The Formation of Lithiated Ti-Doped α-Fe2O3 Nanocrystalline Particles by Mechanical Milling of Ti-Doped Lithium Spinel Ferrite

Perturbed Angular Correlation method has been used to study the hyperfine magnetic field in the Heusler alloy Pd₂MnSb(Sn). Ion implantation of the recoil ¹¹¹In nuclei following heavy ion nuclear reactions ¹⁰⁸Pd(⁷Li, 4n)¹¹¹In and ¹⁰⁸Pd(⁶Li, 3n)¹¹¹In has been used to great advantage in the present case resulting in large implantation efficiency. Only a few hours of irradiation time with moderate beam current of the order of 400–500 nA resulted in sufficient implanted ¹¹¹In activity on the sample for good quality measurements. The hyperfine field was measured at ¹¹¹Cd probe nuclei substituting Mn and Sb(Sn) sites as a function of temperature. The fraction of ¹¹¹Cd nuclei occupying Mn atom sites was found to increases with the annealing of sample at higher temperatures.     

Chemical order and magnetic properties of the Ni2−xMnSb system

The results of extensive magnetisation, X-ray and neutron powder diffraction measurements on the intermetallic compound series Ni_2-xMnSb, for 0?x?1, are reported. For x ?0.4, a high degree in the C1_b structure is observed, but for x?0.3, some disorder is evident. The series is ferromagnetic, with Curie temperatures rising from 368 to 732 K with decreasing nickel concentration. The magnetic moments all lie in the range (4.0±0.3)μ_B, with a maximum at a composition near x=0.45. The magnetic moments are largely associated with the ordered manganese sites, but it is possible that a small negative moment ?0.25μ_B may be associated with the “nickel sites” for x?0.3. This latter moment may be accounted for by disordered Mn atoms antiferromagnetically aligned.     

Hyperfine fields of 5sp shell impurities substituting Sb in the Heusler alloys Pd2MnSb and PdMnSb

Measurements of the hyperfine magnetic fields B_hf of Te and I impurities substituting Sb in the Heusler alloys Pd₂MnSb and PdMnSb clearly establish that the curve of B_hf versus impurity atomic number is shifted to the right by about 1 unit of atomic number for PdMnSb relative to Pd₂MnSb. This phenomenon, and the general shape of the curve can be understood in terms of the conduction electron polarization model developed by Blandin and Campbell.     

Spin polarization for electrons tunneling from MnxSb1−x

The spin polarization of electrons tunneling from Mn_xSb_1?x was measured over the full Mn concentration range 0 ? x ? 1. The polarization is positive and qualitatively similar to the magnetization per Mn atom of bulk material; for MnSb (x = 0.5) it is + 25%.     

The range of transferred hyperfine interactions in EuS

We report on a Mössbauer study of the transferred hyperfine fields at the ¹⁵¹Eu nuclei in the Eu_1?xSr_x series of mixed compounds. The totally transferred hyperfine field amount ?(5.3 ± 0.3) T corresponding to saturation values for the hyperfine field of ?(33.4 ± 0.2) T for x = 0 and ?(28.1 ± 0.2) T extrapolated for x = 1. Our results strongly support fairly long range magnetic interactions instead of the generally accepted model covering only nearest and next nearest neighbour interactions.     

Microscopic magnetic properties of nonstoichiometric V2O3+x—NMR and inelastic spin-flip neutron scattering measurements

The local magnetic properties of the V sites in the nonstoichiometric V₂O_3+x (0 ? x <0.08) have been examined by nuclear magnetic resonance and inelastic spin-flip neutron scattering techniques. The samples with x = 0.01 and 0.02 show a paramagnetic metal (PM)-antiferromagnetic insulator (AFI) transition. In the AFI phase, two distinct ⁵¹V NMR signals with hyperfine fields H_n = 184.9±0.5 kOe and 71±1 kOe were observed at 1.8 K, which were assigned as due to V³⁺ and V³⁺ sites, respectively. On the other hand, the samples with x = 0.04 and 0.06 were metallic down to 1.4K, and showed a paramagnetic (PM)-antiferromagnetic (AFM) transition at about 10 K. In these samples, a ⁵¹V NMR signal with H_n = 58±2 k0e and one with 〈H_n〉 = 9kOe were observed at 1.8 K, which were assigned as due to V³⁺-like sites and the matrix V sites, respectively. These results are entirely consistent with those obtained from the neutron experiment. We propose that in the metallic phase (0.04 ? x < 0.08) the minority V⁴⁺-like sites are magnetically localized in the delocalized V matrix and may be responsible for the antiferromagnetic long range order below 10 K.     

57Fe Mössbauer studies of amorphous Pd40(NiFe)40P20 alloys

Zero-field ⁵⁷Fe Mössbauer spectroscopy has been used to study the magnetic properties of an amorphous melt–spun Pd₄₀Ni_40?x Fe _x P₂₀ (x?=?5, 10, 17.5, 20) series. The alloys show quadrupole split doublets at room temperature indicating paramagnetic behaviour. At low temperatures the Mössbauer spectra are sextets due to the onset of long range order. The transition temperatures increase with Fe concentration from 12?±?2 K for Pd₄₀Ni₃₅Fe₅P₂₀ to 42.0?±?2.0 K for Pd₄₀Ni₂₀Fe₂₀P₂₀. The hyperfine field was found to follow $ {\text{Hf}}{\left( {\text{0}} \right)}{\left( {{\text{1 - }}T \mathord{\left/ {\vphantom {T {T_{{\text{c}}} }}} \right. \kern-0em} {T_{{\text{c}}} }} \right)}^{{\text{ $ \beta $ }}} $ over the critical region with the β exponent being close to 0.4.     

On the mixed valence of the chromium ions in the noncollinear ferrimagnetic spinels Mn1−xCuxCr2S4 (Where x = 0.85, 0.90, 0.95)

For the polycrystalline samples of Mn_1?xCu_xCr₂S₄ (x = 0.85, 0.90, 0.95) the magnetization was measured in the temperature range between 77 K and the Curie temperature, T_C, using a magnetic balance (Faraday's method) and pulsed magnetic fields up to 2.0 T. The magnetic susceptibility was measured between T_C and about 600 K. The Curie temperatures were obtained using the kink point method.In the temperature range between 4.2 and 77 K the magnetization was measured in stationary magnetic fields up to 14 T. The data indicate a noncollinear ferrimagnetic structure. The compounds under investigation can be treated as CuCr₂S₄ slightly doped with Mn, with a valence distribution Mn²⁺_1?xCu¹⁺_xCr³⁺_2?xCr⁴⁺_xS^2?₄.     

Gadolinium as a ferromagnetic host for IMPAC experiments

The properties of ferromagnetic Gd as a host for IMPAC measurements have been investigated. The transient and internal magnetic fields at Cd, Nd, Sm, Dy, Er, Yb and Hf nuclei recoil implanted into polarized Gd at 80 K have been studied by the IMPAC technique. All available experimental transient field data for Gd have been analysed in the framework of the Lindhard-Winther theory. Empirical values of the parametersv _p andC _ion C _atom have been deduced which give good agreement between experiments and theory. Internal magnetic fields at rare-earth nuclei in magnetized Gd at 80 K have been deduced. The results areH _h.f. (NdGd)=?1370±440 kG,H _h.f.(SmGd)=?1440±120 kG,H _h.f.(DyGd)=1410±400 kG,H _h.f.(ErGd)=2310±420 kG andH _h.f.(YbGd)=?216±32 kG. The signs of these fields are, except for Yb which is in a 2⁺ ionic state, consistent with a ferromagnetic coupling between the 4f spins of the implanted ion and the Gd host. The deduced internal field at Hf in Gd is ?440±90 kG. The observed time-dependent interactions for rare-earth nuclei in ferromagnetic Gd are consistent with the Abragam-Pound theory. For the Cd isotopes,g-factors of the first 2⁺ states were deduced from the experiments. The results areg(¹¹⁰Cd)=0.49±0.11,g(¹¹⁴Cd)=0.34±0.09 andg(¹¹⁶Cd)=0.41±0.11. The use of transient magnetic fields forg-factor measurements on high-spin rotational states is discussed.     

Giant hyperfine field at the antimony site in the Heusler-alloy Pd2MnSb

The magnetic hyperfine field at ¹²¹Sb in Pd₂MnSb has the anomalously large value (at 100 K) of ±579 ±5 kG. In the closely related compound PdMnSb we find ±302 ±5 kG, similar to other ferromagnetic intermetallics containing Mn and Sb.     

Magnetic order in palladium-based Heusler alloys Part I: Pd2MnIn1−xSnx and Pd2MnSn1−xSbx

Magnetization, susceptibility, X-ray and neutron diffraction measurements have been made on the two series of alloys Pd₂MnIn_1?xSn_x and Pd₂MnSn_1?xSb_x, for 0 ? x ? 1. All were single phase and were chemically ordered intermetallic compounds with the Heusler L2₁ structure in which the Mn atoms occupy an f.c.c. sub-lattice. At all compositions the alloys were magnetically ordered with a moment of ～4.3 μ_B located at the Mn sites. At the In-rich end the magnetic order is antiferromagnetic f.c.c. type 2. As Sn is increasingly substituted for In there is a change in magnetic order first to antiferromagnetic f.c.c. type 3A and then to ferromagnetism. All the alloys in the Sn/Sb series are ferromagnetic and in both series there is an increase in the ferromagnetic exchange interactions with increasing electron concentration.     

4f ground state properties of cerium in AuCu3 intermetallic compounds studied by x-ray absorption spectroscopy

L_III absorption edges of cerium in ternary AuCu₃ compounds Ce(Pd_1?xM_x)₃ (M = Ag and Rh) and (Ce_1?xY_x)Pd₃ are presented. We find that Ce in these compounds is mixed valent with n_f ? 0.7. The valence V of Ce(Pd_1?xRh_x)₃ becomes concentration independent of V = 3.29 ± 0.02 for x ? 0.18. In Ce_1?xY_xPd₃ we observe the valence to increase up to V = 3.32 ± 0.02 at the highest concentration of Y. We show, that a critical volume, available for the Ce atom, is associated with the concentration independent valence around 3.3. For both systems, linewidths W₁, W₀ and Δ = E(4f¹) ? E(4f⁰), as derived from L_III double-bump structure, are given. Possible falsifications due to “final states effects” on the valence are discussed.     

Interaction of slow neutrons with natural Rutenium,Rhodium, Cadmium and Thallium and some of their isotopes

By means of Christiansen filter technique the following bound coherent neutron scattering lengths were obtained:^natRu:b=7.02 ± 0.02 fm¹⁰⁸Cd:b=5.31 ± 0.24 fm¹⁰³Rh:b=5.90 ± 0.04 fm¹¹⁰Cd:b=5.78 ± 0.08 fm^natTl:b=8.773 ± 0.015 fm¹¹¹Cd:b=6.47 ± 0.08 fm²⁰³Tl:b=8.51 ± 0.08 fm¹¹²Cd:b=6.34 ± 0.06 fm²⁰⁵Tl:b=8.87 ± 0.07 fm¹¹⁴Cd:b=7.48 ± 0.05 fm¹¹⁶Cd:b=6.26 ± 0.09 fm In combination with some total cross section measurements with neutrons in the eV-energy range and with the compiled resonance parameters we deduced consistent sets of spin state scattering lengths and potential radii.     

Nuclear magnetic resonance in icosahedral Al-Pd-Mn alloys

²⁷Al and⁵⁵Mn nuclear magnetic resonance shift,K, and²⁷Al spin lattice relaxation time,T ₁, have been measured for the six-dimensional face-centered icosahedral quasicrystals, Al_75-x Pd₁₅Mn_10+x withx=0, 2 and7. The Al₇₅Pd₁₅Mn₁₀ quasicrystal exhibits a temperature independent Knight shiftK and(T ₁ T)^–1=0.022±0.002 (K s)^–1 in a temperature range from room temperature to 5 K because there exist no Mn atoms with local magnetic moment. The replacement of Al with Mn drastically decreases the²⁷AlK, the⁵⁵MnK andT ₁ of²⁷Al, andthe²⁷AlK becomes negative. There is an additional contribution to the spin lattice relaxation time independent of temperature. This is considered to be due to the presence of a localized magnetic moment in the replaced Mn atoms.     

Magnetic cluster developement in In1−x Mn x Sb semiconductor alloys

X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and magnetic measurements as a function of applied magnetic field and temperature for In_1?x Mn _x Sb (0.05≤x≤0.2) system are reported. Magnetic measurements performed at high and small magnetic field in ZFC and FC indicate the coexistence of ferromagnetic In_1?x Mn _x Sb solid solution and two types of magnetic cluster: ferromagnetic MnSb and ferrimagnetic Mn₂Sb. XPS valence band and Mn 2p core level spectra have confirmed the presence of MnSb and Mn₂Sb phases. TEM images show some manganese antimonide phase microinclusions with dimension between (30–40) nm.     

Polarised neutron diffraction study of Mn1.09Sb

In order to study the influence of interstitial site occupancy on the electronic structure of MnSb, a polarised neutron diffraction experiment was performed on Mn_1.09Sb. The composition of the sample was obtained from the refinement of single crystal neutron diffraction data. The polarised neutron diffraction experiment yielded unpaired electron populations of the levels a^t_1g, e_g^t and e_g as follows: μ_x0 = 0.57 μ_B, μ_x± = 1.60 μ_B, μ_u± = 1.28μ_B. The comparison of these numbers with results of Yamaguchi et al shows that the spin density for this composition is reduced for the low energy level a^t_1g. This finding is interpreted by an occupation of minority spin states by electrons of the interstitial Mn atoms. In agreement with this, increasing Mn excess leads to a decreasing magnetic moment magnitude/Mn-atom and to a contraction of the lattice parameter c, indicating the strengthening of the Mn-Mn bond in [001].     

Peculiarities of the band magnetism in the higher manganese silicide

Magnetism of MnSi_x, x=1.746 (Mn₂₇Si₄₇) was investigated by SANS, neutron diffraction, magnetization and magnetic susceptibility measurements. MnSi_x single crystalline specimens were characterized by X-ray and neutron diffraction. A spiral spin structure with periodicity ?=(163±4) Å along the c axis and a spiral component of the magnetic moment per Mn of p_o=0.056 was determined. From the field dependence of ? it is indicated that the magnetic order below T_N=42 K is an incommensurate state. From the large difference of the magnetic moments in the paramagnetic state and ordered state MnSi_x is classified as an itinerant magnet. Below T_N the difference of the magnetic moments per Mn between p_o=0.056 at H = 0 from SANS and p_s = 0.014 at saturation field from magnetization measurements is explained by longitudinal spin fluctuations.     

Magnetization and spin-flip energy in Cd0.9Mn0.1Se

Magnetization and spin-flip Raman measurements are reported for Cd_1?xMn_xSe, x = 0.106, at 1.9 < T < 4.2 K and magnetic fields H up to 80 kOe. The high-field results are combined to determine the exchange energy between donor electrons and Mn⁺⁺ spins, αN₀=261±13 meV. Empirical fits to the magnetization data are described.     

Hyperfine magnetic fields on Cd impurity in the Pd2MnIn1-xSnx and Pd2MnSn1-ySby heusler alloys

The TDPAC technique was used to measure the magnetic hyperfine field (mhf) acting on Cd impurity in the Heusler alloys Pd₂MnIn_1-xSn_x and Pd₂MnSn_1-ySb_y for various values of x and y in the range 0 ? x, y ? 1. The alloys of Pd₂MnIn_1-xSn_x are antiferromagnetic at the In-rich end and ferromagnetic at the Sn-rich end, with a transition region x ≈ 0.5?0.7 where both phases coexist; the alloys containing Sn/Sb are ferromagnetic for all values of y. The mhf on the Cd impurity in the antiferromagnetic, transition and ferromagnetic regions of Pd₂MnIn_1-xSn_x are respectively zero, -150 and -200 kOe. For the Sn/Sb alloys the field changes from -200 at the Sn-rich end to -235 kOe at the Sb-rich end. The values of the field very closely follow the trend of the ferromagnetic Curie temperatures for the same alloys as a function of the s-p electron concentration. The observed large distribution of field intensities (～20%) and the lower values of the field in the region x = 0.5?0.6 are attributed mainly to the effect of antiferromagnetic domains. The results are compared with previous Mössbauer mhf measurements at the sites of Sn and Sb in the same alloys as well as with measurements in other Heusler alloys.     

Ionic conductivity of Zr1−xIn2xO2−x

As x in Zr(In)O_2?x is increased from 0.08 to 0.16 (9–19 mole per cent In₂O₃) the activation energy E(x) for ionic conduction increases from 1.05 to 1.51 eV; the concuctivity decreases from 2 × 10^?5 to 3 × 10^?6Ω^?1cm^?1at 400°C, is composition-independent at about 580°C, and increases from 1 × 10^?2 to 4 × 10^?2Ω^?1cm^?1 at 800°C. The pre-exponential term of the Boltzmann-type conductivity equation depends exponentially on E(x), a much stronger dependence on x than theoretically expected with a model for ionic conductivity that includes nearest-neighbor defect interactions. Analysis of reported conductivity data for Zr(M)O_2?x (M = Sc, Y, Ca and rare earth metals) and other doped oxide electrolytes with fluorite-type structure reveals that the same relationship is observed with these materials when x γ0.08. It is shown that ionic conduction in these oxides is consistent with nearest neighbor vacancy-cation defect interaction forx < 0.08 but that an additional complex interaction with composition-dependent free energy ΔG(x) occurs when xγ 0.08.The lattice constant of Zr(In)O_2?x with the cubic fluorite-type structure is independent of composition, 5.114 ± 0.002 Å, in agreement with ionic size considerations.