Type Of Rare-earth Ion Research Articles

Enhanced solvent extraction of rare earth elements in ultra-high phase ratio with pore-throat microchannels

To enrich and recover low-concentration (101–102 ppm) rare earth elements from ores and industrial wastes, high phase-ratio solvent extraction is favored. However, high phase-ratio solvent extraction is limited by low mass transfer efficiency in the continuous phase due to the insufficient contact between large volume continuous phase and sparse droplets. To realize efficient solvent extraction of rare earth ions from low concentrations (100 ppm) aqueous phase to oil phase with high phase ratio, we introduce a type of microchannel with sequential pore-throat geometry. This sequential pore-throat geometry creates capillary barriers and effectively retains dispersed droplets, leading to a reduction of apparent water–oil volume ratio and thereby major mass transfer enhancement in the continuous phase. We experimentally highlight its advantage over classic uniform microchannel for solvent extraction of rare earth ions under high phase ratios: in a double pore-throat microchannel, extraction equilibrium can be reached within 30 s under high phase ratios of 50–250; for an extreme phase ratio of 500:1, extraction efficiency can achieve 77 % within a quadruple pore-throat channel, while that within a uniform microchannel is only below 40 %. The superiority of sequential pore-throat microchannel for extraction at a high phase ratio is reproduced using different types of rare earth ions. We thus conclude that sequential pore-throat geometry can drastically promote the performance of microfluidic-based solvent extraction at extreme phase ratios, for rare earth enrichment and potentially for other relevant applications.

A Study of R2T14B (R = Y, Nd, Gd, Ho, T = Fe, Co) Hard Magnetic Materials via Magnetometry and Atomic Force Microscopy

Magnetometry and atomic force microscopy (AFM) were used to study the magnetic and structural properties of the R–Fe–B-type (R = Y, Nd, Gd, Ho) alloys. The alloys were synthesized by means of induction melting. The nanocrystalline state of the R–Fe–B-type alloys was reached, mainly, by melt spinning (MS). A multistage treatment of R–Fe–B-type alloys, which included severe plastic deformation of melt-quenched ribbons and subsequent heat treatment, was also used. The surface morphology of samples was studied in detail to interpret the observed magnetic hysteresis loops of the samples. It was found that the type of rare earth ion and treatment methods had the most important influence on the microstructure and magnetic properties.

Er:YAG/Yb:YAG nanopowders‐derived Er/Yb co‐doped yttrium aluminosilicate (YAS) fibers fabricated by UV‐curable nanocomposites for 1.5‐µm single‐frequency fiber lasers

AbstractThe rare‐earth (RE)‐doped yttrium aluminosilicate (YAS) glass fibers have demonstrated their unique advantages in single‐frequency lasers due to their high solubility of RE ions and high gain per unit length. However, the RE‐doped YAS fiber is usually fabricated by RE:YAG crystal or ceramic rods and melting‐in‐tube method, which depend heavily on RE:YAG crystal or ceramic rods and, thus, cannot adjust the fiber compositions effectively; there is little research on the multiple RE ions co‐doped YAS fiber deriving from RE:YAG crystal or ceramic rods. In present work, we developed a novel method to fabricate Er/Yb co‐doped YAS fibers efficiently. The Er:YAG and Yb:YAG nanopowders were fabricated by the coprecipitation method, and then the nanopowders were dispersed into liquid organic resin to form a novel UV‐curable nanocomposite, after curing, debinding, purifying, and drawing process, an Er/Yb co‐doped YAS fibers was fabricated, the absorption coefficients of the fiber was measured to be 17 dB/cm at 976 nm (2F7/2ground level to2F5/2level of Yb and4I15/2ground level to4I11/2level of Er) and 3.2 dB/cm at 1530 nm (4I15/2ground level to the high states of4I13/2of Er). A 1.5‐µm single‐frequency laser was constructed with the 2‐cm Er/Yb co‐doped YAS fiber. The longitudinal mode spacing was calculated to be 2.2 GHz with an effective cavity length of 4.5 cm, and the spectral signal‐to‐noise ratio was higher than 60 dB. To the best of our knowledge, it is the first time that Er/Yb co‐doped YAS fibers are fabricated using the UV‐curable nanocomposites. It indicates that this proposed technology is critical for the fabrication of various types of RE ions co‐doped YAS fibers and their applications in single‐frequency fiber lasers.

Characterization of interactive up-conversion luminescence mechanisms in Tm3+/Ho3+/Yb3+ doped yttria stabilized zirconia single crystals

Yttria stabilized zirconia (YSZ) single crystals doped with Tm2O3, Ho2O3, and Yb2O3 were prepared by the optical floating zone method in order to investigate the effects of varying the Tm3+, Ho3+, Yb3+ contents on the luminescence properties. All samples were shown by powder X-ray diffractometry (XRD) to be in the cubic phase at room temperature with good crystallinity, and the optical bandwidth of about 4.63 eV indicates their suitability for the development of luminescence products. The blue emission peaks from Tm3+ following excitation with a 980 nm (1.33 eV) laser increased with Tm3+ content reached a maximum in the crystal with 0.30 mol% Tm2O3, and then decreased with higher Tm3+ concentrations as a result of quenching caused by electric dipole interactions. The ratio of the integral intensities of the green emission peaks at 2.42 eV (539 nm) and 2.36 eV (552 nm) indicate that the probability of the non-radiative transition from the 5F4 level of Ho3+ to the 5S2 level decreases with increasing Tm3+ concentration. This research also demonstrates that there was competition between Ho3+ and Tm3+ for the transfer of energy from excited Yb3+, and that there was also direct transfer of energy from Ho3+ to Tm3+. Thus, in YSZ doped with a combination of rare earth ions, the luminescence properties are determined by a combination of energy transfer processes between the different types of rare earth ions, as well as those for the individual ions, and thus presents an opportunity for fine tuning emissions from such crystals to produce a new generation of materials with intense luminescence properties.

Synthesis and Characterization of CaAl2O4: Dy3+ and CaAl2O4: Sm3+ Phosphor Powders

Calcium aluminate, CaAl2O4 is efficient and well known host material for inorganic phosphors. Although this host structure is mostly doped with Eu2+, different types of rare earth ions have also been studied. In this study, attention was drawn to CaAl2O4 type phosphors doped with Dy3+ and Sm3+ at different concentrations. Ca1-xAl2O4: Dy3+x (x= 0.008, 0.012, 0.02, 0.03) and Ca1-yAl2O4: Sm3+y (y= 0.008, 0.012, 0.02, 0.03) phosphors were synthesized as powder samples through the solid-state reaction method. After heat treatments, monoclinic CaAl2O4 structure was confirmed for all rare earth doped samples by the XRD analysis. PL characteristics of samples depend on activator ion. The PL emission spectra of Dy3+ doped powder samples show two strong bands at 484 nm and 577 nm which are attributed to a typical 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions. Sm3+ activated phosphors have the emission peaks at 565 nm, 604 nm, 649 nm, and 712 nm which are assigned to Sm3+ transitions: 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2, 4G5/2 → 6H11/2, respectively. The Commission International De IEclairage (CIE) 1976 chromaticity coordinates were evaluated from the emission spectra in two different rare earth ion doped phosphors, the values (uꞌ = 0.21805, vꞌ = 0.52537) and (uꞌ = 0.36078, vꞌ = 0.54567) were colors of yellow-orange and brick red, respectively. Consequently, synthesized Ca1-xAl2O4: Dy3+x (x= 0.008) and Ca1-xAl2O4: Sm3+y (y= 0.008) phosphors emitting in different color regions can be useful for LED’s and display applications.

Synthesis and photoluminescence properties of novel LaGa0.5Sb1.5O6: Eu3+, Dy3+, Tb3+ and BiGeSbO6: Eu3+, Dy3+, Tb3+ phosphors

In this work, novel phosphors LaGa0.5Sb1.5O6 and BiGeSbO6 doped with Eu3+, Tb3+, and Dy3+ were synthesized, and the luminescent properties were studied. The impact of the host type on the emission properties was demonstrated for compositions singly doped with Eu3+ and Dy3+ ions. For the La1−xEuxGa0.5Sb1.5O6 and Bi1−xEuxGeSbO6 (x = 0.05–0.5) solid solutions, there were evident differences in the luminescence intensity ratio of the bands caused by the 5D0→7F1 and 5D0→7F2 transitions of Eu3+ that may have resulted from a different rare earth (RE) ion coordination environment. The spectra of all the bismuth-containing solid solutions were characterized by the appearance of an additional band related to the intrinsic luminescence of the bismuth-containing host. The intensity ratio of this band and the RE ion emission lines for dysprosium-containing compounds was much higher than that for compositions doped with praseodymium and europium. Co-doping with Eu3+, Dy3+, and Tb3+ ions led to a shift in the emission colour to orange (when doped with two types of RE ions) and yellow-orange (when doped with three types of RE ions).

Effective resistance to dendrite growth of NASICON solid electrolyte with lower electronic conductivity

The interface resistance, relative density and electronic conductivity of ceramic electrolytes show great influences on the formation of dendrites, which is the dominant challenge of solid-state lithium/sodium batteries in the practical application. In this work, NASICON electrolytes (Na3Zr2Si2PO12) with enhanced ionic conductivity, improved relative density and lowered electronic conductivity were demonstrated through doping lanthanide ions (Pr3+, Eu3+ and Lu3+). The influences of lanthanide ions doping on the crystalline structure, density, ionic/electronic conductivity and the application performances especially for the resistance to dendrite growth were investigated in detail. The ionic conductivity and relative density were promoted whereas the electronic conductivity was reduced obviously for the Na3Zr2Si2PO12 electrolyte with the presence of lanthanide ions with low electronegativity, resulting in the promoted resistance to dendrite growth. Among the three types of rare earth ions, highest critical current density (CCD) of 0.9 mA/cm2 at RT was recorded for the Pr3+ doped Na3Zr2Si2PO12 electrolyte due to its compact microstructure and low electronic conductivity, owing to the substitution of Zr4+ ions by the Pr3+ ions with smallest electronegativity and largest ion radius. The presented results proved that the doping of appropriate rare earth ions can significantly decrease the electronic conductivity, resulting in the resistance to sodium dendrite for NASICON solid electrolyte.

Phonon Spectroscopy of the Schottky-Like Low-Energy Paramagnetic Excitations in Garnet Solid Solution Crystals

The interaction of weakly nonequilibrium phonons with the low-energy paramagnetic excitations of the rare-earth ions of the yttrium series in rare-earth garnet solid solutions is studied at liquid-helium temperatures. The interaction of nonequilibrium phonons with the low-energy excitations of Ho3+ and Tb3+, which are caused by local electric fields in a crystal lattice, is experimentally investigated. In the row of Kraemrs ions (where the nature of low-energy excitations is caused by the splitting of the ground level of a paramagnetic ion due to the local magnetic fields of neighboring ions), interaction in the nonequilibrium phonon–low-energy excitation system is only detected in the Er-containing solid solutions and is absent in the structures containing Gd3+, Dy3+, and Yb3+ rare-earth ions. In the two-level system model, the efficiency of interaction and the transport characteristics of thermal phonons are shown to depend on the type of rare-earth ion, the energy and spectral features of two-level systems, the moments of electrons in the 4f shell, and spin–lattice relaxation.

Structure of nanocrystalline Nd0.5R0.5FeO3 (R=La, Pr, and Sm) intercorrelated with optical, magnetic and thermal properties

Polycrystalline samples of Nd0.5R0.5FeO3 (R = La, Pr and Sm) synthesized by sol-gel combustion method have been investigated for their structural, optical, thermal and magnetic properties. X-ray diffraction in combination with Fourier transform infrared (FTIR) spectra confirm the single-phase orthorhombic structure with Pbnm space group of all the samples. Rietveld refinement employed to determine the bond lengths (Fe–O, R–O) and bond angles (Fe–O–Fe) show a decrease in the bond angle with Sm doping. Transmission electron microscopy (TEM) micrographs reveal the nano-size particles and selected area electron diffraction (SAED) patterns indicate good crystallinity with a uniform distribution of particles throughout the samples. Raman spectra clearly indicate the compressive strain in the Sm doped sample that has been correlated with the structural parameters obtained from Rietveld refinement. The shift in wavenumber is the main cause of change in bond length (Fe–O) and tilt of octahedra due to rare earth ions. The optical bandgap is determined using Tauc's relation from the diffuse reflectance spectra. The variation of specific heat has been investigated with temperature in a broad temperature range. The endothermic peak in specific heat has been correlated with magnetic order. The value of Néel temperature increases in the case of La-doped sample and reduces for the Pr doping. However, the decrease of specific heat in Sm doped sample around 300 °C may be attributed due to the spin reorientation. Magnetic studies at room temperature reveal antiferromagnetic behavior with weak ferromagnetic component due to the canted ordering of Fe3+ spins. Magnetic properties are strongly dependent on the type of rare earth ion as the maximum magnetization (Mm) is enhanced from 0.259 to 0.434 emu/g with the doping of rare earth ions (La, Pr and Sm). The increase in magnetization has been correlated with increased distortion which is evident from the decrease in the bond angle. Exchange bias (EB) effect is observed for all samples as single-phase orthorhombic structure is composed of antiferromagnetic (AFM) and ferromagnetic (FM) phases.

Structural, magnetic, dielectric and high frequency response of synthesized rare earth doped bismuth nano garnets (BIG)

Abstract Rare earth doped bismuth (Bi) iron garnets (BIG) having composition Bi3−xRxFe5O12 for x = 1.5 (here R stands for rare earth elements like Y, Gd, Pr, Ho and Yb) have been studied in this work. The samples were prepared using sol-gel method. X-Ray diffraction (XRD), Scanning electron microscope (SEM), Fourier transform infrared spectroscope (FTIR), Vibrating sample magnetometer (VSM) and Vector network analyzer (VNA) were employed on the samples to evaluate the properties of the doped Bi nanogarnets. Single-phase garnet structure was confirmed through XRD and the crystallite sizes were found to be 66–73 nm, depending upon the type of rare earth ions. SEM images helped to observe the morphology and measurement of grain size of the doped Bi nanogarnets. Vibrational bands showed the presence of garnet phase and were confirmed through FTIR analysis. Detailed dynamic magnetic and dielectric properties were measured using VNA from 1 to 6 GHz. Real and imaginary part of the permittivity, permeability, dielectric and magnetic losses, ac conductivity, electric modulus and Q factor were calculated for the rare earth doped Bi nanoferrites. Gd doped Bi nanoferrites showed higher permittivity values whereas Pr doped show higher ac conductivity as compared to other samples. Yb doped Bi nanoferrites have Q factor values at 4.8 GHz. Static magnetic properties of the doped Bi nanogarnets were investigated using magnetic loops. Magnetic remanence (Mr) Saturation magnetization (Ms) and coercivity (Hc), Bohr magneton, anisotropy constant and initial permeability were also calculated. The dielectric and magnetic studies of the rare earth doped Bi nanogarnets suggested the applications of these rare earths doped nanogarnets for microwave devices and high frequency applications in GHz regime.

TiO2/Sepiolite nanocomposites doped with rare earth ions: Preparation, characterization and visible light photocatalytic activity

Abstract Several rare earth (RE)-doped TiO2/Sepiolite (RE-TiO2/Sep) photocatalysts were prepared via microwave-hydrothermal treatment using six different types of RE ions: La, Ce, Pr, Nd, Eu or Gd. The obtained nanocomposites were characterized by using BET, XPS, PL and UV-vis techniques. The results revealed that the structures and chemical properties of the nanocomposites were significantly dependent on the radius of the RE3+. Since the radius of RE3+ is much larger than that of Ti4+, Ti4+ could replace RE3+ in the lattice of RE2O3 in the form of Ti3+ state and create a charge imbalance due to their smaller ionic radii. Correspondingly, for charge balance, more OH− will be adsorbed. The unoccupied 4f level of RE acts as a scavenger for photogenerated electrons, while surface adsorbed OH− acts as a hole trap, separating the photogenerated electron-hole pairs effectively. Eu-TiO2/Sep nanocomposite showed the best photocatalytic activity among all the RE-doped nanocomposites studied. The enhanced visible-light activity is mainly attributed to the enhanced separation of photoinduced carriers, low band gap energy, strong visible light absorption, high adsorption capacity and uniform distribution of titania nanoparticles on sepiolite as support.

Effect of a Rare-Earth Ion on the Structural Instability in RFe3(BO3)4 Crystals

The dynamics of the crystal lattice of RFe3(BO3)4 (R = Pr, Nd, Sm, Gd, Tb, Dy, and Ho) compounds in the high-symmetry R32 phase has been calculated. Significant changes in spectra of compounds with various rare-earth ions have been obtained only near the edge Λ point of the Brillouin zone (qΛ = 1/3(−2b1 + b2 + b3, where b1, b2, and b3 are the reciprocal lattice vectors) for acoustic oscillation branches. A decrease in the frequency of an acoustic mode at the point Λ has been revealed in all studied compounds. This frequency depends on the type of rare-earth ion and decreases from a compound with Pr to a compound with Ho down to imaginary values. Such a behavior of the frequency of the unstable acoustic mode is in good agreement with experimental data on the dependence of the temperature of the R32 → P3121 structural phase transition on the type of rare-earth ion in ferroborates.

Fabrication and characterization of TiO2/Sepiolite nanocomposites doped with rare earth ions

Several rare earth (RE)-doped TiO2/Sepiolite (RE-TiO2/Sep) photocatalysts were prepared via microwave-hydrothermal treatment using six different types of RE ions: La, Ce, Pr, Nd, Eu or Gd. The obtained nanocomposites were characterized by using XRD, SEM and TEM techniques. The results revealed that the structures of the nanocomposites were significantly dependent on the radius of the RE3+. Since the radius of RE3+ is much larger than that of Ti4+, the doped RE species were not incorporated into the matrix of TiO2 but rather lie in the grain junctions and boundaries of titania. By forming the Ti-O-RE bonds, the crystallite growth of titania can be inhibited owing to the relatively larger radii of RE3+ ions.

Influence of iron substitution by selected rare-earth ions on the properties of NiZn ferrite fillers and PVC magneto-polymer composites

Nickel-zinc ferrites are very important soft magnetic materials from the point of view of diverse technical applications (such as, e.g., various electronic devices and components) for their high magnetic permeability and permittivity, low core loss, high resistivity, high Curie temperature as well as mechanical strength and chemical stability. Due to their good absorbing properties, they can be used as microwave absorbing and shielding materials with the aim of decreasing the environmental pollution caused by non-ionizing microwave radiation. The ferrite material incorporated into the polymer matrix creates qualitatively new magneto-polymer composite material taking benefits from both components. The properties typical for polymers (elasticity, mouldability, etc.) are combined with good high-frequency magnetic parameters, thus allowing to utilize these materials, e.g., in high-frequency applications where especially flexibility of composite materials plays a key role. Small amounts of selected rare-earth (RE) ions, in particular Y3+, La3+, Eu3+ and Gd3+ have been embedded into the nickel-zinc ferrite that has been used as the magnetic filler in magnetic polymer composites with polyvinylchloride (PVC) acting as the polymeric matrix. The effect of various types of rare-earth ions on the structural as well as quasi-static and dynamic (electro)magnetic properties of the ferrite fillers as well as ferrite/PVC composites, in particular the frequency dispersion of the complex permeability, has been studied.

Crystallisation studies of RE2O3[sbnd]Al2O3[sbnd]SiO2 glasses under long heat-treatment conditions

Glasses in the RE2O3Al2O3SiO2 (RE = Y, Nd, Yb, Dy, Ho and Sc) system were prepared using the melt-quench route. Prepared glasses were characterized using differential scanning calorimetry and differential thermal analyses to determine their glass transition temperatures, crystallisation temperatures, softening temperatures and specific heat. In-situ high temperature X-ray powder diffraction was used to study the crystals growth behaviour in these glasses from room temperature up to 1200 °C. Glasses were heat-treated at 1200 °C for 50 h to analyze the crystalline structures. X-ray diffraction studies were carried out to find the distribution of phases in these heat-treated samples. Qualitative and quantitative phase analyses were conducted using scanning electron microscopy combined with energy dispersive analysis. Moreover coefficients of thermal expansion, densities and refractive indices of these glasses were determined. It was found that transitions temperatures and crystalline structure morphology strongly depend on the type of rare-earth ions.

Influence of rare-earth ions on the dielectric response in stillwellite glasses

Experimental spectra of the dielectric response function of glasses with the composition LnBGeO 5 (Ln = La, Pr, Tb, Er, Sm) in the terahertz and infrared ranges are compared. Absorption bands are identified, and their contributions to permittivity are established. The contours of the boson peak and the dependence of the dielectric loss on the type of rareearth ion are determined.

Faraday Rotation Spectra Analysis on TbYbBiIG Crystals in Optical Communication Band

his paper is concerned with the FR spectra analysis on the Bi, Tb and Yb partially substituted iron garnet crystals of Tb3-x-yYbyBixFe5O12. A specific FR (-1617o/cm at 1.55μm), a low FWC (0.009%/nm at 25oC) of Tb0.91Yb1.38Bi0.71Fe5O12 crystals grown from Bi2O3 self-fluxed melts can be used as broadband optical communication components. In order to interpret their FR spectra, a theory based on molecular-orbital levels of Fe3+ in tetrahedral and octahedral sites is used. It is shown that in the case of higher Bi3+ substitution, FR is mainly determined by the contribution of Fe3+ in the octahedral site. Furthermore, two types of rare-earth ions (Tb3+ and Yb3+) moderate the contribution to FR from Fe3+ in octahedral and decahedral sites and eventually have caused that Bi-substituted mixed rare-earth iron garnet has a near-zero Faraday rotation wavelength coefficient (FWC).

Synthesis under ambient pressure and tri-axial magnetic orientation in REBa2Cu4O8 (RE = Y, Sm, Eu, Gd, Dy, Ho, Er)

We report the rare-earth (RE)-dependent magnetization axes of REBa2Cu4O8, which was synthesized by a flux method under ambient pressure, using powder samples tri-axially oriented in a modulated rotating magnetic field of 10T. By optimizing the growth temperature and cooling rate, RE124 crystals were successfully grown for RE=Y, Sm, Eu, Gd, Dy, Ho, and Er. From the X-ray diffraction measurement, the magnetically oriented directions were largely dependent on the type of RE ions of RE124. However, the tri-axial magnetic anisotropies of RE124 could be qualitatively understood in terms of the magnitude relation between the single-ion magnetic anisotropy of RE3+ ions and the magnetic anisotropy generated by the CuO2 plane and Cu–O chain. For the practical use of this magneto-scientific process, the control of magnetization axes and tri-axial magnetic anisotropies through crystallochemical control is indispensable.

Magnetoelectric and magnetoelastic properties of rare-earth ferroborates

The magnetic, electric, magnetoelectric, and magnetoelastic properties of rare-earth ferroborates RFe3(BO3)4 (R=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er) as well as yttrium ferroborate YFe3(BO3)4 have been studied comprehensively. A strong dependence not only of the magnetic but also magnetoelectric properties on the type of rare-earth ion, specifically, on its anisotropy, which determines the magnetic structure and the large contribution to the electric polarization, has been found. This is manifested in the strong temperature dependence of the polarization below the Néel point TN and its specific field dependence, which is determined by the competition between the external and exchange f-d fields. A close correlation has been found between the magnetoelastic properties of ferroborates and the magnetoelastic and magnetic anomalies at magnetic-field induced phase transitions. It is found that in easy-plane ferroborates, together with magnetic-field induced electric polarization spontaneous polarization also arises below the Néel point. The ferroelectric ordering in ferroborates is of extrinsic character, giving rise to strong magnetoelectric coupling below TN. Aside from the antiferromagnetic phase transition, the particulars of the structural phase transition accompanied by anomalies of the dielectric and magnetoelectric properties are examined for the first time. The character of the dielectric anomalies at a structural transition is analyzed for the first time on the basis of Landau’s approach.

Photomagnetic effect in molecular magnets based on nitrosyl complexes of ruthenium and rare-earth ions

The magnetic properties of new bifunctional molecular magnets based on nitrosyl complexes of ruthenium and thiacalix[4]arenes of rare-earth ions (Gd3+, Dy3+) have been investigated. A photoinduced decrease in the magnetization of the molecular magnet with rare-earth ions Gd3+ and the absence of a photomagnetic effect in crystals with rare-earth ions Dy3+ have been revealed at a temperature of 2 K. It has been found that, in the sample containing Dy3+ ions, the magnetization deviates by 6% from the calculated value for noninteracting ions. A comparison of the results obtained for two groups of isostructural samples, which differ only in the type of rare-earth ions, has demonstrated that the observed deviation of the magnetization is caused by the interaction of the orbital moment of the Dy3+ ions with the crystal field.