Rare Earth-transition Metal Research Articles

Interface-Triggered Spin-Magnetic Effect in Rare Earth Intraparticle Heterostructured Nanoalloys for Boosting Hydrogen Evolution.

Rare earth (RE) elements are attractive for spin-magnetic modulation due to their unique 4 f electron configuration and strong orbital couplings. Alloying RE with conventional 3d transition-metal (TM) is promising for the fabrication of advanced spin catalysts yet remains much difficulties in preparation, which leads to the mysteries of spin-magnetic effect between RE and 3d TM on catalysis. Here we define a solid-phase synthetic protocol for creating RE-3d TM-noble metal integrated intraparticle heterostructured nanoalloys (IHAs) with distinct Gd and Co interface within the entire Rh framework, denoted as RhCo-RhGd IHAs. They exhibit interface-triggered antiferromagnetic interaction, which can induce electron redistribution and regulate spin polarization. Theoretical calculations further reveal that active sites around the heterointerface with weakened spin polarization optimize the adsorption and dissociation of H2O, thus promoting alkaline hydrogen evolution catalysis. The RhCo-RhGd IHAs show a small overpotential of 11.3 mV at 10 mA cm-2, as well as remarkable long-term stability, far superior to previously reported Rh-based catalysts.

Tunable multistate field-free switching and ratchet effect by spin-orbit torque in canted ferrimagnetic alloy

Spin-orbit torque is not only a useful probe to study manipulation of magnetic textures and magnetic states at the nanoscale but also it carries great potential for next-generation computing applications. Here we report the observation of rich spin-orbit torque switching phenomena such as field-free switching, multistate switching, memristor behavior and ratchet effect in a single shot, co-sputtered, rare earth-transition metal GdxCo100−x. Notably such effects have only been observed in antiferromagnet/ferromagnet bi-layer systems previously. We show that these effects can be traced to a large anistropic canting, that can be engineered into the GdxCo100−x system. Further, we show that the magnitude of these switching phenomena can be tuned by the canting angle and the in-plane external field. The complex spin-orbit torque switching observed in canted GdxCo100−x not only provides a platform for spintronics but also serves as a model system to study the underlying physics of complex magnetic textures and interactions.

Synthesis of Samarium Nitride Thin Films on Magnesium Oxide (001) Substrates Using Molecular Beam Epitaxy

Rare-earth nitrides are an exciting family of materials with a wide variety of properties desirable for new physics and applications in spintronics and superconducting devices. Among them, samarium nitride is an interesting compound reported to have ferromagnetic behavior coupled with the potential existence of p-wave superconductivity. Synthesis of high-quality thin films is essential in order to manifest these behaviors and understand the impact that vacancies, structural distortions, and doping can have on these properties. In this study, we report the synthesis of samarium nitride monocrystalline thin films on magnesium oxide (001) substrates with a chromium nitride capping layer using molecular beam epitaxy (MBE). We observed a high-quality monocrystalline SmN film with matching orientation to the substrate, then optimized the growth temperature. Despite the initial 2 nm of growth showing formation of a potential samarium oxide layer, the subsequent layers showed high-quality SmN, with semiconducting behavior revealed by an increase in resistivity with decreasing temperature. These promising results highlight the importance of studying diverse heteroepitaxial schemes and open the door for integration of rare-earth nitrides and transition metal nitrides for future spintronic devices.

Investigation of physical properties of Ba2NdX(X=Nb, Ta)O6 double perovskites for renewable energy applications

Alkali metals at the A site, coupled with rare earth transition metals featuring partly filled 4f and d orbitals at B and B’ sites in A2BB’O6 structure of double perovskites, induce complex d-f electron interactions. Present study explores the rare earth-based double perovskites Ba2NdNbO6 and Ba2NdTaO6, investigating their structural, optoelectronic, magnetic, and thermoelectric characteristics using first principles method. Computational analyses confirm the stable cubic symmetry and ferromagnetic ground state of both compounds. Negative formation enthalpies underline their thermodynamic stability. Spin polarized electronic band structures reveal direct–indirect degeneracy near the Fermi level, dominated by Nd-4f electrons. Optical investigations indicate absorption onset edges at 4.0 eV and significant absorbance peaks in the 6–10 eV range. Furthermore, the investigation into thermoelectric figure of merit reveals capability of Ba2NdNbO6 and Ba2NdTaO6 to efficiently convert heat energy in thermoelectric devices. These findings provide information for potential applications of investigated compounds in thermoelectric (TE) and optoelectronic devices; e.g., in optical absorbers, TE coolers and generators, and photonic devices.

Dual-Atom P-Co-Dy Charge-Transfer Bridge on Black Phosphorus for Enhanced Photocatalytic CO2 Reduction.

The synergistic effect of rare earth single-atoms and transition metal single-atoms may enable us to achieve some unprecedented performance and characteristics. Here, Co-Dy dual-atoms on black phosphorus with a P-Co-Dy charge-transfer bridge are designed and fabricated as the active center for the CO2 photoreduction reaction. The synergistic effect of Co-Dy on the performance of black phosphorus is studied by combining X-ray absorption spectroscopy, ultrafast spectral analysis, and in situ technology with DFT calculations. The results show that the Co and Dy bimetallic active site can promote charge transfer by the charge transfer bridge from P to Dy, and then to Co, thereby improving the photocatalytic activity of black phosphorus. The performance of catalysts excited at different wavelength light indicates that the 4G11/2/2I15/2/4F9/2→6H15/2 and 4F9/2→6H13/2 emissions of Dy can be absorbed by black phosphorus to improve the utilization of sunlight. The in situ DRIFTS and density functional theory (DFT) calculations are used to investigate the CO2 photoreduction pathway. This work provides an depth insight into the mechanism of dual-atom catalysts with enhanced photocatalytic performance, which helps to design novel atomic photocatalysts with excellent activity for CO2 reduction reactions.

Multinuclear solid state NMR spectroscopy of ternary rare-earth silicides RET 2Si2 and germanides LaT 2Ge2 (RE = Sc, Y, La, Lu; T = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au)

Abstract A series of ternary rare earth – transition metal – tetrelides RET 2 Tt 2 (RE = Sc, Y, La, Lu; T = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au; Tt = Si, Ge) was synthesized by arc melting of the elements and subsequent annealing. The samples were characterized by powder X-ray diffraction and in addition, the structures of REOs2Si2 (RE = Y, La, Lu), LaAu2Si2, LaAg2Ge2 and LaAu2Ge2 were refined from single crystal X-ray diffractometer data. The tetrelides crystallize with the ThCr2Si2 type (I4/mmm) except the platinum compounds which adopt the klassengleiche superstructure of the CaBe2Ge2 type (P4/nmm). The transition metal atoms have tetrahedral tetrel coordination and the tetrahedra condense to layers via common edges. The stacking of these layers leads to Tt−Tt bonds in the ThCr2Si2 type phases and heteroatomic T−Tt bonds in the CaBe2Ge2 type phases. The rare earth atoms fill larger cages within these three-dimensional networks (coordination number 16 with RE@T 8 Tt 8) with site symmetries 4/mmm (ThCr2Si2 type) and 4mm (CaBe2Ge2 type). Systematic multinuclear solid state NMR spectroscopic investigations allowed observing the effect of the involved rare-earth metal, transition metal and tetrel group element, respectively. In particular, 29Si isotropic resonance shifts can be predicted from element-specific increments and interatomic Si–Si bonding interactions manifest themselves in axially symmetric magnetic shielding anisotropies.

New soft magnetic materials ([formula omitted])[formula omitted]B with tunable magnetic anisotropy

Soft magnetic materials play important roles in both power generation and conversion devices with the rapid development of power semiconductors, however, finding new soft magnetic materials is an urgent problem. It was found that (Y1−xSmx)2Fe14B (0≤x≤1) compounds prepared by vacuum induction melting have a tetragonal structure. In (0≤x≤1) range, the saturation magnetization is higher than 110 A⋅m2/kg, the Curie temperature is over 290 °C, the coercivity and the remanence are less than 5729.8 A⋅m−1 and 7 A⋅m2/kg, respectively. Furthermore, with increasing x the directions of easy magnetization change from the c-axis (x=0.00) to the cone plane (x=0.15), and then to the ab-plane (x≥0.30). For x=0.15 compound, the permeability at 100 kHz is 11.8, that is beyond all of existing rare earth magnetic materials. These indicate that (Y1−xSmx)2Fe14B compounds are the promising candidate for proper soft magnetic materials without x=0. Our work extends the function of rare earth transition metal intermetallic compounds, which open a new way to find advanced soft magnetic materials.

Unravelling the Mechanism of CO2 Activation: Insights Into Metal-Metal Cooperativity and Spin-Orbit Coupling with {3d-4f} Catalysts.

Converting CO2 into useful chemicals using metal catalysts is a significant challenge in chemistry. Among the various catalysts reported, transition metal lanthanide hybrid {3d-4f} complexes stand out for their superior efficiency and site selectivity. However, unlike transition metal catalysts, understanding the origin of this efficiency in lanthanides poses a challenge due to their orbital degeneracy, rendering the application of DFT methods ineffective. In this study, we employed a combination of density functional theory (DFT) and ab initio CASSCF/RASSI-SO calculations to explore the mechanism of CO2 conversion to cyclic carbonate using a 3d-4f heterometallic catalyst for the first time. This work unveils the importance of 3d and 4f metal cooperativity and the role of individual spin-orbit states in dictating the overall efficiency of the catalyst.

Structural, optical and photoluminescence characteristics of apatite type lanthanide silicates

This article reports the solid state synthesis of apatite type rare earth-transition metal silicates Nd4MnSi3O13 and Sm4MnSi3O13. These oxyapatite type lanthanide silicates were characterized through structural, micro structural, optical and photoluminescence properties. The indexed X-ray diffraction patterns and Raman analysis confirm that both the samples crystallize in single phase hexagonal symmetry with space group P63/m. Transmission electron microscopy images along with electron diffraction pattern indicate the good crystalline nature of both the samples which further support the results obtained from X-ray diffraction study. The optical band gap energies are found to be 4.1 eV and 3.9 eV for Nd4MnSi3O13 and Sm4MnSi3O13 respectively. The wide optical band gap values of these semiconductor silicates make enable them for fundamental and technological applications. The luminescent properties and CIE coordinates showed the green-yellow emission of these synthesized silicates which further indicate that these compounds may have uses in solid state lighting because of the tunable luminescence.

Anionic and Magnetic Ordering in Rare Earth Tantalum Oxynitrides with an n = 1 Ruddlesden-Popper Structure.

The new compounds R2TaO4-xNx with R = La, Ce, Nd, and Eu and 1.20 ≤ x ≤ 2.81 have been obtained by a solid-state reaction between metal nitrides and oxides or oxynitrides under N2 gas at temperatures between 1200 and 1700 °C. They are the first examples of rare earth transition metal oxynitrides with an n = 1 Ruddlesden-Popper structure and show different anion stoichiometries, crystal structures, and magnetic properties. Synchrotron X-ray powder diffraction and electron diffraction indicate that the lanthanum, cerium, and neodymium compounds crystallize in the orthorhombic space group Pccn, with cell parameters a = 5.72949(2), b = 5.73055(5), and c = 12.77917(6) Å for La2TaO1.31N2.69, a = 5.70500(5), b = 5.71182(4), and c = 12.61280(7) Å for Ce2TaO1.19N2.81, and a = 5.70466(3), b = 5.70476(5), and c = 12.32365(5) Å for Nd2TaO1.46N2.54. In contrast, Eu2TaO2.80N1.20 shows a tetragonal I41/acd superstructure doubling the c axis, with parameters a = 5.71867(2) and c = 25.00092(19) Å. Refinement of neutron powder diffraction data of Ce2TaO1.19N2.81 indicated the nitrogen order in the two equatorial positions of the tantalum octahedron, with refined N/O occupancies of 0.930(7)/0.070 and 0.876(13)/0.124, and the axial position is occupied by 50% of each anion. This anion ordering agrees with the distribution predicted by Pauling's second crystal rule. Magnetization measurements show that the cerium and europium compounds are ordered magnetically at low temperatures, while the neodymium compound remains paramagnetic down to 2 K, as a consequence of suppression of the effective magnetic moment of the latter when reducing the temperature.

Element-specific Curie temperatures and Heisenberg criticality in ferrimagnetic Gd6(Mn1−xFex)23 via Kouvel-Fisher analysis

Many large unit-cell rare-earth transition metal ternary alloys of the type Ra(M1−xM’x)b exhibit non-monotonic ferrimagnetic Curie temperatures (TC) coupled to monotonic composition-controlled magnetization. Its origin remains an important long-standing puzzle in the absence of studies probing their temperature-dependent element-specific magnetism. Here, in order to resolve this issue and identify design principles for new R-M-M’ permanent magnets, we carry out x-ray magnetic circular dichroism (XMCD) for the series Gd6(Mn1−xFex)23, x = 0.0 − 0.75. The results show that the net Mn-moment reduces and switches from parallel to antiparallel for x ≥ 0.2, while the Fe-moment is always antiparallel to the Gd-moment. Kouvel-Fisher analyses of XMCD data reveals distinct sublattice TC’s and 3D Heisenberg criticality. Band structure calculations show magnetic moments and density of states consistent with experiments. The magnetic phase diagram shows three regions characterized by (i) Mn-sublattice bulk-TC > Gd-sublattice TC, (ii) a reduced common-TC for all sublattices, and (iii) Fe-sublattice bulk-TC > Gd-sublattice TC. The Mn-moment switching and gradual increase of Fe-moment combine to cause non-monotonic TC’s with monotonic magnetization. The study indicates the importance of element-specific TC’s for tuning magnetic properties.

Evidence and Practical Applications of Site Occupancy Theory (SOT) of Eu3+ in Scheelite Compounds.

The determination of the site occupancy of activators in phosphors is essential for precise synthesis, understanding the relationship between their luminescence properties and crystal structure, and tailoring their properties by modifying the host composition. Herein, one simple method was proposed to help determine the sites at which the doping of rare earth ions or transition metal ions occupies in the host lattice through site occupancy theory (SOT) for ions doped into the matrix lattice. SOT was established based on the fact that doping ions preferentially occupy the sites with the lowest bonding energy deviations. In order to provide detailed experimental evidence to prove the feasibility of SOT, several scheelite-type compounds were successfully synthesized using a high-temperature solid-phase method. When Eu3+ ions occupy a similar surrounding environment site, the photoluminescence spectra of the activators Eu3+ are similar. Therefore, by comparing the intensity ratio of photoluminescence spectra and the mechanism of all transitions of KEu(WO4)2, KY(WO4)2:Eu3+, Na5Eu(WO4)4, and Na5Y(WO4)4:Eu3+, it was proved that SOT can successfully confirm the site occupation when doped ions enter the matrix lattice. SOT was further applied to the sites occupied by Eu3+ ion-doped LiAl(MoO4)2 and LiLu(MoO4)2.

Electronic structure along Sm[formula omitted]Co[formula omitted]Ge[formula omitted] twin boundaries

Ln2Co3Ge5 (Ln = lanthanide) intermetallics possess intriguing electronic and magnetic properties. The compound Sm2Co3Ge5 exhibits antiferromagnetic ordering coupled with a magnetic moment that exceeds the theoretical moment of trivalent Sm suggesting a magnetic contribution from Co. Twinning is observed in Sn flux-grown monoclinic Sm2Co3Ge5 along (100) planes. While the influence of twin boundaries on superconducting oxides and 2D-materials is well-studied, its effects on bulk lanthanide-based intermetallics are rarely explored. Using monochromated electron energy-loss spectroscopy (EELS) and high-resolution transmission electron microscopy (TEM), we investigate the impact of twin domains on the local strain and electronic structure of Sm2Co3Ge5. The boundaries between twinned domains primarily exhibit shear strain and have a constant oxidation state, but fine structure emerges in the Co L2,3 edges at twin boundaries, indicative of 3d-electron hybridization and occupation of states not present in bulk grain spectra. These findings provide insights into tuning the bulk properties of lanthanide-transition metal systems with complex magnetism.

High entropy La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 with tailored eg occupancy and transition metal-oxygen bond properties for oxygen reduction reaction

Forming high entropy oxide provides a feasible approach to finding a balance among moderate eg occupancy, high transition metal-oxygen (TM-O) covalency, and lattice energy, which is essential to ensure efficient and durable oxygen reduction reaction (ORR) process for perovskite lanthanide-transition metal oxides (LaTMO3). However, due to the compositional complexity, clarifying the relevance among the high entropy components, eg occupancy, TM-O properties, and ORR performance still remains a challenge. Herein, adopting the B site entropy-driven strategy, a series of LaTMO3 (TM = Cr, Mn, Fe, Co, Ni) with tunable eg occupancy and TM-O bond properties are synthesized, and the correlations between high entropy elements, eg occupancy, TM-O properties, and ORR performances are revealed quantitively based on the crystal field theory and the Phillips–Van Vechten–Levine (P–V–L) valence bond theory. High entropy La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 delivers a low overpotential of 493 mV (vs. 503 mV for LaMnO3) and a minuscule decline by only 1.7% (vs. 4.4% for LaMnO3) in half wave potential after 10,000 cycles, which can be associated with the tailored eg occupancy (1.06) and the significant enhancement in both TM-O covalency (4%) and lattice energy (691.75 kJ mol–1). This work not only demonstrates the prospects of high entropy LaTMO3 in the ORR field but also provides a new perspective for the quantitative analysis of the structure-activity relationship for high entropy oxide ORR catalysts.

Early diagenetic control on the enrichment and mobilization of rare earth elements and transition metals in buried ferromanganese crust

Ferromanganese crusts on seamounts represent a major reservoir of various critical metal elements (e.g., rare earth elements and transition metals) and hold substantial economic value. However, current research primarily focuses on crusts that are exposed to seawater, and little is known about the resource potential of buried crusts in sediments and the impact of early diagenesis on buried crusts. Here, we present in-situ high-resolution major and trace element analyses of a buried crust from the western Pacific Ocean to unravel how rare earth elements and transition metals are enriched and mobilized as burial. The elemental profiles of the buried crust indicate that as the crust is buried, dissolved nickel (Ni) and copper (Cu) are gradually released from it into the porewater. Manganese and cobalt (Co) contents of the buried crust remain relatively constant, while rare earth elements are incorporated into the buried crust. Collectively, the early diagenesis leads to the release of Ni and Cu into the porewater, whereas it facilitates the fixation of rare earth elements within the buried crust. Given the widespread distribution of buried crusts in modern oceans, they represent a potential resource for future economic extraction of critical metals, particularly rare earth elements and Co.

From toggle to precessional single laser pulse switching

With the advent of nanotechnologies, it has been possible to extend the number of stimuli that can be used to control the state of a magnetic nanostructure. Among those stimuli, single laser pulse excitation allows, under certain conditions, to obtain energy-efficient ultrafast magnetization reversal. With this respect, two different types of single pulse switching mechanisms have been reported. The first one consists in a sub-picosecond ultrafast toggle switching, which was observed mainly in Gd based alloys. The second type relies on sub-nanosecond precessional switching occurring in rare earth–transition metal alloys/multilayers. Here, we demonstrate that single pulse all optical switching is achieved in Co68Tb32/Co100−xGdx/Co68Tb32 trilayers in which the behavior can be tuned from toggle to precessional by changing the composition of the Co100−xGdx alloy.

Thermoelectric Properties of N-type Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>x</sub>SbBi Materials Doped with La and Mn

Mg<sub>3</sub>Sb<sub>2</sub>-based n-type materials are consisted of earth-abundant elements and possess comparable thermoelectric properties with n-type Bi<sub>2</sub>Te<sub>3</sub> at low temperatures, which make them promising candidates for cooling and power generation applications in terms of cost and performance. Substitution of Sb atom with chalcogen elements (Te, Se S) is a conventional method for n-type doping, but doping cations such as rare-earth elements and transition metals is also widely studied for its unique advantages. In this study, La and Mn were selected for co-doping of Mg3SbBi, and the thermoelectric performances of the doped materials were investigated. Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>x</sub>SbBi (0  <i>x</i>  0.015) polycrystalline samples were made by sintering the fine powders of the mother alloy after arc melting, in which elemental Mn and LaSb compound were included for n-type dual doping. Considering the loss of Mg at elevated temperatures by vaporization, the molar ratio of Mg, Sb, and Bi in the mixture for arc melting was set to 4 : 1 : 1 with excess Mg. Analysis shows that all the samples are n-type, and the electrical conductivity of Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi increased by 62% from the Mn-free Mg<sub>3</sub>La<sub>0.005</sub>SbBi at 298 K. In addition, the lattice thermal conductivity (<i><sub>lat</sub></i>) decreased with increasing Mn content in the measured temperature range of 298-623 K. The minimum value of <i><sub>lat</sub></i> was about 0.60 W m<sup>-1</sup>K<sup>-1</sup> in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi at 523 K, which is about 19% smaller than that of the Mn-free sample. As a result of these enhancements in thermoelectric performance, the maximum figure of merit (<i>zT<sub>max</sub></i>) of 1.12 was obtained in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.01</sub>SbBi and Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi at 573 K, and the <i>zT</i> at 298 K increased by 73% to 0.35 in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi compared to Mn-free Mg<sub>3</sub>La<sub>0.005</sub>SbBi, which is beneficial to room-temperature applications.

A data-driven approach to predict the saturation magnetization for magnetic 14:2:1 phases from chemical composition

14:2:1 phases enable permanent magnets with excellent magnetic properties. From an application viewpoint, saturation polarization, Curie temperature, and anisotropy constant are important parameters for the magnetic 14:2:1 phases. Novel chemical compositions that represent new 14:2:1 phases require especially maximum saturation magnetization values at application-specific operating temperatures to provide maximum values for the remanence and the maximum energy density in permanent magnets. Therefore, accurate knowledge of the saturation magnetization Ms is important. Ms gets affected by chemical composition in a twofold way, with chemical composition significantly influencing both magnetic moments and crystal structure parameters. Therefore, for magnetic 14:2:1 phases, we have developed a regression model with the aim to predict the saturation magnetization in [µB/f.u.] at room temperature directly from the chemical composition as input features. The dataset for the training and testing of the model is very diverse, with literature data of 143 unique phases and 55 entries of repeated phases belonging to the ternary, quaternary, quinary, and senary alloy systems. Substitutionally dissolved elements are heavy and light rare earth elements, transition metals, and additional elements. The trained model is a voting regressor model with different weights assigned to four base regressors and has generalized well, resulting in a low mean absolute error of 0.8 [µB/f.u.] on the unseen test set of 52 phases. This paper could serve as the basis for developing novel magnetic 14:2:1 phases from chemical composition.

DFT + U study of the structural, electronic and magnetic properties in the EuCoO3, EuFeO3, and EuCo0.5Fe0.5O3 type perovskite compounds

The study of the interactions between rare-earth elements and transition metals plays a crucial role in understanding the diverse magnetic states observed in systems with ABO3 perovskite structure. Exploring their behavior and the impact on their physical properties has such a significant interest, especially considering their potential applications across various technological sectors. In this research, we investigated the structural, electronic, and magnetic properties of three systems EuCoO3 (ECO), EuFeO3 (EFO), and EuCo0.5Fe0.5O3 (ECFO). We used the density functional theory based on the Hubbard model (DFT + U) approach to accomplish this. Our findings reveal that the ECO system has a bandgap of 1.052 eV for the spin down channel, while the spin up channel exhibits band gap of 1.066 eV, while the EFO system exhibits a slightly smaller bandgap of 0.958 eV. On the other hand, the ECFO system displays a bandgap value of approximately 0.961 eV for the spin-up channel and 1.6 eV for the spin-down channel. Furthermore, we observed an antiferromagnetic behavior in the EFO system, whereas the ECO and ECFO systems exhibit ferromagnetic behavior. These results provide insight into the distinct magnetic properties of these materials and contribute to our understanding of their potential applications as functional devices in various technological fields.

The γ” Phase in Mg-RE-TM Alloys: A Review on the Structure and Stability of the γ” Phase and Its Effect on Mechanical Properties

In magnesium–rare earth–transition metal (Mg-RE-TM) alloys, the γ” phase (with a hexagonal structure with the space group P6¯2m) is a critical strengthening phase that can significantly improve their mechanical properties. However, compared to other phases in Mg-RE-TM alloys, research on the γ” phase is less documented, and an understanding of the γ” phase is not well established. As a result, different models of the structure of the γ” phase have been proposed. In this review, we summarize these structural models and find that the γ” phase is different from the Guinier–Preston (G.P.) zone, as revealed via Cs-corrected high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and density functional theory (DFT) calculations. In addition, we briefly summarize the stability of the γ” phase and its effect on the mechanical properties of Mg-RE-TM alloys.