Rare Earth Intermetallic Compounds Research Articles

The mechanism of magnetization reversal of 2:14:1 high-entropy rare-earth permanent magnets

Rare-earth elements share similar ground-state electronic properties, and their unique lanthanide contraction effect can lower the mixing enthalpy of rare-earth elements in high-entropy materials, which is of paramount importance for the fabrication of low-cost and high-performance high-entropy rare-earth intermetallic compounds. In this paper, the magnetization reversal mechanisms of rapidly quenched ribbons such as Nd<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub> (NdFeB) and the relevant high-entropy rare-earth permanent magnet alloy compounds (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Dy<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub>and (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Tb<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub>were studied by analyzing the magnetization and demagnetization curves, supplemented by Henkel curves and magnetic viscosity coefficient <i>S</i>. Compared to the pure NdFeB sample, the inter-grain exchange coupling in high-entropy rare-earth permanent magnets is significantly enhanced, while the magnetic dipole interaction is weakened, indicating that the element diffusion mechanism in heavy rare-earth containing high-entropy materials homogenizes the sample, and significantly increases the coercivity. The mechanism of the coercivity is the nucleation of magnetization reversal domains in the grains of the hard magnetic phase. The magnetization mechanism is dominated by pinning at low magnetic fields and by nucleation at high magnetic fields, which is different from the magnetization mechanism of pure NdFeB and has some similarities with the self-pinning mechanism. The magnetic viscosity coefficient of (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Dy<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub> is larger than that of pure NdFeB. Due to the asynchrony of hard magnetic phase reversal and intergranular magnetic coupling in (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Tb<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub>, the magnetic viscosity coefficient is small with a large anisotropy field. This indicates that high-entropy samples reduce the magnetocrystalline anisotropy field barrier while increasing the magnetocrystalline coupling length. This suggests that the magnetization reversal of high-entropy rare-earth permanent magnet materials are significantly different from those of conventional rare earth permanent magnet materials and warrant further in-depth studies.

Distinct topological Hall responses in CeCu2-type EuZn2 and EuCd2 films

Rare-earth intermetallic compounds crystallized in AlB2-type and its low-symmetry derivative CeCu2-type structures potentially host diverse frustrated magnetic structures and rich magnetotransport phenomena. We report the film growth of CeCu2-type EuZn2 by molecular beam epitaxy and the observation of topological Hall responses highly contrastive to isostructural EuCd2. While their magnetization curves are rather similar, the topological Hall effect observed in EuZn2 is simpler, with the only one component enhanced at the magnetic transition field. EuZn2 may be a unique system for studying the magnetic domain boundary effect on topological Hall responses among the CeCu2-type rare-earth intermetallic compounds.

Calorimetric Studies of Phase Transformations in the La<sub>1 – x</sub>Y<sub>x</sub>Mn<sub>2</sub>Si<sub>2</sub> System

Differential scanning calorimetry (DSC) is used to determine the magnetic phase transformation temperatures of the La1 – xYxMn2Si2 (x = 0–1) alloys. For the compositions with х from 0 to 0.3, the temperature dependences of DSC signal exhibit λ-like endothermic effects observed near 300 K, which are related to the magnetic phase transition from the ferromagnetic to layered antiferromagnetic structure, and weak anomalies, which are observed in a temperature range of from 458 K for the composition with х = 0 to 323 К for the composition with х = 0.3 upon disordering of the layered antiferromagnetic structure. A clear endothermic peak corresponding to the disordering of interplane antiferromagnetic layered structure was found for the YMn2Si2. The data obtained are used to construct the magnetic phase diagram of the La1–xYxMn2Si2 system in a temperature range of 270–600 К. The differential scanning calorimetry is shown can be successfully used for the determination of temperatures of various magnetic phase transformations in rare-earth intermetallic compounds.

Machine-Learning Prediction of Curie Temperature from Chemical Compositions of Ferromagnetic Materials.

Room-temperature ferromagnets are high-value targets for discovery given the ease by which they could be embedded within magnetic devices. However, the multitude of potential interactions among magnetic ions and their surrounding environments renders the prediction of thermally stable magnetic properties challenging. Therefore, it is vital to explore methods that can effectively screen potential candidates to expedite the discovery of novel ferromagnetic materials within highly intricate feature spaces. To this end, we explore machine-learning (ML) methods as a means to predict the Curie temperature (Tc) of ferromagnetic materials by discerning patterns within materials databases. This study emphasizes the importance of feature analysis and selection in ML modeling and demonstrates the efficacy of our gradient-boosted statistical feature-selection workflow for training predictive models. The models are fine-tuned through Bayesian optimization, using features derived solely from the chemical compositions of the materials data, before the model predictions are evaluated against literature values. We have collated ca. 35,000 Tc values and the performance of our workflow is benchmarked against state-of-the-art algorithms, the results of which demonstrate that our methodology is superior to the majority of alternative methods. In a 10-fold cross-validation, our regression model realized an R2 of (0.92 ± 0.01), an MAE of (40.8 ± 1.9) K, and an RMSE of (80.0 ± 5.0) K. We demonstrate the utility of our ML model through case studies that forecast Tc values for rare-earth intermetallic compounds and generate magnetic phase diagrams for various chemical systems. These case studies highlight the importance of a systematic approach to feature analysis and selection in enhancing both the predictive capability and interpretability of ML models, while being devoid of potential human bias. They demonstrate the advantages of such an approach over a mere reliance on algorithmic complexity and a black-box treatment in ML-based modeling within the domain of computational materials science.

Effect of Hydrogenation on the Magnetic and Magnetocaloric Properties of Rare Earth Intermetallic Compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni

Effect of Hydrogenation on the Magnetic and Magnetocaloric Properties of Rare Earth Intermetallic Compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni

A Study of Rare Earth Intermetallic Compound La0.73Dy0.27Mn2Si2 by Raman Spectroscopy, Magnetic Force Microscopy, and Resonance Photoemission Spectroscopy

A Study of Rare Earth Intermetallic Compound La0.73Dy0.27Mn2Si2 by Raman Spectroscopy, Magnetic Force Microscopy, and Resonance Photoemission Spectroscopy

Estimation of magnetocaloric effect in multicomponent material Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2: Exploring high-entropy design

Polycrystalline rare earth intermetallic compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 has been synthesized by arc melting and it has MgCu2-type cubic crystal structure at 300 K (space group Fd-3m). Magnetization measurement on arc-melted Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 reveals a paramagnetic to ferromagnetic transition at ∼32 K (TC). The TC is close to the average value of the ferromagnetic transition temperatures of the end member GdNi2, TbNi2, DyNi2, HoNi2 and ErNi2 compounds. Using the field-dependent magnetization data measured around TC, isothermal magnetic entropy change (ΔSm) has been estimated. A maximum value of ΔSmmax = −14.3 J kg−1 K−1 is obtained at 27.5 K for 5 T field change. This value is significant when compared to that in the parent RNi2 (R = Gd, Tb, Dy, Ho and Er) compounds. The multicomponent compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 has also been prepared by melt-spinning under inert atmosphere. The melt-spun sample shows granular microstructure with an average grain size of ∼1 µm. It is found that the bulk magnetic properties are almost retained in the melt-spun sample and the magnetocaloric effect is nearly equal to that in arc-melted Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2. The relative cooling power is large and is about 568 J kg−1 and 531 J kg−1 for 5 T field change for the arc-melted and melt-spun Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Ni2 samples respectively.

Interstitial nitrogen-modified Y2Fe16SiNy compounds towards enhanced high-frequency magnetic properties

The rapid development of information technology urgently requires high-frequency soft magnetic materials with excellent electromagnetic performance. Herein, we synthesized the disordered dual-phase Y2Fe16Si intermetallic compound and introduced nitrogen atoms into its interstitial crystal sites by the gas-solid reaction, remarkably improving its magnetic and electromagnetic properties. The significant magneto-volume effect generated by introduced nitrogen atoms increases the compound's magnetization and Curie temperature, leading to increased permeability of Y2Fe16Si-paraffin composites. Furthermore, the synergistic effect of the magneto-volume and the chemical bonding change the compound's electric polarization by charge neutralization, dramatically decreasing the permittivity of Y2Fe16Si-paraffin composites upon nitrogenation. The decreased permittivity and increased permeability enhance the impedance matching and magnetic loss capability of the composites. Besides, the introduction of interstitial nitrogen gives rise to a higher ratio of the out-of-plane to in-plane anisotropy field of Y2Fe16Si due to anisotropic lattice expansion, which combines with enhanced magnetization to raise the Snoek limit and operating frequency of the composites. Consequently, Y2Fe16SiNy-paraffin composites exhibit the maximum effective absorption bandwidth (EAB) of 5.84 GHz in a thickness of 1.2 mm, and the minimum reflection loss (RLmin) of –50.52 dB in a thickness of 1.5 mm covering the Ku-band, demonstrating strong absorption, broad EAB with thin thickness and high operating frequency. This work shows the superiority of the interstitial atom effect in the high-frequency electromagnetic field, and the effect is applicable and scalable for rare-earth Fe-based intermetallic compounds to develop excellent microwave absorbers.

Effect of Pressure on Elastic Constants and Related Properties of Rare-Earth Intermetallic Compound TbNiAl

Effect of Pressure on Elastic Constants and Related Properties of Rare-Earth Intermetallic Compound TbNiAl

Magnetic properties and magnetocaloric effect of a metallic triangular lattice antiferromagnetic DyAl2Ge2 single crystal

We report the synthesis, magnetic susceptibility, magnetization, electrical resistivity, heat capacity, and magnetocaloric properties of the metallic triangular lattice antiferromagnetic DyAl2Ge2 single crystal. High-quality rare-earth intermetallic compound DyAl2Ge2 single crystals were synthesized by the metallic flux method. DyAl2Ge2 crystallizes in a trigonal CaAl2Si2-type structure with Dy atoms forming a triangular lattice in the ab plane. The paramagnetic-antiferromagnetic transition occurs at 8 K, as determined by temperature dependencies of magnetic susceptibility and heat capacity. No observable hysteresis was found in the field-induced antiferromagnetic to the ferromagnetic metamagnetic transition of DyAl2Ge2. The electrical resistivity shows an overall metallic behavior with an upturn at the ordering temperature. For a magnetic field change of 0–70 kOe, the maximum magnetic-entropy change is −14.2 J kg−1 K−1 at 11 K and the relative cooling power is 327 J kg−1 with the applied magnetic field along the ab plane.

Uncommon Magnetism in Rare-Earth Intermetallic Compounds with Strong Electronic Correlations

Rare-earth intermetallic compounds are characterised by the presence of a long-range magnetic order due to the interaction of local magnetic moments periodically located within the crystal lattice. This paper considers the possibility of forming an ordered state in cases where there is no opportunity to observe the local moment of the f-electronic shell in a traditional sense. These are, first of all, systems with a singlet ground state, as well as systems with fast spin fluctuations caused by a homogeneous intermediate-valence state of a rare-earth ion. Extensive experimental studies of these effects using neutron diffraction, neutron spectroscopy, and high-pressure studies of the magnetic phase diagram are presented and analysed, and the corresponding microscopic model representations are discussed. In particular, the possible origin of long-range magnetic order in mixed-valence compounds is analysed.

The effect of the X (X = Gd, Eu, La) substitution center position Tb on electronic, magnetic, and mechanical properties of TbFe2 by the DFT

Intermetallic compounds possess magnetostrictive properties and a unique interest in magnetic field detection. Here, the X (X = Gd, Eu, La) doped TbFe2, binary rare earth intermetallic compound is investigated using density functional theory (DFT). The electronic, magnetic, and mechanical properties of X-doped TbFe2 are systematically explored and compared. Then, energy bands and density of states (DOS), confirm that the X-doped TbFe2 compounds are metallic. Moreover, the asymmetry of the spin energy band and the anti-symmetric DOS indicate that X-doped TbFe2 is still magnetic. Further, magnetic research shows the magnetic moment of Gd-doped TbFe2 is highest upto 88.37 μB, which is about 1.7 times than that of TbFe2. Additionally, the four compounds (TbFe2 and X-doped TbFe2) are mechanically stable. Moreover, in contrast to the brittleness of TbFe2, X-doped TbFe2 becomes ductile. Hence, X-doped TbFe2 has improved the magnetic and ductile properties,which enhance its magnetic detection capabilities.

Valence electron structures and thermal and magnetic properties of RCo5 (R=light rare earth) intermetallic compounds with medium- and high-entropy design at R site

RCo5-type (R=light rare earth) medium- and high-entropy intermetallic compounds, which are designed by random occupation of equiatomic multiple rare earth elements at the rare earth site, are prepared by arc melting and vacuum heat-treatment technologies, and their crystal structures and magnetic properties are studied by X-ray diffraction and magnetic measurements. The empirical electron theory of solids and molecules is used to investigate their valence electron structures, thermal and magnetic properties. The theoretical bond lengths and magnetic moments match the experimental ones well. The study reveals that the thermal and magnetic properties are strongly related to the valence electron structures modulated by medium- and high-entropy design at rare earth. The medium and high entropized designs induce the increase of the covalence electron numbers nc. It is helpful for stabilizing the crystal structure. The number of covalence electron pair of the strongest R-CoI bond affects the melting point. The magnetic moments of RCo5-type medium- and high-entropy intermetallic compounds, which mainly originate from the 3d magnetic electrons of Co atoms, are modulated by medium and high entropized rare earth due to their exchange interactions. The magnetic moment of Co at the 2c site is larger than that of Co at the 3g site, which is due to the electron transformations from magnetic to covalence electron for bonding with the rare earth at the 3g site. Curie temperatures raise with the increasing 3d magnetic electron numbers of Co atom.

Magnetic properties of a multicomponent intermetallic compound Tb$_{0.25}$Dy$_{0.25}$Ho$_{0.25}$Er$_{0.25}$Al$_2$

Polycrystalline multicomponent Laves phase rare earth intermetallic compound Tb_{0.25}0.25 Dy_{0.25}0.25Ho_{0.25}0.25Er_{0.25}0.25Al_{2}2 has been synthesized by arc-melting and characterized by powder X-ray diffraction, magnetization and heat capacity measurements. The sample has MgCu_22-type cubic structure (space group Fd-3m) at 300 K. The compound Tb_{0.25}0.25Dy_{0.25}0.25Ho_{0.25}0.25Er_{0.25}0.25 Al_{2}2 orders ferromagnetically at 50 K (T_CC). This value is almost equal to the average of the ferromagnetic ordering temperatures of the individual RAl_22 (R = Tb, Dy, Ho and Er) compounds. Field dependence of magnetization below T_CC indicates soft-ferromagnetic nature. From the magnetization vs field data obtained near T_CC and the temperature dependence of heat capacity, low field magnetocaloric effect has been estimated.

Designing magnetocaloric materials for hydrogen liquefaction with light rare-earth Laves phases

Magnetocaloric hydrogen liquefaction could be a ‘game-changer’ for liquid hydrogen industry. Although heavy rare-earth based magnetocaloric materials show strong magnetocaloric effects in the temperature range required by hydrogen liquefaction (77–20 K), the high resource criticality of the heavy rare-earth elements is a major obstacle for upscaling this emerging liquefaction technology. In contrast, the higher abundances of the light rare-earth elements make their alloys highly appealing for magnetocaloric hydrogen liquefaction. Via a mean-field approach, it is demonstrated that tuning the Curie temperature (T C) of an idealized light rare-earth based magnetocaloric material towards lower cryogenic temperatures leads to larger maximum magnetic and adiabatic temperature changes (ΔS T and ΔT ad). Especially in the vicinity of the condensation point of hydrogen (20 K), ΔS T and ΔT ad of the optimized light rare-earth based material are predicted to show significantly large values. Following the mean-field approach and taking the chemical and physical similarities of the light rare-earth elements into consideration, a method of designing light rare-earth intermetallic compounds for hydrogen liquefaction is used: tuning T C of a rare-earth alloy to approach 20 K by mixing light rare-earth elements with different de Gennes factors. By mixing Nd and Pr in Laves phase (Nd, Pr)Al2, and Pr and Ce in Laves phase (Pr, Ce)Al2, a fully light rare-earth intermetallic series with large magnetocaloric effects covering the temperature range required by hydrogen liquefaction is developed, demonstrating a competitive maximum effect compared to the heavy rare-earth compound DyAl2.

On the magnetic and magnetocaloric properties of rare earth intermetallic compound Tb0.33Ho0.33Er0.33Ni

Polycrystalline rare earth intermetallic compound Tb0.33Ho0.33Er0.33Ni has been synthesized by arc melting under argon atmosphere. Powder X-ray diffraction data suggest that the compound Tb0.33Ho0.33Er0.33Ni crystallizes in orthorhombic structure at 300 K (FeB-type, space group Pnma). Temperature variation of magnetization reveals paramagnetic to ferromagnetic cross-over around 59 K (TC). The TC is close to the average value of the ferromagnetic transition temperatures of TbNi, HoNi and ErNi compounds. Isothermal magnetization has been measured as a function of magnetic field up to 70 kOe and the magnetocaloric effect around TC has been calculated.

EFFECT OF PRESSURE ON ELASTIC CONSTANTS AND RELATED PROPERTIES OF RARE-EARTH INTERMETALLIC COMPOUND TBNIAL

The Lennard-Jones potential approach is used to investigate the effect of pressure on the ultrasonic and elastic properties of the rare-earth ternary TbNiAl intermetallic compound. The second- and third-order elastic constants of TbNiAl are considered using the potential model. The pressure-dependent higher-order elastic constants are studied, and it is observed that the elastic constants of the TbNiAl compound increased monotonously with pressure. The hexagonal TbNiAl compound is mechanically stable up to the pressure 20 GPa according to the Born elastic stability criteria. The Voigt-Reuss-Hill approach is used to compute such elastic parameters as Young’s modulus, bulk modulus, Poisson’s ratio, and shear modulus in the pressure range 0-45 GPa. Hardness, melting temperature, and anisotropy are also determined for the intermetallic TbNiAl compound. The pressure-dependent velocities and attenuation of ultrasonic waves in this ternary compound are evaluated. The computation results are also satisfactory in estimating the Debye temperature and thermal conductivity Kmin under different pressure. It is observed that TbNiAl has a significant anisotropy at zero pressure, which becomes stronger as the pressure increased. This ternary compound behaves as its purest form at higher pressure and is more ductile, which is demonstrated by the minimum attenuation.

Unusual first-order magnetic phase transition and large magnetocaloric effect in Nd2In

A large magnetocaloric effect with its maximum near the boiling point of natural gas occurs in a rare-earth intermetallic compound ${\mathrm{Nd}}_{2}\mathrm{In}$. While behaviors of physical properties indicate that paramagnetic-ferromagnetic transformation supporting the large magnetocaloric effect is first order in nature, temperature-dependent crystallographic study reveals no changes in lattice symmetry and lack of discontinuities either in phase volume or lattice parameters. The borderline first-order nature of phase transformation in ${\mathrm{Nd}}_{2}\mathrm{In}$ is markedly different from conventional first-order magnetic transitions occurring in other members of the family -- isostructural ${\mathrm{Pr}}_{2}\mathrm{In}$ and nonisostructural ${\mathrm{Eu}}_{2}\mathrm{In}$.

Anisotropic magnetic property, magnetostriction, and giant magnetocaloric effect with plateau behavior in TbMn2Ge2 single crystal

The ternary RMn2Ge2 (R = rare earth) intermetallic compounds have attracted great attention due to their interesting magnetic behaviors and magnetotransport responses. Here, we reported our observation of anisotropic magnetic property, magnetostriction, and magnetocaloric effect (MCE) in TbMn2Ge2 single crystal. Below the transition temperature of Tb magnetic sublattices (T_{{text{C}}}^{{{text{Tb}}}} ~ 95 K), strong Ising-like magnetocrystalline anisotropy is observed with an out-of-plane ferromagnetic moments 5.98 μB/f.u. along the easy c axis, which is two orders of magnitude larger than that of field along a axis. Above T_{{text{C}}}^{{{text{Tb}}}}, a field-induced metamagnetic transition is observed from the spin-flip of Mn sublattices. During this transition, remarkable magnetostriction effect is observed, indicating of strong spin–lattice coupling. The responses of Tb and Mn sublattices to the magnetic field generate a giant magnetic entropy change (- Delta S_{M}) and large values of relative cooling power (RCP) and temperature-averaged entropy change (TEC). The calculated maximum magnetic entropy change (- Delta S_{M}^{max }), RCP, and TEC(10) with magnetic field change of 7 T along c axis reach 24.02 J kg−1 K−1, 378.4 J kg−1, and 21.39 J kg−1 K−1 near T_{{text{C}}}^{{{text{Tb}}}}, which is the largest among RMn2Ge2 families. More importantly, this giant MCE shows plateau behavior with wide window temperatures from 93 to 108 K, making it be an attractive candidate for magnetic refrigeration applications.

Magnetic incommensurability, short-range correlations, and properties ofHo7Rh3

The crystal structure, thermal properties, and magnetic state of the rare-earth intermetallic compound ${\mathrm{Ho}}_{7}{\mathrm{Rh}}_{3}$ was studied using the measurements of the AC and DC magnetic susceptibility, magnetization, specific heat and thermal expansion, as well as by neutron and synchrotron powder diffraction. Below the N\'eel temperature ${T}_{\mathrm{N}}=32$ K, an incommensurate antiferromagnetic (AFM) structure of the spin density wave (SDW) type was observed, described by the magnetic superspace group $Cmc{2}_{1.}{1}^{\ensuremath{'}}(00g)0sss$ and the propagation vector ${\mathbf{k}}_{\mathrm{IC}}=(0\phantom{\rule{0.16em}{0ex}}0\phantom{\rule{0.16em}{0ex}}0.389)$. Further cooling leads to the spin reorientation transition and squaring-up transformation of the SDW magnetic structure below ${T}_{t1}=22$ K. The spin reorientation transition is accompanied by the emergence of a ferromagnetic component in the incommensurate magnetic structure upon cooling below ${T}_{t2}=9$ K. Using neutron diffraction, the existence of a short-range antiferromagnetic order was revealed up to temperatures twice as high as ${T}_{\mathrm{N}}$. These short-range AFM correlations were found to affect the magnetic susceptibility and thermal expansion, while the crystal structure retains its hexagonal symmetry below and above the N\'eel temperature.