Ni Sublattice Research Articles

Signature of Superconductivity in Pressurized Trilayer-nickelate Pr4Ni3O10-δ

Abstract The discovery of high-temperature superconductivity in La3Ni2O7 and La4Ni3O10 under pressure has drawn extensive attention. Herein, we report systematic investigations on the structure, magnetism, and electrical resistance evolutions of Pr4Ni3O10-δ polycrystalline samples under various pressures. Pr4Ni3O10-δ exhibits density wave transitions on Ni and Pr sublattices at about 157.6 K and 4.3 K, respectively, and the density wave can be progressively suppressed by pressure. A structural transformation from the monoclinic P21/a space group to the tetragonal I4/mmm occurs at around 20 GPa. An apparent drop in resistance with evident magnetic field dependence is observed as pressure above 20 GPa, indicating the emergence of superconductivity. The discovery of superconductivity in Pr4Ni3O10-δ broadens the family of nickelate superconductors. Pr4Ni3O10-δ provides a new platform for investigating the mechanisms of superconductivity in the Ruddlesden–Popper phases of nickelates.

Optimizing precipitation hardening in a L12-strengthened medium-entropy alloy via tuning the anti-phase boundary energy

In present work, we investigate the elemental partition behaviors in L12 ordered intermetallics and its influence on mechanical properties in a Ni-Co-Cr-Al-Ta medium-entropy alloy (MEA) system through a combination of density functional theory (DFT) calculations and experimental investigation. Our finding reveal that Ta has a strong tendency to occupy Al sublattice, while Co prefers Ni sublattice, Cr, on the other hand, randomly occupy Al and Ni sublattices, resulting in the formation of the multicomponent (Ni, Co, Cr)3(Al, Ta, Cr) L12 intermetallics. Among the constituent elements, Ta is identified as an efficient element for enhancing hardening of the alloy. Furthermore, we demonstrate that improving Ta/Al ratio leads to a significant increase in anti-phase boundary (APB) energy, resulting in superior precipitation hardening effects and excellent mechanical properties. Our founding provide valuable insights for further the rationally design and rapid development of high performance L12-strengthened alloys.

Transformation of the crystal structure of Ni0.5TiSe2 under in situ heating.

The crystal structure of the Ni0.5TiSe2 compound has been studied in situ in the temperature range of 25-1000 °C using synchrotron radiation X-ray diffraction. The previously known order-disorder transition in the Ni sublattice at ∼100 °C was found to be a second-order phase transition and belongs to the 3D Ising universality class. Reversible extraction of nickel selenides was observed in the temperature range of 275-975 °C. It was explained in terms of Ni extraction from Ni0.5TiSe2 due to the thermal widening of the Ni 3d/Ti 3d/Se 4p impurity band. The Ni-TiSe2 phase diagram follows the typical pattern of MxTiSe2 (M - transition metal) compounds.

Revisiting the metal-to-metal transition in 2H-AgNiO2

The layered delafossite compound AgNiO2 with stacking symmetry undergoes a structural metal-to-metal transition at . It has been described in the past as a charge-ordering transition, where local S = 1 spins are formed on part of the Ni sites. By means of first-principles many-body calculations, we show that the transition is in fact a site-selective Mott transition on the Ni sublattice with only minor charge differentiation. Key to this finding is the uncovering of ligand-hole physics, rendering a Ni2+ instead of a formal Ni3+ oxidation state, in conjunction with strong local Coulomb repulsions.

Unveiling the Co effect on the temporal evolution kinetics of γ′ phase in Ni–Al–Co model superalloys via CALPHAD–informed phase field simulations

Co is a valuable γ solid solution strengthening element in nickel-based superalloys that improves their microstructure and creep resistance. However, the impact of Co additions on the kinetics of γ′ precipitation remains controversial. In this study, we conducted CALPHAD-informed phase field simulations to quantitatively analyze the γ′ precipitation process in Ni–Al–Co model superalloys and uncover the Co effect on the temporal evolution kinetics of the γ′ phase. Our simulations revealed that the γ′ coarsening rate initially decreases, then increases at 1173 K with increasing Co content, a change that can be attributed to the competition between the γ/γ′ lattice misfit and interdiffusion coefficients. Although Co is a γ-stabilized element, our calculations and previous experiments show an anomalous increase in γ′ volume fraction with increasing Co concentration, which is linked to variations in elemental partitioning behaviors between the γ matrix and γ′ phase. Furthermore, the unique partitioning behavior of Ni suggests partial replacement of Al atoms at the corner site of γ′-Ni3(Al, Ni) sublattice by Ni atoms. Our research offers a new perspective on the effect of Co concentration on the kinetics of γ′ precipitation in Ni–Al–Co model superalloys and outlines a guideline for designing novel multicomponent superalloys with superior microstructural stability.

Sublattice-Dependent Antiferromagnetic Transitions in Rare Earth Nickelates.

Perovskite rare earth nickelates exhibit remarkably rich physics in their metal-insulator and antiferromagnetic transitions, and there has been a long-standing debate on whether their magnetic structures are collinear or noncollinear. Through symmetry consideration based on the Landau theory, we discover that the antiferromagnetic transitions on the two nonequivalent Ni sublattices occur separately at different Néel temperatures induced by the O breathing mode. It is manifested by two kinks on the temperature-dependent magnetic susceptibilities with the secondary kink being continuous in the collinear magnetic structure but discontinuous in the noncollinear one. The prediction on the secondary discontinuous kink is corroborated by an existing magnetic susceptibility measurement on bulk single-crystalline nickelates, thus strongly supporting the noncollinear nature of the magnetic structure in bulk nickelates, thereby shedding new light on the long-standing debate.

Role of intersublattice exchange interaction in ultrafast longitudinal and transverse magnetization dynamics in permalloy

We report on element-specific measurements of ultrafast demagnetization and magnetization precession damping in permalloy thin films. Magnetization dynamics induced by an optical pump at 1.5 eV is probed simultaneously at the ${M}_{2,3}$ edges of Ni and Fe with high-order harmonics for moderate demagnetization rates (less than 50%). The role of the intersublattice exchange interaction in both longitudinal and transverse dynamics is analyzed with a Landau-Lifshitz-Bloch description of ferromagnetically coupled Fe and Ni sublattices. It is shown that the intersublattice exchange interaction governs the dissipation during demagnetization as well as precession damping of the magnetization vector.

Ductility reduction upon cobalt substitution in B2 NiTi

This paper reports the effect of ternary addition of cobalt to B2 NiTi by varying concentrations × = 0.125, 0.25 and 0.375 in Ni0.5−xCoxTi0.5 and the impact on their crystal structure, electronic and mechanical properties using first-principles calculations. The third element Co was substituted on both Ni and Ti sub-lattices using the supercell approach, site preference energy and formation energy suggest the preference of Co substitution on Ni sub-lattice agreeing with literature. The evolution of the electronic and mechanical properties from undoped NiTi to TiCo by substitution of Ni by Co is hereby discussed. Young’s (E) and shear (G) modulus is found to gradually increase as concentration (x) is increased. Importantly, ductility decreases with increasing cobalt concentration. From DOS, it is observed that the delocalized d states are reduced upon increasing Co addition due to strong d-d hybridization which reduces the metallicity and in turn ductility. This increase in Young’s modulus and decrease in ductility upon cobalt addition is indicative of the overall stiffness and resistance to deformation.

Zigzag magnetic order and possible Kitaev interactions in the spin-1 honeycomb lattice KNiAsO4

Despite the exciting implications of the Kitaev spin Hamiltonian, finding and confirming the quantum spin-liquid state have proven incredibly difficult. Recently, the applicability of the model has been expanded through the development of a microscopic description of a spin-1 Kitaev interaction. Here we explore a candidate spin-1 honeycomb system, ${\mathrm{KNiAsO}}_{4}$, which meets many of the proposed criteria to generate such an interaction. Bulk measurements reveal an antiferromagnetic transition at $\ensuremath{\sim}19$ K which is generally robust to applied magnetic fields. Neutron diffraction measurements show magnetic order with a $\mathbf{k}=(\frac{3}{2},0,0)$ ordering vector which results in the well-known ``zigzag'' magnetic structure thought to be adjacent to the spin-liquid ground state. Field-dependent diffraction shows that while the structure is robust, the field can tune the direction of the ordered moment. Inelastic neutron scattering experiments show a well-defined gapped spin-wave spectrum with no evidence of the continuum expected for fractionalized excitations. Modeling of the spin waves shows that the extended Kitaev spin Hamiltonian is are generally necessary to model the spectra and reproduce the observed magnetic order. First-principles calculations suggest that the substitution of Pd on the Ni sublattice may strengthen the Kitaev interactions while simultaneously weakening the exchange interactions thus pushing ${\mathrm{KNiAsO}}_{4}$ closer to the spin-liquid ground state.

Cobalt-Induced Phase Transformation of Ni3Ga4 Generates Chiral Intermetallic Co3Ni3Ga8

The scientific community has found immense difficulty to focus on the generation of chiral intermetallics compared to the chiral molecular structure, probably due to the technical difficulty in producing them as no general controlled protocol is available. Herein, using a conventional metal flux technique, we have discovered a new ternary intermetallic Co3Ni3Ga8, substituting Co at the Ni sublattice in a highly symmetric Ni3Ga4 (Ia3̅d). Co3Ni3Ga8 crystallizes in the I4132 space group, a Sohncke type, and can host the chiral structure. To the best of our knowledge, this is the first report of a ternary intermetallic crystallizing in this space group. The chiral structure of Co3Ni3Ga8 is comprehensively mapped by various techniques such as single-crystal X-ray diffraction (XRD), synchrotron powder XRD, X-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM) and theoretically studied using density functional theory. The discovery of this chiral compound can inspire the researchers to design hidden ternary chiral intermetallics to study the exotic electrical and magnetic properties.

Uncovering the origin of physical properties associated with magneto-structural transition of Ni-Mn-In-X alloys by ab initio methods

Ni-Mn-In metamagnetic shape memory alloys exhibit magneto-structural coupling features during martensitic transformation. In the present work, the composition-dependent crystal structure, phase stability, elastic and magnetic properties of the off-stoichiometric Ni2Mn1.5In0.5 alloy doped with the fourth element X (X = Co, Fe, and Cu) are investigated by using the ab initio calculations. Results show that Co prefers to occupy the Ni sublattice, Fe or Cu takes the Mn site. Doping X constituent reduces the stability of the austenite (A) and non-modulated (NM) martensite. For doped Co, martensitic transformation can occur at 0 ≤ x ≤ 0.75, and there exists a magneto-structural coupling characteristic with the Co range in 0 ≤ x ≤ 0.25. For the case of Fe or Cu doping, the martensitic transformation is accompanied by the change of magnetism. The results of elastic properties indicate that the plasticity and toughness increase significantly with Fe or Cu doping and decrease with Co doping. Furthermore, the origin of the physical properties associated with the magneto-structural coupling transition is explained in terms of the electronic density of states.

Influence of the magnetic sublattices in the double perovskite LaCaNiReO6

The magnetism of double perovskites is a complex phenomenon, determined from intra- or interatomic magnetic moment interactions, and strongly influenced by geometry. We take advantage of the complementary length and timescales of the muon spin rotation, relaxation, and resonance (${\ensuremath{\mu}}^{+}\mathrm{SR}$) microscopic technique and bulk ac/dc magnetic susceptibility measurements to study the magnetic phases of the ${\mathrm{LaCaNiReO}}_{6}$ double perovskite. As a result, we are able to discern and report ferrimagnetic ordering below ${T}_{\mathrm{C}}=102\phantom{\rule{4pt}{0ex}}\mathrm{K}$ and the formation of different magnetic domains above ${T}_{\mathrm{C}}$. Between ${T}_{\mathrm{C}}<T<270\phantom{\rule{4pt}{0ex}}\mathrm{K}$, the following two magnetic environments appear, a dense spin region and a static-dilute spin region. The paramagnetic state is obtained only above $T>270\phantom{\rule{4pt}{0ex}}\mathrm{K}$. An evolution of the interaction between Ni and Re magnetic sublattices, in this geometrically frustrated fcc perovskite structure, is revealed as a function of temperature through the critical behavior and thermal evolution of microscopic and macroscopic physical quantities.

Sequence and Characteristics of Atomic Ordering in Ni2Mn1-xCuxGa Ferromagnetic Shape Memory Alloys.

Post-quench atomic reordering processes undergone by Ni2Mn1-xCuxGa alloys have been characterized in detail. The obtained results corroborate the hypothesis that proposes an atomic ordering process additional to the B2↔L21 one, consisting of the relocation in the Mn sublattice of Cu atoms misplaced by quench in the Ni sublattice. In addition, the results suggest that the ordering of the Cu atoms and the L21 ordering can occur in different sequences depending on the starting state of order. The analysis of the saturation magnetization validates the occurrence of two types of atomic movements; the values corresponding to different post-quench stages have been compared with those calculated for different atomic configurations, supporting the relocation mechanism of Cu atoms as the most plausible mechanism. The effect of the quenching temperature on the reordering processes has been also studied, and an assessment of the degree of quenched disorder is provided, suggesting the existence of an order-disorder transition associated with Cu atoms ordering. Finally, the effect of the Cu amount has been analyzed, confirming that a greater amount of Cu intensifies the process associated to ordering of Cu atoms, which takes place even in martensite.

The impact of disorder on the 4O-martensite of Ni–Mn–Sn Heusler alloy

We have performed a quantum-mechanical study of thermodynamic, elastic, magnetic and structural properties of four different ferrimagnetic states in Ni1.9375Mn1.5625Sn0.5 martensite. They are modeled by the four-layer modulated 4O structures with Mn-excess atoms randomly distributed in Ni and Sn sublattices. The Mn atoms at the Ni sublattice turn out to be decisive for both thermodynamic and magnetic properties. A reversal of the orientation of their local magnetic moments has a huge impact on the properties of the whole system. The lowest-energy configuration exhibits anti-parallel local magnetic moments of these Mn atoms with respect to the orientation of the total magnetic moment. By testing both elastic properties and phonon modes we conclude that the lowest-energy state is mechanically stable. Vibrational properties of individual atoms are found to be very sensitive to the chemical disorder.

First‐principles insights on anion redox activity in NaxFe1/8Ni1/8Mn3/4O2: Toward efficient high‐energy cathodes for Na‐ion batteries

AbstractIn the search for high‐energy cathode materials for Na‐ion batteries (NIBs), Fe‐doped layered transition metal oxides have been recently proposed as promising systems that can ensure improved reversible capacity at high working voltage. Exploiting the anionic redox chemistry in this class of materials represents a great advance for the energy storage community, but uncontrolled oxidation process can lead to the formation of unbound molecular oxygen, with detrimental effects on overall capacity and stability upon cycling. The higher TM–O covalency provided by Fe doping seems to prevent oxygen loss and ensure full capacity recovery. Understanding anionic processes and the underlying mechanism with atomistic details can reinforce the experimental efforts and help to outline rational design strategies for novel high‐performing NIB cathodes. To this end, we present a state‐of‐the‐art first‐principles study on the P2‐type NaxTMO2 (TM = Fe, Ni, and Mn—NFNMO) oxide. We compare structural and electronic features of stoichiometric (NaxFe0.125Ni0.125Mn0.75O2) and Mn‐deficient (NaxFe0.125Ni0.125Mn0.68O2) NFNMO to identify and discuss the contribution of each element sublattice on charge compensation processes. Although Mn deficiency is predicted to increase the cathode working voltage, we find the charge compensation being mostly exerted by the Ni and Fe sublattices. Oxygen redox is unfold via the formation of superoxide species at low Na loads with a preferential breaking of more labile Ni–O bonds and binding to Fe atoms. Our calculations predict no release of molecular O2 upon desodiation, thus highlighting the key role of Fe dopant that provides a good TM–O bond strength, preventing oxygen loss while still enabling anionic redox reactions at high voltages with extra reversible capacity.

Revealing complex microstructure formation mechanisms in the Al[formula omitted]Cr[formula omitted]Fe[formula omitted]Ni[formula omitted]Ti[formula omitted] compositionally complex alloy

The complex phase evolution sequence of a promising new high temperature structural alloy with composition Al20Cr20Fe35Ni20Ti5 (at.%) has been studied in situ using an electromagnetic levitation (EML) setup combined with time-resolved high energy X-ray diffraction (XRD), as well by scanning transmission electron microscopy (STEM) observations during in situ heating. These experiments were supplemented by both scanning electron microscopy (SEM) and high resolution STEM observations of the as-cast alloy microstructure, as well as by energy dispersive X-ray spectroscopy (EDS) composition measurements. Differential scanning calorimetry (DSC) was used to identify liquidus, solidus, A2 ↔ B2, and B2 ↔ L21 transition temperatures. The results obtained by these complementary techniques indicate that the alloy forms primary dendrites of A2-structured body-centered cubic (bcc) phase initially from the melt, followed by ordered bcc of B2-structure in interdendritic regions once compositional segregation has sufficiently enriched the remaining liquid. Ordered B2 precipitates form within the primary A2-structured dendrites and the interdendritic B2 regions undergo a continuous decomposition reaction into a maze-like arrangement of A2 and B2/L21 phases below the solidus. Below approximately 1380 K, the B2 domains in both dendritic and interdendritic regions likely undergo a continuous ordering transition to the L21 phase. The experimental observations of Al20Cr20Fe35Ni20Ti5 are found to be in good agreement with CALPHAD predictions but suggest that the solubility limits of the L21-Heusler phase in the database should be relaxed to include greater Fe solubility for the Ni sublattice and to consider deviations in order parameter from stoichiometric ordering.

Semiconducting spin glass to metallic ferromagnetic state phase transition in double-substituted La1−xSrxCo1−yNiyO3−γ perovskites

A comprehensive study of the structural, magnetic, and transport properties of double-substituted ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{Co}}_{1\ensuremath{-}y}{\mathrm{Ni}}_{y}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\gamma}}$ ($0.1\ensuremath{\le}x\ensuremath{\le}0.5, 0.05\ensuremath{\le}y\ensuremath{\le}0.25$) perovskite systems was carried out. The average oxidation number of Co ions was found to be $3+$ for the most subsystems. The existence of several characteristic concentration regions for various degrees of substitution in the A (La, Sr) and B (Co, Ni) sublattices is shown. Low levels of Sr and Ni ion substitution subsystems demonstrate cluster spin-glass behavior with a semiconducting character of the conductivity and a diamagnetic low-spin (LS) ${\mathrm{Co}}^{3+}$ matrix. An increase of Ni substitution leads to the stabilization of intermediate-spin (IS) ${\mathrm{Co}}^{3+}$ ions in ${\mathrm{CoO}}_{6}$ octahedra, approaching the percolation threshold of ferromagnetic clusters. For strongly Sr-substituted subsystems an effect of stabilization of IS ${\mathrm{Co}}^{3+}$ is not observed, since the contribution of this effect is smaller than the effect of the dilution by antiferromagnetically interacting Ni ions. In this case, an increase of Ni content leads to a decrease in the magnetic ordering temperature ${T}_{\text{mo}}$ and magnetization values. For weakly Sr-substituted systems, on the contrary, it leads to their growth. Anomalies in the conductivity dependences for several subsystems are due to the thermally induced spin crossover of the part of ${\mathrm{Co}}^{3+}$ ions, first from the LS to the IS state, and then to the mixed IS/high-spin (HS) state, similar to the parent ${\mathrm{LaCoO}}_{3}$.

On the magnetic structure and magnetic behaviour of the most distorted member of the series of RNiO3 perovskites (R = Lu).

The crystal structure of LuNiO3 perovskite has been examined below RT and across TN = 125 K by neutron powder diffraction. In this temperature region (2-298 K), well below the metal-insulator transition this oxide exhibits at TMI = 599 K, this material is insulating and characterized by a partial charge disproportionation of the Ni valence. In the perovskite structure, defined in the monoclinic P21/n space group, there are two inequivalent Ni sites located in alternating octahedra of different sizes. The structural analysis with high-resolution techniques (λ = 1.594 Å) unveils a subtle increase of the charge disproportionation as temperature decreases, reaching δeff = 0.34 at 2 K. The magnetic structure has been investigated from low-T NPD patterns collected with a larger wavelength (λ = 2.52 Å). Magnetic peaks are observed below TN; they can be indexed with a propagation vector k = (½, 0, ½), as previously observed in other RNiO3 perovskites for the Ni sublattice. Among the three possible solutions for the magnetic structure, the first one is discarded since it would correspond to a full charge ordering (Ni2+ + Ni4+), with magnetic moments only on Ni2+ ions, not compatible with the structural findings assessing a partial charge disproportionation. The best agreement is found for a non-collinear model with two different moments in Ni1 and Ni2 sites, 1.4(1) μB, and m 0.7(1) μB at 2 K, the ordered magnetic moments lying on the a-c plane. This is similar to that found for YNiO3. In complement, the magnetic and thermal properties of LuNiO3 have been investigated. AC susceptibility curves exhibit a clear peak centered at TN = 125 K, corresponding to the establishment of the Ni antiferromagnetic structure. This is corroborated by DC susceptibility and specific heat measurements. Magnetization vs. field measurements confirm that the system is antiferromagnetic down to 2 K, without any further magnetic change. This linear behavior is also observed in the paramagnetic regime (T > TN).

Impact of Silica Additions on the Phase Composition and Electrical Transport Properties of Ruddlesden-Popper La2NiO4+δ Mixed Conducting Ceramics

The present work explores the possibility of incorporation of silicon into the crystal structure of Ruddlesden-Popper La2NiO4+δ mixed conducting ceramics with the aim to improve the chemical compatibility with lanthanum silicate-based solid electrolytes. Ceramics with the nominal composition La2Ni1−ySiyO4+δ (y = 0, 0.02 and 0.05) were prepared by the glycine nitrate combustion technique and sintered at 1450 °C. While minor changes in the lattice parameters of the tetragonal K2NiF4-type lattice may suggest incorporation of a small fraction of Si into the Ni sublattice, combined XRD and SEM/EDS studies indicate that this fraction is very limited (≪2 at.%, if any). Instead, additions of silica result in segregation of apatite-type La10−xSi6O26+δ and La2O3 secondary phases as confirmed experimentally and supported by the static lattice simulations. Both total electrical conductivity and oxygen-ionic transport in La2NiO4+δ ceramics are suppressed by silica additions. The preferential reactivity of silica with lanthanum oxide opens a possibility to improve the compatibility between lanthanum silicate-based solid electrolytes and La2NiO4+δ-based electrodes by appropriate surface modifications. The promising potential of this approach is supported by preliminary tests of electrodes infiltrated with lanthanum oxide.

Elemental partitions and deformation mechanisms of L12-type multicomponent intermetallics

Multicomponent high-entropy alloys (HEAs) with compositionally disordered elemental arrangement have attracted extensive attention because of their excellent mechanical properties. However, these alloys usually exhibit low strength at elevated temperatures. Recent works suggest that HEAs strengthened by L12 ordered intermetallics of the Ni3Al type possess a superior synergy of strength and ductility. The performance of such ordered-intermetallics-strengthened HEAs depends critically on the composition and deformation mechanism of the strengthening component, which will inevitably suffer partial disorder in HEAs. In this work, we study the elemental partitions and deformation mechanisms in typical multicomponent intermetallics (MCIs) based on density functional theory (DFT) calculations. Informed by experiments, systems considered in this work include L12-type (Ni,Co,Fe)3(Al,Ti,Fe) and its six derived subsystems. We first determine the site preference of different elements in MCIs using Monte-Carlo simulations with the energies obtained from DFT calculations (DFT-MC). The results confirm that Ti prefers Al sites. In contrast, most Co and Fe atoms tend to occupy Ni sublattice. With the established elemental occupations, we build quasirandom structures with partial disorders in either or both sublattices of the L12 structures. DFT results show that incorporation of Ti in the Al sublattice dominates the increase of stable planar fault energies (γSPF) in the considered MCIs. In contrast, Co in the Ni sublattice decreases the energy cost for planar fault formation. We further uncover quantitative relations between γSPF and geometrical structures as well as electronic structures in MCIs. The analytical results show that the incorporation of Ti decreases the adaptability of (Ni,Co,Fe)3(Al,Ti,Fe) both geometrically and electronically. Specifically, we propose that γSPF can be described by the ability of the alloy to accommodate planar faults, which is measured by the interlayer spacing changes between {111} planes [Δd(111)] and charge density redistribution (Δρ) at critical points (cps). We address the fundamental understandings of the deformation behavior of MCIs by pinpointing the contributions of different species to their local geometrical and electronic structures, which pave the way for rationally designing ordered-precipitate-strengthened HEAs.