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Single-molecule magnets could prove useful in miniaturizing a wide variety of devices. However, their application has been severely hindered by the need to cool them to extremely low temperature using liquid helium. Guo et al. now report a dysprosium compound that manifests magnetic hysteresis at temperatures up to 80 kelvin. The principles applied to tuning the ligands in this complex could point the way toward future architectures with even higher temperature performance. Science , this issue p. 1400 Ligand tuning raises the upper temperature for hysteresis in a single-molecule magnet just above nitrogen’s boiling point. Single-molecule magnets (SMMs) containing only one metal center may represent the lower size limit for molecule-based magnetic information storage materials. Their current drawback is that all SMMs require liquid-helium cooling to show magnetic memory effects. We now report a chemical strategy to access the dysprosium metallocene cation [(Cp i Pr5 )Dy(Cp*)] + (Cp i Pr5 , penta-iso-propylcyclopentadienyl; Cp *, pentamethylcyclopentadienyl), which displays magnetic hysteresis above liquid-nitrogen temperatures. An effective energy barrier to reversal of the magnetization of U eff = 1541 wave number is also measured. The magnetic blocking temperature of T B = 80 kelvin for this cation overcomes an essential barrier toward the development of nanomagnet devices that function at practical temperatures.

Most commercially available phosphors are made from appropriately doped polycrystalline materials while the activation methods have often been examined, the impact of fuels on the host preparation and its effect on the final performance of the products has received less focus. This paper explores the use of various fuels in the synthesis of Dy-doped CaAl 2 O 4 phosphors. Dysprosium-doped monoclinic CaAl 2 O 4 phosphors were obtained at low temperatures (500 °C) by the process of combustion of the corresponding metal nitrate–fuel mixtures, over a period of 5 min. In this paper, attention has been paid to the influence of fuels on the luminescence properties of the phosphor sample which is prepared by solution combustion method. Dy-activated CaAl 2 O 4 phosphor was synthesized by combustion technique using hydrazine, carbohydrazide, and urea as fuels. XRD analysis reveals that introducing a small quantity of rare earth ions into the raw materials did not alter the crystal structure of CaAl 2 O 4 . XRD result confirms the formation of the sample. Photoluminescence (PL) emission spectrum showed characteristic emission of Dy doped in the CaAl 2 O 4 samples. The highest photoluminescence intensity was observed at a 0.02 mol% concentration of Dy. The PL spectrum exhibits wide peaks near 488 and 573 nm when excited at 347 nm. Mechanoluminescence (ML) and Thermoluminescence (TL) properties of the material have been emphasized. Various ML and TL curves have been recorded to assess which of the fuels yields the most efficient CaAl 2 O 4 : Dy compound. The prepared sample may be useful in TL dosimetry. In the present investigation it is found that urea is a better fuel for preparing CaAl 2 O 4 : Dy phosphors and enhances the ML and TL intensity of the sample. Graphical abstract PL emission spectra of CaAl2O4: Dy phosphors synthesized by urea, carbohydrazide and hydrazine, where urea provides the highest PL intensity, making it an optimal choice for enhancing optical performance.

During the liquid metal extraction reaction between a Nd-Dy-Fe-B magnet and liquid Mg, Nd rapidly diffuses out of the magnet, whereas Dy is not extracted due to the reaction with the matrix and the formation of Dy2Fe17 phase. In addition, theDy2O3 phase exists at the grain boundaries. Until now, only the effect of the Dy2O3 phase on the extraction of Dy has been reported. In this study, the effect of the Dy2Fe17 phase on the extraction of Dy from the Nd-Dy-Fe-B magnet was investigated in liquid Mg. The formation of the Dy2Fe17 phase during the reaction between Mg and matrix (RE2Fe14B) was first examined using a thermodynamical approach and confirmed by microstructural analysis. It was observed that Dy extraction was dominated by Dy2Fe17 phase decomposition from 3 h to 24 h, followed by Dy2O3 phase dominant reaction with Mg. Comparing the activities of the Dy2Fe17 phase and the Dy2O3 phase, the reaction of Dy2Fe17 is dominant, as compared to the Dy2O3 phase. Finally, at 48 h, the high Dy extraction percentage of 93% was achieved. As a result, in was concluded that the Dy2Fe17 phase acts as an obstacle in the extraction of Dy. In the future, if research to control the Dy2Fe17 phase proceeds, it will be of great importance to advance the recycling of Dy.

Synthetic garnets are a group of oxide materials that play a vital role in the development of solid state lasers, magnetic and optic-electronic devices. The analysis on the solubility of rare-earth elements in the well-crystallized system has led to the discovery of peculiar oxide materials with multifunctional properties. By following the above importance, Aluminium ion (Al3+) substituted Dysprosium Iron Garnet compounds with the chemical formula of Dy3Fe5−xAlxO12 (x = 0–0.5) have been synthesized by the solid state reaction method and the effect of substitution of non-magnetic ions into the magnetic sub-lattices have been analyzed. The Rietveld refinement of powder x-ray diffraction patterns confirms that the pure Dy3Fe5O12 compound crystallizes with cubic (Space group: Ia3d) superstructure whereas all the Al3+ substituted samples exhibit the coexistence of cubic (Ia3d) and trigonal Fe2O3 (R3c) phases. The energy gap values of the prepared compounds is found to be around 1.6 eV which reveals the semiconducting nature and the decreasing trend of band gap values may be due to the growth factor of crystallites, structural disorder and distortion introduced into the crystal lattice. From the Micro-Raman analysis, it is found that the substituted Al3+ ions starts filling into both tetrahedral and octahedral positions and the assignments of vibrational modes observed from Raman spectra confirm the incorporation of Al3+ ions into the Dy3Fe5O12 garnet structure. From the magnetization analysis, it is found that the response of super-exchange interaction between Fe3+ ions in the a and d sites of Dy3Fe5O12 compound leads to net magnetic moment and the substitution of Al3+ ions preferably replaces Fe3+ ions in d sites and suggests the decrease in net magnetization values. From the photoluminescence studies, it is noticed that the luminescence behavior of Al3+ ions substituted Dy3Fe5−xAlxO12 compounds are due to the superposition of a broad emission band and reveals the variation in concentration of Al3+ ions in the prepared compounds. An interesting point to note is that, a well saturated “soft” ferroelectric hysteresis loop is obtained in both pure and Al3+ substituted Dy3Fe5−xAlxO12 compounds, and the observed electric hysteresis loops are found to be influenced by the factors such as capacitance nature, resistivity effects and leakage current of the compounds. Hence, the study on effect of trivalent non-magnetic ion substitution in a hard magnetic Dy3Fe5O12 system leads to interesting intrinsic magnetic and ferroelectric properties and found suitability for the fabrication of energy storage and optoelectronic devices.

The interlayer interactions in multilayer systems with a non-magnetic semimetallic interlayer are great of interest. The magnetic and structural properties of the Dy x Co 1-x /Bi/Py systems (17 <  x  < 26 at.%) have been studied. The temperature dependences of magnetization in the range 4.2–300 K were measured for the first time. The influence of the bismuth interlayer thickness on the exchange interaction between the DyCo and Py layers was found as well as the critical value of its thickness. The obtained atypical value of the period of exchange bias oscillations was explained by the formation of bismuth compounds with dysprosium–pnictogenides at bismuth thicknesses below the critical value. The interface was investigated by spectral ellipsometry in the range 2–5 eV. The information on the structure of the surface obtained by atomic force microscopy was used to create a multilayer model for fitting experimental ellipsometric data. Analysis of the optical properties showed that pnictogenide Dy 3 Bi 2 is formed at the interface, which affects the general magnetic state of the samples studied.

Production of high energy permanent magnets (HEPM) on the basis of rare-earth metals is one of leading knowledge intensive branches of world industry. Raw materials for production of magnets are magnetic alloys. In order to increase magnetic features scientists implement the additives of certain metals and their compounds, such as dysprosium and terbium additives in substantial amounts – up to 7-8 %.Within the framework of a ladle fluoride technology of HEPM manufacturing on the basis of a system Nd-Fe-B, developed by authors, scientists implement the additives of dysprosium and terbium fluoride, by virtue where of there was conducted a research on fluoration kinetics of corresponding oxides by elemental fluorine. The present article quotes results of such research and defines main kinetic parameters of examined processes – diffusion coefficient, kinetic constant and activation energy. Aiming to cost reduction of fluoride manufacture ammonium fluoride was used as a fluorinating agent by the example of fluoration of neodymium oxide.

The linear thermal expansion coefficient α(T) of two high-Tc superconductors, YBa2Cu3O7 and DyBa2Cu3O7 has been revisited in the 4.5-80K temperature range. The X-ray diffraction analysis and microstructural characterization using scanning electron microscopy confirm an orthorhombic single phase with an average of the grain size of about 20 μm for both polycrystalline samples. In the case of the Dy compound, a small magnetic excess superimposed to the high phonon contribution is observed in the T3 term, whereas no anomaly is detected below 40K. The deduced magnetic contribution αm(T) which increases monotonically with rising temperature is attributed to the CF interactions induced by the 4f electric quadrupole moment of the Dy Kramers ions. A discussion and a comparison with respect to the previous experimental and theoretical works are presented.

The unique electronic and magnetic properties of Lanthanides molecular complexes place them at the forefront of the race towards high-temperature single-ion magnets and magnetic quantum bits. The design of compounds of this class has so far been almost exclusively driven by static crystal field considerations, with emphasis on increasing the magnetic anisotropy barrier. This guideline has now reached its maximum potential and new progress can only come from a deeper understanding of spin-phonon relaxation mechanisms. In this work we compute relaxation times fully ab initio and unveil the nature of all spin-phonon relaxation mechanisms, namely Orbach and Raman pathways, in a prototypical Dy single-ion magnet. Computational predictions are in agreement with the experimental determination of spin relaxation time and crystal field anisotropy, and show that Raman relaxation, dominating at low temperature, is triggered by low-energy phonons and little affected by further engineering of crystal field axiality. A comprehensive analysis of spin-phonon coupling mechanism reveals that molecular vibrations beyond the ion's first coordination shell can also assume a prominent role in spin relaxation through an electrostatic polarization effect. Therefore, this work shows the way forward in the field by delivering a novel and complete set of chemically-sound design rules tackling every aspect of spin relaxation at any temperature

We have investigated for the first time the magnetic behaviour of an intermetallic compound, Dy4RhAl, crystallizing in Gd4RhIn type cubic structure containing 3 sites for rare-earth (R), by several bulk measurements down to 1.8 K. This work is motivated by the fact that the isostructural Dy compound in the R4PtAl family surprisingly orders ferromagnetically unlike other members of this series, which order antiferromagnetically. The results reveal that the title compound undergoes antiferromagnetic order at about 18 K, similar to other heavy R members of R4RhAl family, unlike its Pt counterpart, indicating a subtle difference in the role of conduction electrons to decide magnetism of these compounds. Besides, spin-glass features coexisting with antiferromagnetic order could be observed, which could mean cluster antiferromagnetism. The electrical resistivity and magnetoresistance behaviours in the magnetically ordered state are typical of magnetic materials exhibiting antiferromagnetic gap. Features attributable to spin-reorientation as a function of temperature and magnetic field can be seen in the magnetization data.

Magnetic hysteresis is a direct manifestation of non-equilibrium physics that has to be understood if a system shall be used for information storage and processing. The dilanthanide endofullerene Tb2ScN@C80 is shown to be a single-molecule magnet with a remanence time in the order of 100 s at 400 mK. Three different temperature dependent relaxation barriers are discerned. The lowest 1 K barrier is assigned to intermolecular interaction. The 10 K barrier to intramolecular exchange and dipolar coupling and the 50 K barrier to molecular vibrations as it was observed for Dy2ScN@C80. The four orders of magnitude difference in the prefactor between the Tb and the Dy compound in the decay process across the 10 K barrier is assigned to the electron number in the 4f shells that evidences lack of Kramers protection in Tb3+. The sub-Kelvin hysteresis follows changes in the magnetisation at adiabatic and non-adiabatic level crossings of the four possible Tb2 ground state configurations as is inferred from a zero temperature hysteresis model.