Physical properties of FeSe<Subscript>0.5</Subscript>Te<Subscript>0.5</Subscript> single crystals grown under different conditions

We report on structural, magnetic, conductivity, and thermodynamic studies of FeSe_0.5Te_0.5 single crystals grown by self-flux and Bridgman methods. The lowest values of the susceptibility in thenormal state, the highest transition temperature T _c of 14.4 K, and the largest heat-capacity anomaly at T _c were obtained for pure (oxygen-free) samples. The criticalcurrent density j _c of 8.6 × 10⁴A/cm² (at 2 K) achieved in pure samples is attributed to intrinsic inhomogeneity due to disorder at the anion sites. The samples containing an impurity phase of Fe₃O₄ show increased j _c up to2.3 × 10⁵A/cm² due to additional pinning centers. The upper critical field\(H_{c2}\)of ~500 kOe is estimated from the resistivity studyin magnetic fields parallel to the c-axis using a criterion of a 50%drop of the normal state resistivity R _n . The anisotropy ofthe upper critical fieldγ _{H c2} =H ^ab _c2/H _c2 ^c reaches a value ~6 at\(T\longrightarrow T_c\). Extremely low values of the residualSommerfeld coefficient \(\gamma_r\) of about 1 mJ/mol K²,compared to the normal state Sommerfeld coefficient γ _n = 25mJ/mol K² for pure samples indicate a high volume fraction of thesuperconducting phase (up to 97%). The electronic contribution to the specific heat in thesuperconducting state is well described within a single-band BCS model with a temperature dependent gapΔ(0 K) = 27(1) K. A broad cusp-like anomaly in the electronic specific heat observed at low temperatures in samples with suppressed bulk superconductivity is ascribed to a splitting of the ground state of the Fe²⁺ ions at the 2c sites. This contribution is fully suppressed in the ordered state in samples with bulk superconductivity.     

Pressure-induced structural transformations,orbital order and antiferromagnetism in La<Subscript>0.75</Subscript>Ca<Subscript>0.25</Subscript>MnO<Subscript>3</Subscript>

High pressure evolution of structural, vibrational and magnetic properties of La_0.75Ca_0.25MnO₃ was studied by means of X-ray diffraction and Raman spectroscopy up to 39 GPa, and neutron diffraction up to 7.5 GPa. The stability of different magnetic ground states, orbital configurations and structural modifications were investigated by LDA + U electronic structure calculations. A change of octahedral tilts corresponding to the transformation of orthorhombic crystal structure from the Pnma symmetry to the Immaone occurs above P ~ 6 GPa. At the same time, the evolution of the orthorhombic lattice distortion evidences an appearance of the e _g d _{x² ? z²} orbital polarization at high pressures. The magnetic order in La_0.75Ca_0.25MnO₃ undergoes a continuous transition from the ferromagnetic 3D metallic (FM) ground state to the A-type antiferromagnetic (AFM) state of assumedly 2D pseudo-metallic character under pressure, that starts at about 1 GPa and extends possibly to 20–30 GPa.     

Specific heat of La(Fe<Subscript>0.873</Subscript>Co<Subscript>0.007</Subscript>Al<Subscript>0.12</Subscript>)<Subscript>13</Subscript> compound in antiferromagnetic and ferromagnetic states

The low-temperature specific heat C _p of La(Fe_0.873Co_0.007Al_0.12)₁₃ compound has been measured in two states: (i) antiferromagnetic (AFM) with a Néel temperature of T _N = 192 K and (ii) ferromagnetic (FM). The FM order appears at T = 4.2 K in a sample exposed to an external magnetic field with induction B _C ≥ 2.5 T and is retained for a long time in a zero field at temperatures up to T*_C = 23 K. The coefficient γ_FM in the low-temperature specific heat C = γT + βT ³ in the FM state differs quite insignificantly from that (γ_AFM) in the AFM state. Contributions to the low-temperature specific heat, which are related to a change in the elastic and magnetoelastic energy caused by magnetostrictive deformations, are considered.     

Exchange Bias in Layered GdBaCo<Subscript>2</Subscript>O<Subscript>5.5</Subscript> Cobaltite

It is established that excess oxygen content δ influences the exchange bias (EB) in layered GdBa-Co₂O_{5 + δ} cobaltite. The EB effect arises in p-type (δ > 0.5) cobaltite and disappears in n-type (δ < 0.5) cobaltite. The main parameters of EB in GdBaCo₂O_5.52(2) polycrystals are determined, including the field and temperature dependences of EB field H _EB , blocking temperature T _B , exchange coupling energy J _i of antiferromagnet–ferromagnet (AFM–FM) interface, and dimensions of FM clusters. The training effect inherent in systems with EB has been studied. The results are explained in terms of exchange interaction between the FM and AFM phases. It is assumed that the EB originates from the coexistence of Co³⁺ and Co⁴⁺ ions that leads to the formation of monodomain FM clusters in the AFM matrix of cobaltite.     

The magnetization reversal in CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/CoFe<Subscript>2</Subscript> granular systems

The temperature-dependent field cooling (FC) and zero-field cooling (ZFC) magnetizations, i.e., M _FC and M _ZFC, measured under different magnetic fields from 500 Oe to 20 kOe have been investigated on two exchange–spring CoFe₂O₄/CoFe₂ composites with different relative content of CoFe₂. Two samples exhibit different magnetization reversal behaviors. With decreasing temperature, a progressive freezing of the moments in two composites occurs at a field-dependent irreversible temperature T _irr. For the sample with less CoFe₂, the curves of ?d(M _FC ? M _ZFC)/dT versus temperature T exhibit a broad peak at an intermediate temperature T ₂ below T _irr , and the moments are suggested not to fully freeze till the lowest measuring temperature 10 K. However, for the ?d(M _FC ? M _ZFC)/dT curves of the sample with more CoFe₂, besides a broad peat at an intermediate temperature T ₂, a rapid rise around the low temperature T ₁~15 K is observed, below which the moments are suggested to fully freeze. Increase of magnetic field from 2 kOe leads to the shift of T ₂ and T _irr towards a lower temperature, and the shift of T ₂ is attributable to the moment reversal of CoFe₂O₄.

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Graphical abstract CoFe₂O₄/CoFe₂ composites with different relative content of CoFe₂ were prepared by reducing CoFe₂O₄ in H₂ for 4 h (S4H) and 8 h (S8H). The temperature-dependent FC and ZFC magnetizations, i.e., M _FC and M _ZFC, under different magnetic fields from 500 Oe to 20 kOe have been investigated. Two samples exhibit different magnetization reversal behaviors. With decreasing temperature, a progressive freezing of the moments in two composites occurs at field-dependent irreversible temperature T _irr. For the S4H sample, the curves of ?d(M _FC ? M _ZFC)/dT versus temperature T exhibit a broad and field-dependent relaxing peak at T ₂ below T _irr (figure a), and the moments were suggested not to fully freeze till the lowest measuring temperature 10 K. However, for the S8H sample, it exhibits the reentrant spin-glass state around 50 K, as evidenced by a peak in the M _FC curve (inset in figure b) and as a result of the cooperative effects of the random anisotropy of CoFe₂O₄, exchange–spring occurring at the interface of CoFe₂O₄ and CoFe₂ together with the inter-particle dipolar interaction (figure c); in ?d(M _FC ? M _ZFC)/dT curves, besides a broad relaxing peat at T ₂, a rapid rise around the low-temperature T ₁~15 K is observed, below which the moments are suggested to fully freeze. Increase of magnetic field from 2 kOe leads to the shift of T ₂ and T _irr towards a lower temperature, and the shift of T ₂ is attributable to the moment reversal of CoFe₂O₄.

     

Peculiarities of magnetic,galvanomagnetic, elastic,and magnetoelastic properties of Eu<Subscript>0.55</Subscript>Sr<Subscript>0.45</Subscript>MnO<Subscript>3</Subscript>

Magnetic, elastic, magnetoelastic, transport, and magnetotransport properties of the Eu_0.55Sr_0.45MnO₃ ceramics have been studied. A break was detected in the temperature dependence of electrical resistivity ρ(T) near the temperature of the magnetic phase transformation (41 K), with the material remaining an insulator down to the lowest measurement temperature reached (ρ=10⁶ Ω cm at 4.2 K). In the interval 4.2≤T≤50 K, the isotherms of the magnetization, volume magnetostriction, and ρ were observed to undergo jumps at the critical field H_C1, which decreases with increasing T. For 50≤T≤120 K, the jumps in the above curves persist, but the pattern of the curves changes and H_C1 grows with increasing T. The magnetoresistance Δρ/ρ = (ρ _H ?ρ_H=0)/ρ _H is positive for H<H_C1 and passes through a maximum at 41 K, where Δρ/ρ = 6%. For H>H_C1, the magnetoresistance is negative, passes through a minimum near 41 K, and reaches a colossal value of 3×10⁵ % at H=45 kOe. The volume magnetostriction is negative and attains a giant value of 4.5×10^?4atH=45 kOe. The observed properties are assigned to the existence of three phases in Eu_0.55Sr_0.45MnO₃, namely, a ferromagnetic (FM) phase, in which carriers are concentrated because of the gain in s-d exchange energy, and two antiferromagnetic (AFM) phases of the A and CE types. Their fractional volumes at low temperatures were estimated to be as follows: ～3% of the sample volume is occupied by the FM phase; ～67%, by the CE-type AFM phase; and ～30%, by the A-type AFM phase.     

Superconductivity with two-fold symmetry in topological superconductor Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript>

Topological superconductivity is the quantum condensate of paired electrons with an odd parity of the pairing function. By using a Corbino-shape like electrode configuration, we measure the c-axis resistivity of the recently discovered superconductor Sr _x Bi₂Se₃ with the magnetic field rotating within the basal planes, and find clear evidence of two-fold superconductivity. The Laue diffraction measurements on these samples show that the maximum gap direction is either parallel or perpendicular to the main crystallographic axis. This observation is consistent with the theoretical prediction and strongly suggests that Sr _x Bi₂Se₃ is a topological superconductor.     

Enhancement of the intrinsic pinning by a magnetic field in a single crystal of high-temperature superconductor TmBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>

This paper presents a comparative study of the complex permeability μ* of single crystals of hightemperature superconductors RBa₂Cu₃Oy (R = Y, Tm) as a function of the magnetic field applied along the crystallographic ab-plane. Contributions to μ* from the oscillatory motion of vortices perpendicular to layers of the crystal lattice, μ_v, and realization of the critical state along the layers are obtained. It is found that, as the temperature approaches T _c, the behavior of the field dependences of μ_v and the critical current is substantially different for the given samples. This effect is related to the manifestation of an additional unusual mechanism of intrinsic pinning, which arises when Y₃₊ is replaced with the Tm³⁺ magnetic ion. The revealed specificities of the interaction of vortices with the magnetic ion layer suggest that, most probably, they have a magnetic nature and are not related to the variation in the condensation energy in the core of the vortex.     

Spin-dimerization in rare-earth substituted La<Subscript>2</Subscript>RuO<Subscript>5</Subscript>

The Ru-Ru spin-singlet formation in La_2 ? x L n _x RuO₅ (Ln = Pr, Nd, Sm, Gd, Dy) was investigated by measurements of the specific heat and magnetic susceptibility. After subtraction of the lattice contribution from the specific heat (C _p ), similar excess entropy values were obtained for all compounds. These entropies can be explained by the formation of antiferromagnetic Ru-spin dimers at low temperatures and provide a lower estimate for the intradimer exchange strength. Pronounced changes in the transition temperatures and a broadening of the corresponding peak in C _p were observed. These changes depend on the rare-earth element and are due to local structural changes and heterogeneities caused by the substitution. The magnetic susceptibilities can be described by the sum of a rare-earth paramagnetic moment and the susceptibility of the unsubstituted La₂RuO₅. Density functional theory (DFT) calculations were performed for various compounds to investigate the origin of the magnetic transition and the relationship between structural changes and the spin-dimerization temperature. The combination of the present results with previous structural investigations supports the model of a spin-pairing of the Ru moments which occurs as a reason of the structural phase transition in La_2 ? x L n _x RuO₅.     

Dynamics of the magnetic flux component normal to the layers of Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>CaCu<Subscript>2</Subscript>O<Subscript>8</Subscript> in a tilted field

High-frequency losses in the strongly anisotropic layered superconductor Bi₂Sr₂CaCu₂O₈ are measured at 600 MHz under a magnetic field rocking about the ab plane. Anomalies in losses and hysteretic phenomena are found while performing periodic rocking, i.e., cycling the magnetic field component normal to the sample surface. Based on these observations, conclusions are drawn about the nature of magnetic-flux penetration into the superconductor. It is found that, in the range between 60 K and T _c , the dynamics of magnetic-flux vortex lines normal to the ab plane in the presence of a constant magnetic field applied parallel to this plane is governed by the critical penetration field H _c ^⊥* and the surface barrier in the presence of thermally activated vortex motion (giant flux creep). The dependences of H _c1 ^⊥* and the characteristic field of the surface barrier on the magnitude of the parallel magnetic field are measured.     

Metamagnetic effects in epitaxial BaFe<Subscript>1.8</Subscript>Cr<Subscript>0.2</Subscript>As<Subscript>2</Subscript> thin films

Epitaxial BaFe_1.8Cr_0.2As₂ thin films with the tetragonal c-axis perpendicular to the thin film surface were grown on (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 (LSAT) single crystalline substrates using pulsed laser deposition (PLD). Resistive measurements indicate the existence of two transitions at temperatures of about 80 K and 40 K. The transition at 80 K is attributed to the structural transition from the high temperature tetragonal phase to the low temperature orthorhombic phase accompanied with the magnetic transition from a paramagnetic to an antiferromagnetic state as known for doped bulk systems. Below T ≈ 40 K the magnetization curves measured perpendicularly to the orthorhombic c-axis in fields up to 9 Tesla show two inflexion points indicating metamagnetic transitions.     

Solid state synthesis of nonstoichiometric Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript>/Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> composites as visible-light photocatalyst

Nonstoichiometric Bi₂WO₆ photocatalyst with the composition of Bi_2?+?x WO_6?+?1.5x (?0.25 ≤ x ≤ 1) wa synthesized by a facile solid state reaction method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis absorption spectrum. The Bi_2.5WO_6.75 photocatalyst showed excellent visible-light-driven photocatalytic performance; nearly 100 % of RhB (10 ppm, pH?=?3?~?4) was decomposed within 25 min, which demonstrated that nonstoichiometric semiconductors could be an efficient visible-light-driven photocatalyst.     

Electrospun Dy-doped SrFe<Subscript>12</Subscript>O<Subscript>19</Subscript> nanofibers: microstructure and magnetic properties

SrDy _x Fe_12?x O₁₉ (x ≤ 0.08) nanofibers have been synthesized by the electrospinning method followed by calcinations process. The partial substitution of rare earth ions Dy³⁺ (10.5 μ _B of magnetic moments) mainly occupying 12k sublattice sites in the SrFe₁₂O₁₉ crystal structure is investigated and discussed in this work. An enhanced coercivity of 7155 Oe has been obtained when the doped content reached to 0.08 at a relative low calcination temperature of 800 °C. As a result, we believe the synthesized SrDy _x Fe_12?x O₁₉ nanofibers can potentially be useful in high-density recording media as well as permanent magnets.     

Influence of heat treatment process in In<Subscript>2</Subscript>O<Subscript>3</Subscript>-MWCNTs as photoanode in DSSCs

Indium oxide-multi-walled carbon nanotubes (In₂O₃-MWCNTs) were prepared by sol-gel method for DSSCs. The synthesis of indium oxide (In₂O₃) was carried out by dissolving indium chloride (InCl₃) in a solvent of 2-methoxyethanol. Different annealing temperatures of 400, 450, 500, 550, and 600 °C were proposed in this study. The changes in the structural properties were analyzed by means of X-ray diffraction (XRD) and atomic force microscopy (AFM) analysis. The XRD spectrum estimated the average crystallite sizes of 3 nm for each sample. AFM results indicated very rough surface area of the films where it increased linearly from 1.8 to 11 nm as the annealing temperature increases. The In₂O₃-MWCNTs-based DSSC exhibited good photovoltaic performance with power conversion efficiency (η), photocurrent density (J _sc ), open circuit voltage (V _oc ), and fill factor (FF) of 1.13 %, 5.5 mA/cm², 0.53 V, and 0.42, respectively. Even though the film annealed at 450 °C exhibited low τ _eff, it achieved the greatest D _eff of 29.67 cm² s^?1 which provides an efficient pathway for the photogenerated electrons with minimum electron recombination loss that increased the J _sc and V _oc in the DSSC. The obtained structural and electron transport analysis was proposed as a suitable benchmark for In₂O₃-MWCNTs-based dye-sensitized solar cell (DSSCs) application. Hence, this study suggests that the optimum temperature for In₂O₃-MWCNTs is at annealing temperature of 450 °C prepared via sol-gel method.     

Experimental evidence of a two-phase magnetic state in thin epitaxial films of Re<Subscript>0.6</Subscript>Ba<Subscript>0.4</Subscript>MnO<Subscript>3</Subscript> (Re = La,Pr, Nd,Gd)

Thin epitaxial films of Re_0.6Ba_0.4MnO₃ (Re = La, Pr, Nd, Gd) on (001)-oriented single crystal SrTiO₃ and ZrO₂(Y₂O₃) substrates have been prepared and studied. All films possess a cubic perovskite structure, except for the film with Re = La, which exhibited a rhombohedral distortion of the perovskite lattice. The results show evidence for the presence of two magnetic phases, ferromagnetic (FM) and antiferromagnetic (AFM), in the films studied: (i) the magnetization isotherm M(H) appears as a superposition of a linear component (characteristic of antiferromagnets) and a small spontaneous magnetization component; (ii) the magnetic moment per formula unit is significantly reduced as compared to the value expected for the complete FM or ferrimagnetic ordering; (iii) there is a difference between magnetizations of the samples cooled with and without an applied magnetic field, which is preserved in the entire range of magnetic fields studied (50 kOe); (iv) the temperature dependence of the magnetization M(T) in strong magnetic fields is close to linear (for the composition with Re = Gd, M(T) is described by a Langevin function for superparamagnets with a cluster moment of 2μ_B); and (v) the magnetization hysteresis loops of the field-cooled samples are shifted along the field axis. The exchange integral (characterizing the Mn-O-Mn coupling via the FM-AFM phase boundary) estimated from the latter shift is | J|=10^?6 eV. This value is two orders of magnitude lower than the negative exchange integral between the FM layers in ReMnO₃, which makes the presence of a transition layer at the FM-AFM phase boundary unlikely. The temperature dependences of electrical resistance and magnetoresistance exhibit maxima at the Curie temperature (T_C), where the magnetoresistance reaches a colossal value. This behavior indicates that the two-phase magnetic state is caused by a strong s-d exchange.     

An Electron Paramagnetic Resonance Study of the Orbital Ordering Compound MgTi<Subscript>2</Subscript>O<Subscript>4</Subscript>

We report the electron paramagnetic resonance (EPR) studies of MgTi₂O₄ in the 300–140 K range. Above the transition temperature T _t (~258 K), the EPR results indicate that MgTi₂O₄ is paramagnetic. The parameters of the EPR spectra show an anomalous change at T _t. The clear EPR lines can be observed in temperature between T _t and 220 K. Besides that the EPR intensity, g value, and EPR linewidth increase with decreasing temperature; in temperature range below 220 K, no clear EPR line can be detected. The EPR spectra results demonstrate that magnetic spin-singlet state and the orbital density wave of MgTi₂O₄ system are formed gradually with decreasing temperature at low temperature range.     

High-temperature complex impedance and modulus spectroscopic studies of doped Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>-BaTiO<Subscript>3</Subscript> ferroelectric ceramics

Lead-free Na_0.5Bi_0.5TiO₃ (NBT) and (1 ? x)Na_0.5Bi_0.5TiO₃ + xBaTiO₃ with x = 0.1 and 0.2 (where x = 0.1 and 0.2 are named as NBT1 and NBT2, respectively), (1 ? y)Na_0.5Bi_0.5TiO₃ + yBa_0.925Nd_0.05TiO₃ with y = 0.1 and 0.2 (where y = 0.1 and 0.2 are named as NBT3 and NBT4, respectively)-based relaxor ferroelectric ceramics were prepared using the sol-gel method. The crystal structure was investigated by X-ray diffraction (XRD) at room temperature (RT). The XRD patterns confirmed the presence of the rhombohedral phase in all the samples. The electrical properties of the present NBT-based samples were investigated by complex impedance and the modulus spectroscopy technique in the temperature range of RT–600 °C. The AC conductivity was found to increase with the substitution of Ba²⁺ ions to the NBT sample whereas it significantly decreased with the addition of Nd³⁺ ions. The more anion vacancies in Ba-added samples and the lower anion vacancies in Nd-added samples were found to be responsible for higher and lower conductivities, respectively.     

Photoionization of the Xe atom and Xe@C<Subscript>60</Subscript> molecule

Photoionization of the Xe atom and Xe@C₆₀ molecule have been studied usingthe random phase approximation with exchange (RPAE) method. The Xe atom was described byrelaxed orbitals including overlap integrals. The C₆₀ fullerene has beenrepresented by an attractive short range spherical well with potentialV(r), given byV(r) =  ?V ₀ forr _i  < r < r _o ,otherwise V(r) = 0 wherer _i andr _o are respectively, the inner and outerradii of the spherical shell. The time independent Schrödinger equation was solved usingboth regular and irregular solutions and the continuous boundary conditions atr _i andr _o . The results demonstrate improvementto previous calculations for both the Xe atom and Xe@C₆₀ molecule and comparevery well with the recent experimental data.     

High-resolution spectroscopy of HoFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> crystal: a study of phase transitions

The transmission spectra of HoFe₃(BO₃) multiferroic single crystals are studied by optical Fourier-transform spectroscopy at temperatures of 1.7–423 K in polarized light in the spectral range 500–10 000 cm^–1 with a resolution up to 0.1 cm^–1. A new first-order structural phase transition close to the second-order transition is recorded at T_c = 360 K by the appearance of a new phonon mode at 976 cm^–1. The reasons for considerable differences in T_c for different samples of holmium ferroborate are discussed. By temperature variations in the spectra of the f–f transitions in the Ho³⁺ ion, we studied two magnetic phase transitions, namely, magnetic ordering into an easy-plane structure as a second-order phase transition at T_N = 39 K and spin reorientation from the ab plane to the c axis as a first-order phase transition at T_SR = 4.7 ± 0.2 K. It is shown that erbium impurity in a concentration of 1 at % decreases the spin-reorientation transition temperature to T_SR = 4.0 K.     

Substitution effects on the bulk and surface properties of (Li,Ni)Mn<Subscript>2</Subscript>O<Subscript>4</Subscript>

Manganese oxides of spinel structure, LiMn₂O₄, Li_1-x Ni _x Mn₂O₄ (0.25 ≤ x≤ 0.75), and NiMn₂O₄, were studied by EDS, XRD, SEM, magnetic (M-H, M-T), and XPS measurements. The samples were synthesized by an ultrasound-assisted sol-gel method. EDS analysis showed good agreement with the formulations of the oxides. XRD and Rietveld refinement of X-ray data indicate that all samples crystallize in the Fd3m space group characteristic of the cubic spinel structure. The a-cell parameter ranges from a = 8.2276 Å (x = 0) to a = 8.3980 Å (x = 1). SEM results showed particle agglomerates ranging in size from 2.3 μm (x = 0) down to 0.8 μm (x = 1). Hysteresis magnetization vs. applied field curves in the 5–300K range was recorded. ZFC-FC measurements indicate the presence of two magnetic paramagnetic-ferrimagnetic transitions. The experimental Curie constant was found to vary from 5 to 7.1 cm³ K mol^?1 for the range of compositions studied (0 ≤ x ≤ 1). XPS studies of these oxides revealed the presence of Ni²⁺, Mn³⁺, and Mn⁴⁺. The experimental Ni/Mn atomic ratios obtained by XPS were in good agreement with the nominal values. A linear relationship of the average oxidation state of Mn with Ni content was observed. The oxide’s cation distributions as a function of Ni content from x = 0 ?Li⁺[Mn³⁺Mn⁴⁺]O₄ to x = 1 \( {\mathrm{Ni}}_{0.35}^{2+}{\mathrm{Mn}}_{0.65}^{3+}\left[{\mathrm{Ni}}_{0.65}^{2+}\right.\left.{\mathrm{Mn}}_{1.35}^{3+}\right]{\mathrm{O}}_4 \) were proposed.