Magnetic properties of (ErxY1−x)Al2: Magnetic measurements and neutron diffractions data

The ac susceptibility, the low field magnetization and neutron diffraction experiment have been performed for concentrations 0.1<x<1. For x<0.4 the typical spinglass properties have been observed: cusp in the susceptibility, the cusp is affected by small static magnetic fields of a few hundred Gauss. The thermal remanent magnetization has also been detected. However properties are also present for the high concentration x=0.6 or 0.8. Neutron diffraction experiments at the D1B of the ILL show that there exists $\text{no}$ sharp change from long range order to the spinglass regime. For higher x values approximately 80% of the Er ions form long range order whereas for x<40% most of the ions are in the frozen paramagnetic state. The magnetic phase diagram for the whole concentration range is discussed.     

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.     

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.     

Mössbauer studies of mixed and substituted garnets

We report here our⁵⁷Fe Mössbauer studies on the mixed and substituted iron garnets. Magnetisation studies on substituted SmIG system {Sm_3?x Ca_x} [Sn_x Fe_2?x](Fe₃)0₁₂ (0.2≤x≤1.8) show that the T_c decreases as x increases. We attribute this to the reduced strength of a-d interaction as a result of dilution of a-site. While the Mössbauer spectra seem to reflect this, an interesting feature is the unresolved hyperfine spectrum seen at 80K for x=1.0, even though the transition temperature (T_c) is 285K. For this concentration, varying the rare earth ion from Sm to Er, results in very similar spectra. We speculate spin glass behaviour for x=1.0. In mixed and substituted garnet system {Gd_2.5R_0.2Ca_0.3} [Sn_0.3Fe_1.7](Fe₃)0₁₂ (R=Y, Sm, Eu, Ho and Er), we observe well resolved spectra with no change in the hyperfine field with substitution of rare earth. This is consistant with the dominance of a-d interaction in these systems.     

(Nd1-xErx)3Fe273Ti17化合物的结构与磁性

通过x射线衍射分析和磁性测量对(Nd1-xErx)3Fe273Ti17化合物的结构与磁性进行了研究.单相(Nd1-xErx)3Fe273Ti17化合物的成相范围为x=00—05之间，所有化合物均属于单斜晶系、Nd3(Fe,Ti)29型结构和A2/m空间群.着Er含量的增加，(Nd1-xErx)3Fe273Ti17化合物的晶胞体积、居里温度TC和5K下的饱和磁化强度Ms均单调减小，而5K下的饱和磁化强度Ms和Er含量的关系与稀释模型所描述的结果相一致.(Nd1-xErx)3Fe273Ti1 关键词： (Nd1-xErx)3Fe273Ti17化合物 磁晶各向异性 自旋重取向 磁相图     

掺铒铋酸盐玻璃的光谱性质和热稳定性研究

测试了铋酸盐玻璃(85-x)Bi2O3-(10+x)B2O３-5Na2O(x=0，5，10，15，20，25 mol%)中Er3+离子的吸收光谱、荧光光谱、荧光寿命及热稳定性.应用Judd-Ofelt理论计算了铋酸盐玻璃中Er3+离子的强度参数(Ω2=(352—386)×10-20cm2,Ω4=(138—152)×10-20cm2,Ω6=(093—117)×10-20cm2),应用McCumber理论计算了Er3+离子的受激发射截面(σe=(70—95)×10-21cm2)及Er3+离子4I13/2→4I15/2发射谱的荧光半高宽(FWHM=57—79nm)，测得了Er3+离子４I13/2能级荧光寿命(τm=265—159ms)，分析了玻璃的热稳定性能.研究了Er3+离子各种光谱参数对成分的依赖性，发现随着玻璃中B2O3含量的增加，强度参数Ωt(t=2,4,6)、荧光半高宽(FWHM)、热稳定性均相应增加，而测得的荧光寿命却减小.比较了不同基质玻璃中Er3+离子的光谱特性，结果表明掺铒铋酸盐玻璃更适合于掺Er3+光纤放大器实现宽带和高增益放大. 关键词： 铋酸盐玻璃 光谱性质 成分依赖性 Er3+离子     

Magnetic order observed in Er6Mn23H21 using the Mössbauer effect

The ferrimagnetic compound Er₆Mn₂₃ and its hydride Er₆Mn₂₃H₂₁ have been investigated using the ¹⁶⁶Er and ⁵⁷Fe (as dilute impurity) Mössbauer resonances. For the hydride a small ⁵⁷Fe magnetic hyperfine field is observed below 85 K indicating magnetic ordering. This observation is contrary to the previous assumption that the Mn sublattice must be non-magnetic. The ¹⁶⁶Er results demonstrate that the Er³⁺ magnetic moment is not “quenched” by crystal electric fields on hydrogenation.     

Fe Ion-induced phase transformation in 17/7 stainless steel

CEMS observation has showed the large difference in the fraction of the induced alpha phase between⁵⁶Fe ion and⁵⁷ion irradiation. In case of⁵⁷Fe ion irradiation, the projectile⁵⁷Fe probe atom observes the phase transformation which may be induced by itself. It is most probable that CEMS in⁵⁷Fe ion irradiation reflects the phase transformation due to compositional changes and alloying effects.     

Mössbauer studies at Milli-Kelvin temperature region

Using a³He dilution refrigerator, Mössbauer measurements at extremely low temperatures have been carried out. From the nuclear polarization of⁵⁷Fe in an Fe metal foil absorber, the lowest temperature was determined to be 5mK.⁵⁷Fe results on a triangular Fe³⁺cluster complex and¹¹⁹Sn results on RPd₂Sn(R=Er, Tm) are briefly presented.     

57Fe and 166Er Mössbauer and magnetic studies of RFe4B (R = Er,Tm, Lu) compounds

Magnetic and Mössbauer studies have been carried out on a series of ternary borides RFe₄B (R = Er, Tm, Lu) which have the hexagonal CeCo₄B type structure. These compounds are found to be magnetically ordered at room temperature. Magnetization studies in the temperature range from 5 to 300 K reveal the presence of compensation temperatures in Er and Tm compounds and indicate antiferromagnetic coupling between the rare earth and Fe moments. Room temperature ⁵⁷Fe Mössbauer studies yield values of hyperfine fields at the two Fe sites as 246 and 185 kOe in ErFe₄B and TmFe₄B, and 204 and 145 kOe in LuFe₄B. The ¹⁶⁶Er Mössbauer studies give nearly free-ion hyperfine field at the Er sites which indicates that the exchange interaction in ErFe₄B is much stronger than crystal field interaction.     

NMR study of local magnetic properties of beryllium substituted copper ferrite

The spin echo NMR spectra of⁵⁷Fe have been taken at 77 K to describe the local magnetic properties of beryllum substituted copper ferrite Cu_1−xBe_xFe₂O₄ for 0≤x≤0.2. From the spectra the concentration dependence of hyperfine magnetic fields for tetrahedral and octahedral sites have been derived. The results show that statistical distribution of beryllium atoms over magnetic sublattices takes place and suggest that only below x=0.2 solid solutions of beryllium copper ferrites can exist.     

Synthesis and conductivities of the apatite-type systems, La9.33+xSi6−yMyO26+z (M=Co, Fe, Mn) and La8Mn2Si6O26

Apatite-type oxides of formula (La/Sr)_10−xSi₆O_26+y have been attracting significant interest recently, because of their high oxide ion conductivity. In this paper we report the synthesis and conductivities of phases based on doping La_9.33Si₆O₂₆ with Co, Fe, Mn on the Si site, according to the formula La_9.33+x/3Si_6−xM_xO₂₆ (M=Co, Fe, Mn). Substitution limits observed were x≤1.5 (Co), x≤1.25 (Fe), x≤0.5 (Mn). Higher Mn levels could be achieved by substituting onto the La site, with it being possible to prepare the phase La₈Mn₂Si₆O₂₆. The highest conductivities were observed for the Co doped samples, although investigations into the dependence of conductivity on p(O₂) (0.2–10⁻⁵ atm.) indicated that the conductivity was dominated by the electronic component in these cases. In contrast, the conductivities for the Fe and Mn doped samples were mainly ionic in the same p(O₂) range. Experiments into varying the oxygen content of these doped phases indicated that increasing the oxygen content above the nominally stoichiometric O₂₆ appears to increase the oxide ion conductivity. Preliminary studies of the reactivity of the electrolyte La_9.33Si₆O₂₆ with potential SOFC cathode materials (La_1−xSr_xMO₃; M=Co, Fe, Mn) suggests that reaction can occur at high temperatures leading to the incorporation of the transition metal into the apatite electrolyte. However, the fact that these doped phases exhibit high conductivities suggests that this may limit any problems caused by such a reaction at the electrolyte-electrode interface. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Magnetic anisotropy in Fe/rare‐earth multilayers

Magnetic anisotropy of Fe/RE multilayers (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) was studied using ⁵⁷Fe Mössbauer spectroscopy. Perpendicular magnetic anisotropy was observed in Fe/Pr, Fe/Nd, Fe/Tb, and Fe/Dy multilayers. The external field dependence of the direction of magnetic moments was also examined for Fe/Tb multilayers. The results imply that the perpendicular magnetic anisotropy originates from the single ionic anisotropy of RE at the interfaces.     

Mössbauer spectroscopy in highT c superconductors

Mossbauer spectroscopy has recently been applied to study the new high T_c superconducting compounds RBa₂Cu₃O_z, using isotopes of rare earths mainly¹⁵⁵Gd and¹⁵¹Eu, and⁵⁷Fe, with different amounts of Fe ions replacing Cu. It was shown that magnetic moments on the rare earth site do not interfere with superconductivity. Fe at low concentrations (<1%) was found to replace Cu mainly in the Cu(1) site, and the Mossbauer spectra reveal different quadrupole doublets-fol lowing the different oxygen coordination around the Fe ion. The change of the relative intensities of the different doublets with z can easily be followed. For higher iron concentrations, it seems that increasing amounts of iron replace Cu in the Cu(2) site. For z<6.5, the iron reflects the magnetic ordering of Cu in this site, and the ordering temperature as function of z can be obtained. The agreement between neutron diffraction and Mossbauer measurements prove that Fe is a good probe for the magnetic behaviour of the Cu(2) ions. At low temperatures, Fe Mossbauer spectra of Fe in the Cu(1) site are also magnetically broadened, for all z. Superconducting-magnetic phase diagrams are also obtained in Y_1−x Pr_x Ba₂ Cu₃O_z as function of x and z. For z=7.1, T_N changes sharply with x. T_N=300, 230 and 35 K for x=0.8, 0.6 and 0.4 respectively, whereas for z=6.1 T_N changes very little with x. Mossbauer measurements performed on 5 at %⁵⁷Fe doped in CalaBaCu₃O_z show that most of the la occupy the Ba site. For z=7 about half the iron in the Cu(2) sites are magnetically ordered, with H_eff=520 kOe and T_N=400 K, even though the sample is superconducting with T_c=35 K. The possibility of coexistence between superconductivity and magnetic order in these systems will be discussed.     

57Fe NMR in Y3Fe4.5Ga0.5O12 single crystal

The angular dependence of the⁵⁷Fe NMR spectra in a single crystal of Ga substituted YIG is studied with special attention paid to the satellite lines of the octahedral iron. These satellites correspond to ferric ions in the neighbourhood of which the Ga³⁺ ion is located. The anisotropy of the hyperfine field of these satellites is in accord with the prediction of the independent bond model. A simple analysis indicates that the main source of the anisotropy, besides the dipolar interaction, is the change of the supertransferred part of the hyperfine field.Dedicated to Dr. Svatopluk Krupika on the occasion of his 65th birthday.     

Probe Mössbauer Diagnostics of Charge Ordering in Manganites CaCuxMn7–xO12 (0 ≤ x ≤ 1)

Journal of Experimental and Theoretical Physics - We present the results of our 57Fe probe Mössbauer study in manganites CaCuxMn6.96–x57Fe0.04O12 (0 ≤ x ≤ 1). We have...     

Structural and magnetic properties of nano-crystalline RuFe alloys prepared by organometallic synthesis

Nanoparticles of Ru_1-xFe_x (0≤x≤1) in a carbon matrix were synthesized over the entire composition range using organometallic precursors. For Fe concentrations with x<0.70, a hexagonal close-packed phase was formed whereas a body-centered cubic phase was observed for x>0.70. The crystallite sizes varied between 5–10 nm. In addition, multi-wall carbon nanotubes formed during the pyrolysis of the precursors. Increasing superparamagnetic order was observed with increasing Fe content.     

Site-selective detection of vibrational modes of an iron atom in a trinuclear complex

Nuclear inelastic scattering (NIS) experiments on the trinuclear complex [⁵⁷Fe{L-N₄(CH₂Fc)₂} (CH₃CN)₂](ClO₄)₂ have been performed. The octahedral iron ion in the complex was labelled with ⁵⁷Fe and thereby exclusively the vibrational modes of this iron ion have been detected with NIS. The analysis of nuclear forward scattering (NFS) data yields a ferrous low-spin state for the ⁵⁷Fe labelled iron ion. The simulation of the partial density of states (pDOS) for the octahedral low-spin iron(II) ion of the complex by density functional theory (DFT) calculations is in excellent agreement with the experimental pDOS of the complex determined from the NIS data obtained at 80 K. Thereby it was possible to assign almost each of the experimentally observed NIS bands to the corresponding molecular vibrational modes.     

Mössbauer spectra and magnetic properties of Sm2 (Co,Fe)17 alloys

Hyperfine Interactions - Sm2(Co1?x Fe x )17 alloys form the basis of a new class of permanent magnets. We have investigated these materials with57Fe Mössbauer spectroscopy. Alloys...     

Sperimagnetism in Fe78Er5B17 and Fe64Er19B17 metallic glasses: II. Collinear components and ferrimagnetic compensation

Magnetization measurements on an Fe(64)Er(19)B(17) glass and polarized-beam neutron scattering measurements on Fe(78)Er(5)B(17) and Fe(64)Er(19)B(17) were described in part I. The finite spin-flip neutron scattering cross sections were calculated using a sperimagnetic structure based on random cone arrangements of the magnetic moments. The temperature variation of the cross sections of Fe(64)Er(19)B(17) suggested that a compensated sperimagnetic phase existed at T(comp).The analysis of the non-spin-flip neutron scattering cross sections is described here in part II. Two spin-dependent total structure factors S(±±)(Q) were defined from these cross sections and, despite the limited range of the data 0.5 ?(-1) < Q < 6.5 ?(-1), their Fourier transform gave reliable spin-dependent radial distribution functions RDF(±±)(r). These were interpreted in terms of the atomic pair correlation functions ρ(±±)(AB)(r) and their weighting factors ω(±±)(AB). The data on Fe(64)Er(19)B(17) at 1.5 K showed, for example, how the directions of the magnetic sublattices can be defined uniquely. The analysis of the RDF(±±)(r) for Fe(64)Er(19)B(17) at 112 K confirmed that the mean collinear components of the magnetic moments , are zero on both sublattices in the compensated sperimagnetic structure at T(comp). The pre-peak in the spin-dependent total structure factors at 112 K showed that it originated in the atomic structure and it may involve Fe-Er-Fe 'collineations' at a radial distance of ≈6.0 ?. Finally, the RDF(±±)(r) of Fe(64)Er(19)B(17) at 180 K and of Fe(78)Er(5)B(17) at 2 K show that both glasses have the (μ(Fe) UP:μ(Er) DOWN) structure like the (Fe,Tb)(83)B(17) collinear ferrimagnets.