Dy Site Research Articles

Theoretical investigation of magnetic and thermal properties in Dy1−x Sc x Ni2 series

We report on the thermal and magnetic properties of Dy1−xScxNi2 series compounds (x=0.1,0.3,0.5,and0.7), which were investigated through a model Hamiltonian including the exchange, Zeeman, and crystalline electric field interactions. We investigated the effect of Sc substitution on the Dy site on the magnetic and magnetocaloric properties of these compounds. Theoretical results were simulated for heat capacity, entropy, and the magnetocaloric effect quantities. Our model reproduced the decrease of the magnetic ordering temperature and of the isothermal entropy change peaks as Sc concentration increases. Our theoretical results were confronted with experimental data from the literature, showing good agreement.

Impact of organic matter on arsenic mobilization induced by irrigation in the unsaturated and saturated zones

Organic matter (OM) plays an important role in the biogeochemical transformation of arsenic (As) in groundwater and sediments. High-As groundwater used for irrigation introduces dissolved As into the ground. Moreover, water table fluctuations and variations in redox conditions affect As mobilization in both the unsaturated and saturated zones. A field experiment was conducted at the DY site, Datong Basin, China to explore the effect of OM on As and iron (Fe) mobilization and transformation in the unsaturated and saturated zones during irrigation. Soil water/groundwater and sediments sampled at different depths during the experiment were analyzed to investigate the hydrochemical processes and correlations between As, Fe, and OM concentrations. Irrigation activities led to the accumulation of aqueous As in the saturated zone and increasing As content in the topsoil. Analyses of Fourier-transform infrared (FTIR) spectra suggest the existence of As-Fe-OM ternary complexation. Parallel factor analysis (PARAFAC) of the three-dimensional fluorescence excitation–emission matrix (EEM) reveals that water-extractable organic matter (WEOM) of sediments comprises three major components, two terrestrial humic-like components (C1 and C2) and one protein-like component (C3). And terrestrial humic-like components with high molecular weight promotes As-Fe-OM complexation reactions. The results of this study demonstrate As mobilization under irrigation conditions and contribute to a better understanding of the role of OM under high-As groundwater irrigation. This study has implications for controlling and managing OM or As-contaminated water for irrigation in high-As groundwater regions.

Comparison of N2O Emissions From Cold Waterlogged and Normal Paddy Fields

Paddy fields are major sources of atmospheric N2O. Soil temperature and moisture strongly affect N2O emissions from rice fields. However, N2O emissions from cold-waterlogged paddy fields (CW), an important kind of paddy soil in China, are not well studied so far. It is unclear whether the N2O emissions from cold-waterlogged paddy fields are the same as normal paddy fields (NW). We investigated the N2O emission characteristics from the CW and NW paddy fields under with (R1) and without (R0) rice in Tuku Village, Baisha Town, Yangxin County (YX site, monitoring in 2013) and Huandiqiao Town, Daye City (DY site, monitoring in 2014); compared the difference and influencing factors between the CW and NW paddy fields at two sites in South China. The results showed that the N2O emissions from NWR0 were 13.4 times higher than from CWR0, and from NWR1 were 10.3 times higher than from CWR1 in the YX site. The N2O emissions from NWR0 were 2.4 times higher than from CWR0, and from NWR1 were 17.3 times higher than from CWR1 in the DY site. The structural equation models (SEMs) showed that the N2O emissions are mainly driven by rice planting and soil moisture in the NW fields at the annual scale, while soil temperature in the CW fields. Overall, N2O emissions from cold waterlogged paddy fields are significantly lower than those of normal paddy fields due to the low temperature and higher water content; however, there are dinitrogen emissions from cold waterlogged paddy fields denitrification should be further examined.

Magnetic and electric behaviors of [formula omitted]: Effect of hole doping

DyMn2O5 is an intriguing multiferroic material showing multiple magnetic, electric and structural transitions. We present here the systematic study on the effect of Sr doping at the Dy site of DyMn2O5 through magnetic and dielectric measurements. Doping of divalent Sr at the Dy site is expected to enhance the Mn4+:Mn3+ ratio and it will also dilute the Dy site. Our study indicates large enhancement in the magnetic anomaly observed close to 43 K, which we believe to be related to the increased ferromagnetic correlations on Sr doping. Gradual increase in coercive field at 3 K with the Sr doping and decrease in bond length of adjacent Mn4+ ions further support the enhancement of ferromagnetic correlations in the system. The parent sample shows a large magnetocaloric effect around 12 K, the magnitude of which found to decrease with increasing Sr concentration. The doping also enhances the anomaly at around 28 K observed in the dielectric permittivity versus temperature data, and this anomaly was earlier claimed to be associated with the spin reorientation as well as a simultaneous transition from one ferroelectric state to other. The electric orderings observed below 25 K are found to be susceptible to the applied magnetic field, and supports the view of Ratcliff II et al. (Phys. Rev. B 72, 060407(R) (2005)) of concomitant changes in the magnetic structure associated with the multiple electric transitions.

Evidence for ferromagnetic clusters at room temperature in Dy and Mn site co-substituted compounds: Dy0.55Sr0.45Mn1-xFexO3

Polycrystalline compounds of Dy0.55Sr0.45Mn1-xFexO3 (x = 0.0–1.0: 0.2) were prepared by high temperature solid state reaction route. All the compounds were found to have orthorhombic structure with Pnma space group with four formula units per unit cell. However, for high iron content corresponding to 0.8 and 1.0, some impurity phases were present. Raman modes of the substituted compounds were found to shift to higher wave numbers as compared to x = 0.0. All the compounds displayed insulating property with variable range hopping type of conduction. Mössbauer spectroscopy studies performed at room temperature revealed the presence of both trivalent and tetravalent iron ions for high concentrations of iron. Sextet pattern observed for high iron content suggested the presence of a magnetic phase even at room temperature. Temperature variation of magnetization showed paramagnetic behavior in the high temperature region (>100 K) and displayed variety of magnetic structures below 100 K. Effective magnetic moments (μeff.) of the compounds were determined by fitting the molar susceptibility data in the paramagnetic state to Curie-Weiss law. Experimental effective magnetic moment values were found to be larger than the calculated μeff. values revealing ferromagnetic cluster formation.

Effect of A-site Fe substitution on the magnetic behavior of Dy2Ti2O7 spin ice

Abstract Geometrically frustrated Dy2Ti2O7 spin ice is known for robust magnetic behavior where structural and dielectric properties are coupled with its magnetism. Herein, effects of Fe substitution, at the magnetic Dy site (0 ≤ x ≤ 0.15) in Dy2Ti2O7 compound have been systematically examined in terms of structural distortions and magnetic perturbations through structural, dielectric, optical and magnetic studies. The experimental findings suggest that Fe substitution does not change the crystal electric field acting on the rare earth ion, though it produces significant structural distortions. These findings suggest that spin dynamics non-monotonically depends on the nature and dynamics of neighboring magnetic ion’s spin (Fe spin in this case), because of existing strong spin correlations. This dependency provides a new possibility to tune or modify the spin dynamics of the correlated magnetic states in these materials via magnetic perturbations, which can be controlled by the externally applied magnetic field.

Temperature dependent magnetic properties of Dy-doped Fe16N2: Potential rare-earth-lean permanent magnet

Using the full potential linearized augmented plane wave method, we explored the magnetocrystalline anisotropy of Dy impurity doped α″-Fe16N2. Here, we considered two different Dy concentrations (1.56 and 3.125%). We also investigated the temperature dependence of the magnetic properties. The Dy site occupancy was found to be concentration dependent. The magnetic moments of Fe atoms near the Dy impurity was suppressed. However, we found a large magnetic moment in Dy atom (4.85–4.87 μB). Compared with the magnetic anisotropy constant in the pristine α″-Fe16N2 (0.57 MJ/m3), we obtained an enhanced perpendicular magnetic anisotropy. The calculated anisotropy constants in 1.56% Dy doping was 0.97 MJ/m3 while it became 1.27 MJ/m3 in 3.125% Dy doping. The Curie temperature in the pristine structure was about 820 K and it was suppressed to 765 K and 605 K in 1.56% and 3.125% Dy doping. At room temperature (300 K), the coercive field of 3.125% Dy doped system was enhanced almost 50% compared with that of the pure Fe16N2. We also found a maximum energy product of 50.9 MGOe for 3.125% Dy doping at 300 K. Our finding may suggest that the α″-Fe16N2 can be a potential permanent magnet with a lean Dy doping.

Concise Chemistry Modulation of the SMM Behavior within a Family of Mononuclear Dy(III) Complexes

By means of the facile chemistry, structural assembly, and transformation of four mononuclear Dy(III) complexes, Dy(bpad)3·CH3OH·H2O (1), Dy(bpad)2(H2O)2·NO3 (2), [Dy(bpad)2(tmhd)] (3), and [Dy(bpad)2(btfa)] (4) (Hbpad = N3-benzoylpyridine-2-carboxamidrazone, tmhd = 2,2,6,6-tetramethylheptane-3,5-dione, btfa = 3-benzoyl-1,1,1-trifluoroacetone), with distinct architectures and local symmetries were established. The disparity of the coordination geometries around the Dy(III) ion among these complexes impacts the strength of the crystal field and the local tensor of anisotropy ( D) of each Dy site and their relative orientations, therefore giving rise to diverse SIM behaviors with distinguishing relaxation energy barriers of 106.93 K for 1, 52.55 K for 2, 48.16 K for 3, and 51.41 K for 4. The differences of the magnetic property and the magnetic anisotropy for four complexes have been explained by ab initio calculations, which are corresponding to the experimental results.

Exchange Interactions Switch Tunneling: A Comparative Experimental and Theoretical Study on Relaxation Dynamics by Targeted Metal Ion Replacement.

The magnetic relaxation and magnetization blocking barriers of tailor-made homo- and heterodinuclear compounds [Dy2 (opch)2 (OAc)2 (H2 O)2 ]⋅MeOH (1) and [DyMn(opch)2 (OAc)(MeOH)(H2 O)2 ] (2), where H2 opch is (E)-N'-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide, were systematically investigated and the change in single-molecule magnet behavior originating from targeted replacement of one dysprosium site in the Dy2 compound with manganese was elucidated through a combination of experimental and theoretical studies. A detailed comparative study on these closely related model compounds revealed remarkable changes of the crystal-field splitting and anisotropy of the Dy site and the total exchange spectrum due to the replacement of Dy by Mn. The blocking barriers of these two compounds, which explain their different relaxation behaviors, were analyzed. The two Ising doublets arising from the magnetic interaction in the case of 1 are strongly uniaxial, with tunneling splittings smaller than 10-6 cm-1 , and this leads to magnetic relaxation at temperatures exceeding the exchange energy (2.14 cm-1 ), which involves transition via the excited states corresponding to local transitions on the excited doublet at the Dy site. The third and fourth exchange doublets in 2 (located at 2.16 and 3.25 cm-1 , respectively) show much larger tunneling splittings (of 10-4 and 10-3 cm-1 , respectively), and thus open an important path for magnetic relaxation.

Magnetic properties of DyFe5−xCoxAl7: Suppression of exchange interactions and magnetocrystalline anisotropy by Co substitution

In 3d−4f intermetallic compounds, a Co substitution for Fe usually strengthens the exchange interactions due to a shift of the Fermi energy to a region of the 3d band with higher density of states. Here, we study the influence of Co on the magnetism of ferrimagnetic DyFe5Al7 using magnetization measurements in static (up to 14 T) and pulsed (up to 58 T) magnetic fields. We find that the homogeneity range of DyFe5−xCoxAl7 is limited to x≤2.5. The Co substitution for Fe produces a strong detrimental effect on the 3d−3d intrasublattice exchange interactions, which leads to a pronounced decrease of the Curie temperature and of the 3d−4f intersublattice exchange field. A reduction of the density of states at the Fermi level might occur due to a broadening of the 3d band. A decrease of the rare-earth contribution to the magnetic anisotropy energy is also observed with increasing Co content. This is attributed to a competition between the Fe and Co contributions to the crystal electric field at the Dy site.

Soil attenuation of the seepage potential of metallic elements (Cu, Zn, As(V), Cd, and Pb) at abandoned mine sites: A batch equilibrium sorption and seepage column study

Soil attenuation of off-site leaching potential of metallic elements at the two abandoned mine sites was investigated using batch sorption and layered column studies. In batch study, the leachate concentration-specific sorption (Kd*) by downgradient clean soils was in the order of Pb>Cu>Cd>Zn>As for DY site and Pb>As>Cu>Cd>Zn for BS site. In the layered (mine+clean) soil column, element elution was significantly reduced (e.g., no initial flush, retarded peak arrival, and lower peak concentration) while sulfate elution can be an indicator of the dissolution of sulfur-bearing minerals in mine soils. The greatest reduction was observed for Pb and Cu while the lowest was for Cd (2–19%) and Zn (6–51%), consistent with the batch data. Both the reduced elution at slow seepage and concentration drop after flow interruption support the time-limited propensity. In column segments, the sorptive elements (Cu, Pb, and As) were dominantly found in the inlet while less sorptive ones (Zn and Cd) in the outlet. Both batch and column data suggest that the element leaching with mine leachate movement can be greatly attenuated by the interactions with the surrounding downgradient soil during the seepage process.

Role of trivalent bismuth ion substitution at Dy site on the physical properties of DyMnO3

Polycrystalline compounds of Dy1−xBixMnO3 (x = 0 & 0.1) synthesized by ceramic method were characterized by X-ray diffraction technique and their vibrational, transport and magnetic properties studied. Refinement of powder X-ray diffraction data showed that both materials exhibit orthorhombic structure with Pnma space group. Although Bismuth substitution retains the crystal structure, bond angles and bond lengths within MnO6 octahedra are altered as compared to the pristine compound, DyMnO3. While bond angle between manganese ions along the b-axis reduces slightly (1°), axial bond angle increased by ∼3° in the substituted compound. Raman bands arising from the atomic vibrations of rare earth dysprosium and oxygen ions have been identified from room temperature Raman spectra. For 10 at.% substitution of Bi3+, these modes are hardened. Transport measurement studies indicated that the materials are semiconducting in nature with small polaron hopping type of conduction. Hopping energy is decreased to 98.52 meV for Bi3+ substituted DyMnO3 (Dy0.9Bi0.1MnO3) from 103.85 meV for DyMnO3. Temperature dependence of dc magnetization studies revealed anomalies around 39 K, 12 K and 3.62 K corresponding to antiferromagnetic ordering involving Mn3+ and Dy3+ ions respectively. Temperature and frequency variation of ac susceptibility data corroborated the dc magnetization results. In both compounds, magnetization versus applied magnetic field curves measured at several temperatures from room temperature down to 10 K showed linear behavior revealing paramagnetic nature. This behavior indicates the absence of magnetic correlations which is in accordance with MT data. On the other hand, hysteresis loops were observed in M-H data registered ∼2 K with coercive fields of 1520 Oe and 1365 Oe for DMO and DBMO respectively. However, magnetization does not saturate even at 7 × 104 Oe field. The origin for the ferromagnetic coupling could be ascribed to the correlations between Dy3+ and Mn3+ ions through apical oxygen ions in the unit cell favoring superexchange interactions.

Structural and micro-Raman studies of DyMnO3 with potassium substitution at the Dy site

We synthesize a new series of compounds, Dy1−xKxMnO3 (x = 0.1, 0.2 & 0.3) and report the structural and spectroscopic properties of the new compounds in comparison to DyMnO3.

Specific-heat study on successive magnetic transitions in α-Dy2S3 single crystals under magnetic fields

Specific-heat measurements in magnetic fields have been performed on α-Dy2S3 single crystals and have shown successive magnetic transitions at $$T_{N_1 } = 11.4 K$$ and $$T_{N_2 } = 6.4 K$$ . The specific heat in no magnetic field exhibits sharp peaks at both $$T_{N_1 }$$ and $$T_{N_2 }$$ . The change in the magnetic entropy across each transition is estimated as Rln2/2 per mol-Dy, which suggests magnetic moments on only one Dy site between two crystallographically inequivalent Dy sites order at each transition temperature. When the magnetic field is applied along the b-axis of the orthorhombic system, the two peaks of the specific heat shift toward lower temperatures. On the other hand, a magnetic field perpendicular to the b-axis shifts the peaks toward higher temperatures. The $$T_{N_1 }$$ shifts to 9.6 K (H ‖ b) and 12.5 K (H ⊥ b) under a magnetic field of 2 T. The $$T_{N_2 }$$ peak broadens gradually with increasing magnetic field for each direction; consequently, the peak is obscure under a field of 2 T.

Two Bulky-Decorated Triangular Dysprosium Aggregates Conserving Vortex-Spin Structure

The self-assembly of dysprosium(III) with the tailored chemical modification of the vanillin group affords two decorated Dy(3) compounds, namely, [Dy(3)(μ(3)-OH)(2)(Hpovh(-))(3)(NO(3))(3)(CH(3)OH)(2)H(2)O]·NO(3)·3CH(3)OH·2H(2)O (2) and [Dy(3)(μ(3)-OH)(2)(H(2)vovh(-))(3)Cl(2)(CH(3)OH)(H(2)O)(3)][Dy(3)(μ(3)-OH)(2)(H(2)vovh(-))(3)Cl(2)(H(2)O)(4)]·Cl(4)·2CH(3)OH·2CH(3)CN·7H(2)O (3), where H(2)povh = N-(pyridylmethylene)-o-vanilloylhydrazone and H(3)vovh = N-vanillidene-o-vanilloylhydrazone. Of particular interest is that those two title Dy(3) compounds maintain the peculiar vortex-spin structure of the ground nonmagnetic doublet. Complex 2 displays frequency-dependent slow magnetic relaxation, while 3 still inherits the single-molecule-magnet behavior as the parent Dy(3) prototype. The dissimilar dynamic magnetic behavior originates from the structural differences in light of the coordination environment of Dy(III) ions, which influence the local tensor of anisotropy and crystal-field splitting on each Dy site.

A series of 1D Dy(iii) compound showing slow magnetic relaxation: synthesis, structure, and magnetic studies

In this work, we present the synthesis, structure, and magnetic studies of three 1D homo-spin Dy(III) compounds in detail. For 1, one crystallography-independent Dy(III) site is contained and the coordination surrounding is a distorted square-antiprism geometry. Within 2, four crystallography-independent Dy(III) sites with largely distorted square-antiprism geometry are observed. As for 3, two crystallography-independent Dy(III) sites showing bicapped triangular-prism geometry are involved. The magnetic studies suggest weak ferromagnetic interactions for 1 and weak antiferromagnetic interactions for 2 and 3. Their dynamic magnetic properties are investigated by means of alternating current (ac) susceptibility measurement, revealing their slow magnetic relaxation. Moreover, a field-dependent ac signal is observed in 1, when by applying a static dc = 1000 Oe field, strong frequency-dependent ac signals and the peak of out-of-phase (χ'') can be clearly found. Ultimately, by fitting the Arrhenius law the energy barrier and relaxation time are estimated.

Ferroelectricity generated by spin-orbit and spin-lattice couplings in multiferroic DyMnO3

While the ferroelectricity in type-II multiferroic rare-earth manganites is believed to be generated by the inverse Dzyaloshinskii-Moriya (DM) interaction (spin-orbit coupling) associated with the Mn spiral spin order, recent results revealed the strong spin-lattice coupling arising from the Dy-Mn spin interaction in DyMnO3, which may also be an ingredient contributing to the ferroelectricity. In this work, we summarize our recent experiments on this issue by performing a series of rare-earth site nonmagnetic Y and magnetic Ho substitutions at Dy site for DyMnO3. It is demonstrated that the Dy-Mn spin interaction contributes to the ferroelectric polarization through the symmetric exchange striction mechanism (spin-lattice coupling). A coexistence of the spin-orbit coupling and spin-lattice coupling in one compound is confirmed. At the same time, the independent Dy antiferromagnetic spin order at low temperature can be effectively suppressed by the substitutions, beneficial to the polarization enhancement.

Modulating Magnetic Dynamics of Three Dy2 Complexes through Keto–Enol Tautomerism of the o-Vanillin Picolinoylhydrazone Ligand

Complexation of dysprosium(III) with the heterodonor chelating ligand o-vanillin picolinoylhydrazone (H(2)ovph) in the presence of different bases affords three new dinuclear dysprosium(III) coordination compounds, namely, [Dy(2)(ovph)(2)(NO(3))(2)(H(2)O)(2)]·2H(2)O (1), [Dy(2)(Hovph)(ovph)(NO(3))(2)(H(2)O)(4)]·NO(3)·2CH(3)OH·3H(2)O (2), and Na[Dy(2)(Hovph)(2)(μ(2)-OH)(OH)(H(2)O)(5)]·3Cl·3H(2)O (3), where the aroylhydrazone ligand adopts different coordination modes in respective structures depending on the reaction conditions, as revealed by single-crystal X-ray analyses to be due to their tautomeric maneuver. The magnetic properties of 1-3 are drastically distinct. Compounds 1 and 2 show single-molecule-magnet behavior, while no out-of-phase alternating-current signal is noticed for 3. The structural differences induced by the different coordinate fashions of the ligand may influence the strength of the local crystal field, the magnetic interactions between metal centers, and the local tensor of anisotropy on each Dy site and their relative orientations, therefore generating dissimilar dynamic magnetic behavior.

Multiferroic phase diagram of Y partially substituted Dy1−xYxMnO3

The effect of nonmagnetic Y partial substitution at the Dy site in Dy1−xYxMnO3 up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (TDy) and ferroelectric ordering point (TFE) but enhances the Mn-spin ordering point (TN). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn.

Crystal growth of spin-ice pyrochlores by the floating-zone method

Single crystals of RE2Ti2O7 (RE=Y, Tb, Dy and Ho) have been grown by the floating-zone technique in an image furnace in a controlled atmosphere. The effect of annealing the crystals in different atmospheres was studied and found to be very important. Small amounts of Y were doped on the Dy site to study its effect on the spin-ice behaviour. Results for the structural parameters obtained by X-ray diffraction and magnetic properties of the crystals are reported.