagnetism is shown to be incorrect, and it is concluded that Na 3RuO 4 shows antiferromagnetic three-dimensional long-range order with a Néel temperature of T N = 30 ± 1°K. Between 25 and 30°K motional narrowing of the spectrum is seen, which is probably due to a slow spin-spin relaxation within the crystal-field levels of the 4 A 2 g ground state of the Ru V ion. This is the first observation of relaxation effects in a 99Ru spectrum.

Interferometric determination of the magnetic hyperfine splitting factors for some excited configurations of Bi I

The first interferometric study of the resonance lines around 200 nm of Bi I has been performed. The hyperfine splitting constants of the levels 6p26d2D3/2, 6p26d2D5/2, 6p27s4P3/2, 6p27s4P5/2, 6p27d2D3/2, 6p27d2D5/2 and 6p28s4P1/2 have been determined. No evidence of B values different from zero was found with the exception of the 6p27s4P5/2 level.