Mn In Samples Research Articles

EPR and photoluminescence studies of ZnO:Mn nanophosphors prepared by solution combustion route

Nanocrystalline ZnO:Mn (0.1 mol%) phosphors have been successfully prepared by self propagating, gas producing solution combustion method. The powder X-ray diffraction of as-formed ZnO:Mn sample shows, hexagonal wurtzite phase with particle size of ∼40 nm. For Mn doped ZnO, the lattice parameters and volume of unit cell ( a = 3.23065 Å, c = 5.27563 Å and V = 47.684 (Å) 3) are found to be greater than that of undoped ZnO ( a = 3.19993 Å, c = 5.22546 Å and V = 46.336 (Å) 3). The SEM micrographs reveal that besides the spherical crystals, the powders also contained several voids and pores. The TEM photograph also shows the particles are approximately spherical in nature. The FTIR spectrum shows two peaks at ∼3428 and 1598 cm −1 which are attributed to O–H stretching and H–O–H bending vibration. The PL spectra of ZnO:Mn indicate a strong green emission peak at 526 nm and a weak red emission at 636 nm corresponding to 4T 1 → 6A 1 transition of Mn 2+ ions. The EPR spectrum exhibits fine structure transition which will be split into six hyperfine components due to 55Mn hyperfine coupling giving rise to all 30 allowed transitions. From EPR spectra the spin-Hamiltonian parameters have been evaluated and discussed. The magnitude of the hyperfine splitting ( A) constant indicates that there exists a moderately covalent bonding between the Mn 2+ ions and the surrounding ligands. The number of spins participating in resonance ( N), its paramagnetic susceptibility ( χ) have been evaluated.

Analysis of volume distribution of power loss in ferrite cores

We present a technique to estimate the inhomogeneities of magnetic loss across the section of ferrite cores under ac excitation. The technique is based on two distinct calorimetric methods that we presented elsewhere. Both methods are based on the measurement of the rate of increase of the sample temperature under adiabatic condition. The temperature ramp is recorded either measuring the sample bulk resistivity or using a platinum probe pasted on the sample surface. As an example we apply the procedure to an industrial sample of Mn–Zn ferrite under controlled sinusoidal excitation with a peak induction of 50 mT in the range between 100 kHz and 2 MHz. The results are discussed by comparison with simulations of the dissipation field profile through the sample, calculated using a finite element method (FEM) code.

Composition and structure of nanocrystalline Fe and Mn oxide cave deposits: Implications for trace element mobility in karst systems

Fe and Mn oxides are ubiquitous, highly reactive minerals in the environment which often control the distribution and speciation of trace elements in soils and aquatic systems. Pautler Cave in Southwest Illinois contains Fe and Mn oxide deposits with properties that differ spatially and temporally. Two depositional environments exist in the cave: Fe and Mn precipitation where anoxic groundwater enters the oxic cave passage (seep deposition) and direct deposition from the cave stream. Seep waters have higher concentrations of Ca 2+, Fe 2+, and Mn 2+, lower pH, and lower O 2(aq) concentrations relative to stream waters. In addition, seep waters have nearly constant δ 18O values that are similar to the yearly average of local precipitation, whereas cave stream waters have more erratic δ 18O values and appear to be influenced by seasonal variations of δ 18O in rainfall. These differences suggest that the seep water source has a longer residence time in the subsurface than the cave stream water. Fe oxides are solely found as seep deposits whereas Mn oxides are deposited both by groundwater seepage and cave streams. Freshly precipitated Fe oxides are composed of ferrihydrite and filamentous material consistent with biomineralization structures of the microbial genera Gallionella and Leptothrix. Mn oxide minerals consist of 7 and 10 Å phyllomanganates having a range of three dimensional order. Mn oxide samples show a greater heavy metal and trace element content compared to Fe oxides, and Mn oxides deposited by cave streams have higher concentrations of metals than Mn oxide seep deposits. In addition, phyllomanganate particle morphologies and crystallinity display a compositional dependence, with platelet size and phyllomanganate sheet stacking-order decreasing with increasing Ba and trace element content and decreasing Ca content; these properties also appear to correlate with dissolved Mn(II) in the source water. These observations suggest that Fe and Mn oxide minerals in oxic cave systems affect trace element concentrations in carbonate-fed springs, and illustrate a previously unrecognized limitation on the transport of inorganic nutrients and contaminants in karst aquifers.

EPR and magnetic quantum tunneling studies of the mixed valent [Mn 4(anca) 4(Hedea) 2(edea) 2]·2CHCl 3, EtOH single-molecule magnet

High-frequency Electron Paramagnetic Resonance (EPR) and Quantum Tunneling of Magnetization (QTM) measurements have been carried out on single-crystal samples of a mixed-valent Mn 2 II Mn 2 III single-molecule magnet (SMM). Frequency, temperature and field-oriented studies reveal an S = 9 spin ground state with low-lying excited spin states. Numerical simulations were performed via exact diagonalization of a multi-spin Hamiltonian, in which the anisotropy of the molecule is based on the anisotropy of the individual ions and their couplings. We found that the EPR and QTM spectra may adequately be explained with two s = 5/2 Mn II ions weakly coupled to a rigid s = 4 spin, formed by the two ferromagnetically coupled Mn III ions.

(Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties

(Zn(1-x-y)Mg(y))(2)GeO(4): xMn(2+) (y = 0-0.30; x = 0-0.035) phosphors with uniform submicrorod morphology were synthesized through a facile hydrothermal process. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the samples. SEM and TEM images indicate that Zn(2)GeO(4):Mn(2+) samples consist of submicrorods with lengths around 1-2 μm and diameters around 200-250 nm, respectively. The possible formation mechanism for Zn(2)GeO(4) submicrorods has been presented. PL and CL spectroscopic characterizations show that pure Zn(2)GeO(4) sample shows a blue emission due to defects, while Zn(2)GeO(4):Mn(2+) phosphors exhibit a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)) under the excitation of UV and low-voltage electron beam. Compared with Zn(2)GeO(4):Mn(2+) sample prepared by solid-state reaction, Zn(2)GeO(4):Mn(2+) phosphors obtained by hydrothermal process followed by high temperature annealing show better luminescence properties. In addition, codoping Mg(2+) ions into the lattice to substitute for Zn(2+) ions can enhance both the PL and CL intensity of Zn(2)GeO(4):Mn(2+) phosphors. Furthermore, Zn(2)GeO(4):Mn(2+) phosphors exhibit more saturated green emission than the commercial FEDs phosphor ZnO:Zn, and it is expected that these phosphors are promising for application in field-emission displays.

MAGNETIC AND ELECTRONIC STRUCTURE STUDIES OF Mn1+xFe2-2xTixO4 (0 ≤ x ≤ 0.5) FERRITES

A series of polycrystalline bulk samples of Mn 1+x Fe 2-2x Ti x O 4 (0 ≤ x ≤ 0.5) have been prepared by using a conventional solid-state reaction method. The effect of Ti4+ ions substitution on magnetic and electronic structure of MnFe2O4 has been studied using isothermal d.c. magnetization and near edge X-ray absorption fine structure spectroscopy (NEXAFS) measurements. The magnetization studies infer that all samples have ferrimagnetic ordering at room temperature. The magneton number (nB) calculated using the magnetic hysteresis loop has been found to decrease linearly with the Ti substitution, which indicates that the system follows the Neel's two sub-lattice model. The decrease in the value of nB may be due to the dilution of the sub-lattice by Ti ions. The NEXAFS measurements performed at Fe/Ti L3, 2 edges indicate that Fe ions are in mixed valence state whereas Ti ions remain unchanged at 4+ state.

YAlO3:Mn nanocrystals obtained in sol‐gel and their properties

AbstractManganese‐doped yttrium aluminum perovskite (YAP) nanocrystalline samples of 0.05 at%, 0.2 at% and the reference single crystal of predicted 0.02 at% Mn, 0.02% Si concentration in YAP were investigated by the following methods: X‐ray powder diffraction, scanning electron microscopy, EPR, SQUID and XPS. These examinations revealed that the obtained material was not single phase and the trace of Y3Al5O12 (YAG) appeared. As is evident from EPR studies, the manganese in all investigated samples is occupying an yttrium site and the valence of manganese remains as Mn2+. The EPR spectra of both powder YAP:Mn samples are the same, an expected difference in the intensity well reflects the nominal concentration of manganese. The single crystal perovskite YAlO3 doped with manganese showed very complex and strongly anisotropic EPR spectrum. The EPR data showed the presence of Mn2+ ions substituting yttrium site and Cr3+ and Fe3+ undesirable impurities which occupied aluminum site. The magnetic moments of manganese calculated for the nanopowders confirmed Mn2+ state. The SEM/EDS and XPS analyses showed the chemical composition of nanopowders as very consistent for both methods. For both samples the lower content of aluminum in relation to the nominal value was found. The SEM images show that the sample 0.2 at% Mn has more agglomerated structure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetic Properties of Some Hydrated Transition Metal Oxide and Hydroxide Nanoparticles Synthesized in Different Media

Nanoscale particle size of metal oxides and hydroxides showed enhanced various physical properties and performance. We established a simple, cost-effective, room-temperature (RT) precipitation method for the preparation of the magnetic, first-raw transition metal (TM) hydrated oxide and hydroxide nanoparticles. This method is based on the use of the TM nitrate, as the metal source, and cyclohexylamine (CHA), as a precipitating agent, either in the water (H2O) or ethanol (EtOH) medium. We found that the precipitation medium and the identity of precipitated TM strongly affect the morphology, particle size, and magnetism of the product. The morphology varies from spherical, to rectangular, to rod shape; while the size varies in the range of 5-30 nm. All samples showed paramagnetic behavior with Curie temperatures span over a wide range (20-150K). Huge hysteresis looses has been observed for manganese (Mn) sample, prepared in H2O. The coercively (Hc) at 4.2K for this sample is about 1.5T, which is comparable to the strongest permanent magnets (Nd-based magnets) available at room temperature. The energy product (Hc*MR) is about 4.5*105 (emu/g)Oe.

A Comparative Study between the Effects of Magnetic and Nonmagnetic Dopants on the Properties of ZnO Varistors

A comparative study between effects of Mn and Al on the properties of ZnO varistor sintered at 1200 is investigated by XRD, SEM hardness, and I-V measurements. Although both Mn and Al do not influence the well-known peaks related to wurtzite structure of ZnO ceramics, some other unknown peaks could be formed at higher doping content (). Also, the shape and size of grains are clearly different for both dopants. Average crystalline diameters, deduced from XRD analysis, are between 42 nm and 62 nm, which are 50 times lower than those obtained from SEM micrographs, while the oxygen vacancies deduced from EDAX analysis, are gradually decreased by doping content for both dopants. Interestingly, the values of breakdown field, nonlinear coefficient and barrier height are found to be higher in Mn samples as compared to Al samples, while the opposite is reported for leakage currents, hardness, and electrical conductivities. The values of are changed from 2.67 V/cm to 41.67 V/cm for Al, and from 1928 V/cm to 6571 V/cm for Mn. The conductivity of Al samples is higher than that of ZnO, and it is nearly (103–105) times the conductivity of Mn samples. These results are discussed in terms of the difference of magnetic moment and valence state between these two additives.

Ag and Ag–Mn nanowire catalysts for alkaline fuel cells

Low loadings of Ag and Ag–Mn nanowire catalysts were applied to the surface of a CNT-base electrode. The catalyzed electrodes had a 60 mV larger onset potential and promoted the ORR via the direct 4 electron pathway. The Ag/CNT, Ag–Mn/CNT, and CNT samples produced a Tafel slope of about 70 mV/decade which confirmed the ORR activation was limited by the migration of oxygen molecules to active surface sites. The catalytic performance of the Ag and Ag–Mn nanowires was also comparable to that of a bulk catalyst but at a much lower loading. Electrochemical test results showed that the Ag and Ag–Mn catalysts exhibited similar performance. The Ag–Mn nanowire catalysts were synthesized using a unique electroless deposition procedure to co-deposit Ag and Mn. ICP confirmed that 2 to 9 at% Mn was present in the nanowires. XPS and XRD analysis showed that the Ag–Mn nanowires were composed of Mn in solid solution with Ag and a thin surface layer containing MnO and MnO 2. The Ag–Mn nanowires were expected to be the most active. The equivalent performance between Ag and Ag–Mn samples was attributed to the presence of inactive MnO and low concentrations of MnO 2 in the nanowires. Although MnO 2 is known to be active towards the ORR, the dominant Mn species in the nanowires was MnO.

Oriented Grain Growth Analyses With In Situ Annealing Experiments Using High Energy Synchrotron Radiation

AbstractThe development of the recrystallization and annealing textures of Al–Mn alloys with 0.4, 0.7 and 1 wt.‐% manganese is analyzed using specific techniques that allow the detection of changes in grain orientation during in situ annealing. In order to investigate the evolution of texture components during annealing, highly rolled samples were annealed from room temperature to 500 °C at a constant heating rate. The advantage of in situ annealing experiments using synchrotron radiation is the detection of grain orientations over time, which allows observation of the development of the recrystallization and annealing textures in a sample. In fact, the recrystallization and annealing textures in the Al–0.4Mn are characterized by an interruption in the detection of most of the grain orientations between 380 and 425 °C and by competition between the cube {001}<100>, {011}<1‐33>, {011}<0‐11> and rotated‐cube {001}<110> grain orientations, where the latter is detected until the end of the experiment. In the Al–0.7Mn sample a competition between the cube {001}<100>, {011}<100>, and rotated cube {001}<110>, {011}<0–11> grain orientations is observed. In the sample with the highest manganese concentration (1 wt.‐%) an unhindered grain growth of all possible grain orientations with a high amount of the {011}<0‐11> grain orientation is observed. The evolution of the resulting local textures is discussed in terms of preferentially oriented grain growth depending on the temperature and manganese concentration.

Physical and Electrical Properties of Nanosized Mn‐ and Cr‐Doped Strontium Y‐Type Hexagonal Ferrites

Nanometer‐sized crystallites of Y‐type strontium hexaferrite, Sr2Ni2Fe12O22 and its Mn‐ and Cr‐doped derivatives have been synthesized by the sol–gel method. Y‐type phase formation was achieved at a considerably lower temperature of 950°C than is required in the traditional solid‐state method (1200°C). The effect of doping of manganese at the tetrahedral site, Sr2Ni2−xMnx Fe12O22 (x=0.0–2.0), and chromium at octahedral site, Sr2Ni2 Fe12−yCryO22 (y=0.0–1.5), has been studied. The crystal structure remains unaffected by the substitutions. The crystallite size in the range of 13–45 nm is calculated from the X‐ray diffraction data. The energy‐dispersive X‐ray fluorescence analysis shows that Y‐type hexaferrites can be prepared with a base of strontium. The extent of doped Cr+3 ions at the octahedral site has been increased from the reported maximum value of y=1.5. Scanning electron micrographs of the samples showed a homogenous microstructure. The dc electrical resistivity studies show that these hexaferrites exhibit high resistivity at room temperature. Cr‐doped samples have comparatively higher resistivity than Mn‐doped samples. The doubly doped (Cr+Mn) samples possess high resistivity (7.37 × 109Ω‐cm), a low dielectric constant (33.88 at 3000 Hz), and a high Curie temperature (>698 K). The dielectric energy losses are minimized by increasing the Mn and Cr contents of the synthesized samples.

The effect of thermal treatment on the magnetic state and cluster-related disorder of icosahedral Al–Pd–Mn quasicrystals

The evolution of the magnetic state and the cluster-related disorder upon thermal treatment of the icosahedral i-Al–Pd–Mn quasicrystals were studied on single-crystalline samples subjected to different thermal annealing sequences involving short and long annealing times and slow or fast cooling modes. In this way, thermal equilibration of the samples was systematically changed by varying the amount of vacancies and thermal strains. The results show that different thermal treatments can reduce or increase reversibly the paramagnetic magnetization of the i-Al–Pd–Mn samples of nominally the same composition by a factor up to 26. Magnetic susceptibility and magnetization measurements have demonstrated comparable importance of the vacancies and thermal strains on the size of the mean effective magnetic moment per Mn atom. While the reduced vacancy concentration reduces the mean effective moment, thermal strains induced by rapid cooling increase it. Theoretical ab-initio calculations of the effect of vacancies and thermal strains on the magnetic properties of a periodic approximant model to the i-Al–Pd–Mn phase predict that vacancies at specific Al sites introduce magnetic moments at the Mn sites, which are otherwise nonmagnetic in the perfect structure. Removal of thermal strains by relaxation of the structure containing vacancies acts in the opposite way by decreasing the moments. X-ray diffraction experiments with full reciprocal space sampling revealed that the cluster-related disorder cannot be improved noticeably by annealing at either 800 °C or 600 °C even for annealing times as long as three months, suggesting that this disorder may be intrinsic to the i-Al–Pd–Mn phase, needed for the electronic or entropic stabilization of the structure.

Complete n-hexane oxidation over supported Mn–Co catalysts

Two series of Co–Mn samples were prepared by impregnation of silica with aqueous solutions of Co(NO3)2·6H2O and/or Mn(NO3)2·6H2O. Cobalt oxide was the predominant phase in one of the series and manganese was used as the promoter. The major component in the second series was manganese oxide and Co was the promoter. The prepared samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) and tested in the reaction of complete n-hexane oxidation. The catalytic activity of both single component cobalt and manganese samples was similar, however, a combination between the two elements changed significantly the activity and this depended on the method of preparation. Catalysts prepared by a common solution of Co- and Mn nitrates manifested a considerable increase in activity as a result of very low crystallinity of the supported metal oxide phases, partial enrichment of the surface with cobalt and uniform distribution of oxide agglomerates on the support.

Characterization and TSL dosimetric properties of Mn doped BaSO 4 phosphor prepared by recrystallisation method

Mn doped BaSO 4 powders were prepared by recrystallisation method and the formation of the compound was confirmed by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and scanning electron microscopic (SEM) studies. The thermally stimulated luminescence (TSL) studies of Mn doped BaSO 4 sample (doping concentration is 0.5 mol%) showed glow curve having two glow peaks at 147 and 225 °C after heating at a constant heating rate of 4 °C/s. Comparison of TL intensity of the most intensive glow peak of Mn doped BaSO 4 compound with that of undoped BaSO 4 shows that the addition of Mn impurity in BaSO 4 compound enhances the thermoluminescence (TL) intensity by about 3 times. The trap parameters associated with the glow peaks in X-irradiated BaSO 4:Mn sample were obtained by glow curve shape method. The thermoluminescence dose response, reproducibility and fading of the BaSO 4:Mn phosphor were also studied.

Synthesis of undoped and M-doped ZnO (M = Co, Mn) nanopowder in water using microwave irradiation

Undoped and M-doped ZnO (M = Co, Mn) nanopowders have been successfully synthesized by microwave-assisted approach using Zn(NO3)2.2H2O and NaOH. The results obtained from X-ray diffraction (XRD) analysis and the transmission electron microscopy (TEM) showed that the mean particle size was about 10–15 nm. The XRD analysis of the synthesized samples also showed a single phase ZnO structure without any additional phase. Magnetic property studies of the as-prepared M-doped ZnO (M = Co, Mn) samples showed them to be paramagnetic material. However, thermal annealing in air of particular samples at 800°C for 3 h resulted in transforming the samples into a room temperature ferromagnetic material.

Room temperature ferromagnetism in Mn doped dilute ZnO semiconductor; an electronic structure study

Confronting reports of room temperature ferromagnetic ordering in bulk as well as thin films of dilute doped semiconductors motivated us to prepare and study some dilute Mn-doped (2% and 4%) ZnO polycrystalline pellets. Our aim was to find out how the changes in the electronic structure can correlate to the observed magnetic properties in such diluted magnetic semiconductor materials. The 2% Mn sample shows above room temperature magnetic ordering with further enhancement in magnetic properties upon cooling. The magnetic ordering gets completely quenched for 4% Mn doping at room temperature and no evidence of ordering found even down to 5 K. The electronic structure of these two samples has been investigated using Mn L23 X-ray absorption spectroscopy, Zn 2p and 3p, Mn 3p and O 1s X-ray photoemission spectroscopy. Our results show that overall the manganese shifts toward the higher valence state upon Mn doping while there is no change in the zinc and oxygen valence. The concentration of divalent Mn state is found to be much higher in the ferromagnetic sample (Mn=2%). For the non-ferromagnetic sample a larger contribution of higher oxidation Mn states is present and also the oxygen content is found to be higher. These two factors have been correlated to the suppressed ferromagnetism but it is difficult to predict their relative weights.

Characterization of (Mn, Co)-Codoped ZnO Nanorods Prepared by Thermal Diffusion

We prepared (Mn, Co)-codoped ZnO nanorods by thermal diffusion using pure ZnO nanorods, Mn and Co fragments as precursors. Detailed investigations of X-ray diffraction, electron microscopy, photoluminescence and Raman scattering spectroscopy revealed the incorporation of dopants Mn and Co into the ZnO host lattice. This did not change much the lattice parameters of ZnO, and not lead to the development of secondary phases related to the dopants. Compared with magnetic behaviors of two reference samples of Mn- and Co-doped ZnO nanorods, we observed the decrease of magnetic ordering in (Mn, Co)-codoped ZnO nanorods. This could be explained that magnetic interaction between Mn and Co ions is antiferromagnetic.

Oxygen Reduction Electrode Properties of Manganese Oxide Nanosheet-Based Materials

Two types of oxide nanosheet-based materials, H3O+-form regularly stacked manganese oxide nanosheets (H3O+-RG(Mn)) and H3O+-form randomly restacked manganese oxide nanosheets (H3O+-RE(Mn)) were synthesized by soft chemical methods, and their oxygen reduction reaction (ORR) activities were examined by cyclic voltammetry (CV) and semi-steady-state voltammetry (SSV) with a rotating ring-disc electrode at 70 °C in 0.1 M KOH. Both samples showed high onset potentials (Eon) of the ORR current and high efficiencies (Eff4) of the 4-electron reduction of oxygen, and Eon and Eff4 values were improved by electrochemical oxidation up to 1.2 V (vs. reversible hydrogen electrode) in the CV measurement prior to the SSV measurement. As a result, the nanosheet-based samples exhibited higher ORR activities than the starting materials, K+-form layered manganese oxide K0.5MnO2 (K+-RG(Mn)) and Mn2O3, and a well-known ORR catalyst, MnO2. The H3O+-RE(Mn) sample electrochemically oxidized up to 1.2 V showed the highest ORR activity, Eon = 0.97 V and Eff4 = 99%, which were comparable to those of a conventional 20 mass% Pt/C catalyst. The comparison of their ORR activities, BET surface areas and X-ray photoelectron spectra suggests that the enhancement of the ORR activity is attributed to an increase in the numbers of the ORR active sites and a large amount of H2O in the interlayers and on the surface of the nanosheets because of rapid of H2O-supply enough for ORR in alkaline solution.

Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part II. Correspondence of structural change to irregular variations of partitioning coefficients and tetrad effect variations appearing in interatomic distances

Experimental distribution coefficients of rare earth elements (REEs) between Fe oxyhydroxides (FeOOH) and Mn dioxide (δ-MnO2) and solutions [ K D(REE)] exhibit anomalous variations: preferential uptake of light REEs by Mn dioxide, a step-like trend in K D(REE) in the Er-Tm-Yb-Lu region, and fractionation of K D(Y) from K D(Ho). Extended X-ray absorption fine structure (EXAFS) spectroscopy was applied to determine coordination states of Er, Tm, Yb, Lu, and Y adsorbed onto FeOOH and δ-MnO2 to assess structural changes around the REE site. The structures obtained, combined with previously determined structures of light REEs-sorbed Fe and Mn samples, corresponded to variations found in K D(REE). The structural parameters in the first coordination sphere suggest that La, Pr, and Nd adsorbed onto δ-MnO2 have a distorted tenfold-coordination sphere and differ greatly from La-, Pr-, Nd-, and Sm-sorbed FeOOH, which have a mixture of eightfold- and ninefold-coordination spheres. In contrast, heavy REEs including Y adsorbed onto Fe and Mn samples’ local structures have an eightfold-coordination sphere. The preferential uptakes of light REEs by δ-MnO2 are explained by the structural change. The irregular variations of heavy REEs and Y fractionation from Ho in K D(REE) do not, however, correspond to any change found in the coordination sphere. During characterization of the first coordination sphere, the W-type tetrad effect appears in the series variation of interatomic distances of REEaq3+ and REE-sorbed FeOOH and δ-MnO2. The occurrence of a tetrad effect indicates that the interatomic distances relate not only to the electrostatic field but also to a quantum field.