Ion Occupancy Research Articles

Lone-pair electron effect induced a rapid photorefractive response in site-controlled LiNbO3:Bi,M (M = Zn, In, Zr) crystals

As a promising candidate material for holographic 3D displays, lithium niobate (LN) is limited by its low photorefractive (PR) response. Recently, it has been reported that bismuth dopants significantly improve the PR properties of LN crystals. However, the mechanism of photorefraction enhancement and whether the performance can be further optimized are not clear. In this paper, we demonstrate that Zn2+, In3+, and Zr4+ co-dopants can enhance the photorefraction of LiNbO3:Bi crystals. In particular, the PR sensitivity of LN:Bi,Zn8.0 crystal reaches 11.7 cm/J at 488 nm, with a diffraction efficiency of 16.67% and a response time of 290 ms. We propose that Bi ions occupy Nb sites, forming BiNb2−/BiNb0 in LN:Bi,Zn crystals, while still occupying Li sites, forming BiLi2+/BiLi4+ in LN:Bi,Zr crystals, when the Zn/Zr concentration exceeds the doping threshold. These occupying models are confirmed by the atomic resolution of scanning transmission electron microscopy. Additionally, we find that the lone-pair electron effect of Bi is pronounced when Bi3+ ions occupy Nb sites, forming the most highly efficient PR centers, which induce an outstanding PR response in LN:Bi,Zn8.0 crystal. Our results clarify the occupation of bismuth ions in Zn, In, or Zr co-doped LiNbO3:Bi and confirm that the PR performance can be further improved by site control.

Rheological and the Fresh State Properties of Alkali-Activated Mortars by Blast Furnace Slag

The fresh and rheological properties of alkali mortars activated by blast furnace slag (BFS) were investigated. Consistency tests, squeeze flow, dropping ball, mass density in the hardened state, incorporated air, and water retention were performed. Mortars were produced with the ratio 1:2:0.45 (binder:sand:water), using not only ordinary Portland cement for control but also BFS, varying the sodium content of the activated alkali mortars from 2.5 to 15%. The results obtained permitted understanding that mortars containing 2.5 to 7.5% sodium present a rheological behavior similar to cementitious mortars by the Bingham model. In turn, the activated alkali mortars containing 10 to 15% sodium showed a very significant change in the properties of dynamic viscosity, which is associated with a change in the type of model, starting to behave similar to the Herschel–Bulkley model. Evaluating the properties of incorporated air and water retention, it appears that mortars containing 12.5% and 15% sodium do not have compatible properties, which is related to the occupation of sodium ions in the interstices of the material. Thus, it is concluded that the techniques used were consistent in the rheological characterization of activated alkali mortars.

Defects & Luminescence of Lu3Al5O12 Phosphor Doped with Na Ion

A systematic first-principles study on occupation of Na ions in Lu3Al5O12 (LuAG) lattice and effect on oxygen vacancies, dominant intrinsic antisite defect (AD) was performed. We found that the Na ...

Implication of Lithium Excess Induced Structure and Electrochemical Behavior Changes of LiNi0.5Mn1.5O4 Spinel

Cubic spinel LiNi0.5Mn1.5O4 is one of the most promising cathode materials for high energy density lithium ion batteries because of its higher voltage plateau at around 4.7 V vs Li+/Li. In this paper, LiNi0.5Mn1.5O4 spinels are synthesized with different lithium excess, and their composition, structure, morphology and electrochemical behavior are measured and compared. The results show that all samples have an ordered cubic spinel structure with Ni/Mn ordering in the octahedral sites, and the change of lithium excess can induce variations in phase composition and purity, Mn3+ amount, cation mixing and electrochemical behavior of the prepared LiNi0.5Mn1.5O4. Even with the least amount of Mn3+ and a higher amount of impurity, the sample with the least occupation of transition metal ions in the tetrahedral Li sites gives the best rate performance, justifying that the occupation of transition metal ions in the tetrahedral Li sites play a critical role in affecting the kinetics of lithium ion extraction/insertion for LiNi0.5Mn1.5O4 spinel.

Solution combustion synthesis and luminescence dynamics of CaTiO3: Eu3+, Y3+ nanophosphors

Perovskite titanate nanophosphors, Ca1-x-yYxTiO3:yEu3+ have been synthesized through solution combustion synthesis using metal-citrate complexation method. The optimum substitution of Y3+ ions in Ca0·93TiO3:0.07Eu3+ phosphor enhances the intensity of luminescence 10 times along with the realization of the color purity of 91% and the luminescence life time value to 1.3 ms. X-ray Photoelectron Spectroscopy studies confirm the 3+ oxidation state of yttrium and europium ions and the occupancy of these ions at Ca2+ sites. The sole presence of Raman modes representing the orthorhombic structure and the TEM analysis reveal the high degree of crystallinity of phosphors. The substitution of rare earth ions causes the distortion of local crystal structure symmetry by the tilting of TiO6 octahedra and this results in the shift of Raman modes of CaTiO3. The single exponential nature of luminescence decay curves suggests the occupancy of substituent ions at the Ca2+ sites. Judd- Ofelt analysis gives the quantum efficiency as 81.6% for the phosphor with optimum dopant concentration.

Insight into Ion Diffusion Dynamics/Mechanisms and Electronic Structure of Highly Conductive Sodium-Rich Na3+xLaxZr2-xSi2PO12 (0 ≤ x ≤ 0.5) Solid-State Electrolytes.

Solid-state electrolytes (SSEs) have attracted considerable attention as an alternative for liquid electrolytes to improve safety and durability. Sodium Super Ionic CONductor (NASICON)-type SSEs, typically Na3Zr2Si2PO12, have shown great promise because of their high ionic conductivity and low thermal expansivity. Doping La into the NASICON structure can further elevate the ionic conductivity by an order of magnitude to several mS/cm. However, the underlying mechanism of ionic transportation enhancement has not yet been fully disclosed. Herein, we fabricate a series of Na3+xLaxZr2-xSi2PO12 (0 ≤ x ≤ 0.5) SSEs. The electronic and local structures of constituent elements are studied via synchrotron-based X-ray absorption spectroscopy, and the ionic dynamics and Na-ion conduction mechanism are investigated by solid-state nuclear magnetic resonance spectroscopy. The results prove that La3+ ions exist in the form of phosphate impurities such as Na3La(PO4)2 instead of occupying the Zr4+ site. As a result, the increased Si/P ratio in the NASICON phase, accompanied by an increase in the sodium ion occupancy, makes a major contribution to the enhancement of ionic conductivity. The spin-lattice relaxation time study confirms the accelerated Na+ motions in the altered NASICON phase. Modifications on the Si/P composition can be a promising strategy to enhance the ionic conductivity of NASICON.

Magnetic properties of Ni5Sn(O2BO3)2 ludwigite

The magnetic properties of site-disordered ${\mathrm{Ni}}_{5}\mathrm{Sn}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$ ludwigite have carefully been studied using local probes and bulk experimental methods in temperatures down to 1.6 K and magnetic fields up to 9 T. Our results have clearly shown the role of the effect of order/disorder site occupancy in these complex compounds with spin moments $S=1$. Different from most ludwigites, site-disordered ${\mathrm{Ni}}_{5}\mathrm{Sn}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$ ludwigite has shown three magnetic transitions at 80, 50, and 5 K. Local probes ($^{119}\mathrm{Sn}$ M\"ossbauer and muon spin spectroscopy) have indicated a partial long-range magnetic order with onsets at 80 and 50 K with predominant ferromagnetic interactions at 80 K and antiferromagnetic ones at 50 K. At lower temperatures, a partial spin-glass-like freezing of the moments has been developed concomitantly with fraction of the moments ordered at higher temperatures, a spin-glass-like and long-range magnetic order coexist and a spontaneous exchange bias effect has been observed. Applied magnetic fields have gradually reduced magnetic frustration, leading to a magnetically ordered state of the complete structure at 51 K under 9 T. The absence of double-exchange interactions in order/disorder ${\mathrm{Ni}}_{5}\mathrm{Sn}{({\mathrm{O}}_{2}{\mathrm{BO}}_{3})}_{2}$ ludwigites shows how the magnetic interactions that compete as direct exchange and double exchange are modified by the site occupancy of nonmagnetic Sn ions. Features as a third magnetic transition, the appearance of spontaneous exchange bias, and the enhancement of the coercive field at low temperatures were not found in the site-ordered isomer compound.

A comparative study of spinel ZnFe2O4 ferrites obtained via a hydrothermal and a ceramic route: Structural and magnetic properties

The spinel ZnFe2O4 specimens were obtained via a hydrothermal and a ceramic method, respectively, and their structural and magnetic properties were comparatively studied. It was found that all the specimens exhibited a single-phase and mixed spinel structure. The magnetism of specimens synthesized via the hydrothermal method is obviously better than that of specimen prepared via the ceramic method. This can be ascribed to the different occupancy of Fe ions resulted from the loss of Zn during the hydrothermal process.

Investigation of the Inactivation of HERG using Molecular Dynamics Simulations of New cryo-EM Structures

The human ether á-go-go related gene (hERG) encodes the delayed rectifier potassium channel (Kv11.1), best known for mediation of the repolarising current in the cardiac action potential. Loss of function of hERG can lead to long QT-syndrome which causes cardiac arrhythmias and sudden cardiac arrest. hERG is susceptible to a wide range of drugs which can lead to drug induced long QT-syndrome. Here, the recent cryo-EM structure of hERG in an activated state, together with newly-solved structures that are open or inactivated serve as the basis to investigate the structural determinants of hERG inactivation. We used molecular dynamics flexible fitting to refine and relax these new structures in micelles consisting of detergents, lipids and cholesterol. A combination of long simulations and libraries of short simulations were performed with a variety of ion concentrations to study different conformational states. These simulations highlighted the amino acids important for maintaining each state of the selectivity filter and therefore may be involved in hERG inactivation. Furthermore, we have used replica exchange with solute tempering to enhance sampling of the exchange of ions in the hERG selectivity filter. We observe correlations between channel conformation and ion occupancy that shed light on the coupling of ions to inactivation. Together with mutagenesis experiments, these simulations provide molecular-level understanding of hERG inactivation, with considerable clinical and pharmacological potential.

Single-crystal neutron and X-ray diffraction study of garnet-type solid-state electrolyte Li6La3ZrTaO12: an in situ temperature-dependence investigation (2.5 ≤ T ≤ 873 K)

Large single crystals of garnet-type Li6La3ZrTaO12 (LLZTO) were grown by the Czochralski method and analysed using neutron diffraction between 2.5 and 873 K in order to fully characterize the Li atom distribution, and possible Li ion mobility in this class of potential candidates for solid-state electrolyte battery material. LLZTO retains its cubic symmetry (space group Ia 3 d) over the complete temperature range. When compared to other sites, the octahedral sites behave as the most rigid unit and show the smallest increase in atomic displacement parameters and bond length. The La and Li sites show similar thermal expansion in their bond lengths with temperature, and the anisotropic and equivalent atomic displacement parameters exhibit a distinctly larger increase at temperatures above 400 K. Detailed inspection of nuclear densities at the Li1 site reveal a small but significant displacement from the 24d position to the typical 96h position, which cannot, however, be resolved from the single-crystal X-ray diffraction data. The site occupation of LiI ions on Li1 and Li2 sites remains constant, so there is no change in site occupation with temperature.

Thermodynamics of ion binding and occupancy in potassium channels.

Potassium channels modulate various cellular functions through efficient and selective conduction of K+ ions. The mechanism of ion conduction in potassium channels has recently emerged as a topic of debate. Crystal structures of potassium channels show four K+ ions bound to adjacent binding sites in the selectivity filter, while chemical intuition and molecular modeling suggest that the direct ion contacts are unstable. Molecular dynamics (MD) simulations have been instrumental in the study of conduction and gating mechanisms of ion channels. Based on MD simulations, two hypotheses have been proposed, in which the four-ion configuration is an artifact due to either averaged structures or low temperature in crystallographic experiments. The two hypotheses have been supported or challenged by different experiments. Here, MD simulations with polarizable force fields validated by ab initio calculations were used to investigate the ion binding thermodynamics. Contrary to previous beliefs, the four-ion configuration was predicted to be thermodynamically stable after accounting for the complex electrostatic interactions and dielectric screening. Polarization plays a critical role in the thermodynamic stabilities. As a result, the ion conduction likely operates through a simple single-vacancy and water-free mechanism. The simulations explained crystal structures, ion binding experiments and recent controversial mutagenesis experiments. This work provides a clear view of the mechanism underlying the efficient ion conduction and demonstrates the importance of polarization in ion channel simulations.

Investigation on the site preferences & magnetic properties of Co-doped SrAl4Fe8O19 hexaferrite

The present work describes the structural and magnetic properties of partially Co substituted SrAl4CoxFe8-xO19 (0.0≤ x ≤ 0.6) ferrites. Single-phase strontium hexaferrite (p63/mmc) was synthesized by the sol-gel auto combustion method. The structural studies were carried out by the Rietveld analysis to get the information about the substituted sites of transition metal ions, bond length, and bond angle. Types of the bond were also explored through FTIR. EDX elemental analysis and mapping had also verified the presence of single-phase strontium hexaferrite. The effect of Co ion substitution on the magnetic properties was investigated with the help of a magnetic property measurement system (MPMS). The relationship between the occupancy of transition metal ions over the five sub-lattice sites was analyzed. The magneto-crystalline anisotropy was analyzed from the “Law of Approach to Saturation magnetization (Ms)” method. The oxidation state of the Co ion was also examined by the XAS spectra. The substitution of Co+3 enhanced the magnetization and permeability of the ferrites. Results indicated the significant dependency of Co+3 ion on the magnetic properties of strontium hexaferrite.

Investigation the effect of sodium carboxymethylcellulose as polycounterion on cetirizine hydrochloride–sodium dodecyl sulphate mixed micelle

The aim of this research was to investigate the binding properties of sodium carboxymethylcellulose (NaCMCu) as polycounterions on mixed micelles of drug surfactants. Mixed micellization behavior of cetirizine hydrochloride (CTZ) and sodium dodecyl sulphate (SDS) was investigated in the absence and presence of NaCMCu using electrical conductivity, surface tension, fluorescence measurements, dynamic light scattering and UV measurements. The critical micelle concentration (CMC) in the aqueous and NaCMCu medium of CTZ + SDS mixed micelle was lower than the single micelle of CTZ and SDS. The presence of electrostatic interaction between NaCMCu and CTZ + SDS could increase the stability of mixed micelle from αSDS 1.0–0.0. The results showed that CTZ + SDS monomers could bind to the NaCMCu chains and form free mixed micelles in the solution, whereas no SDS / NaCMCu micelle-like complexes were found due to repulsive interaction. NaCMCu significantly decreased the CMC of CTZ. The values of counterion binding (B) from Corrin–Harkins approach and binding constant (Kb) indicated that the CTZ micelles bound to electrostatic interaction by –COO¯ ions of NaCMCu. UV absorbance data given a significant parameter, mean ion occupancy per micelle (i0) which estimated the occupancy per micelle of polycounterions for αSDS 1.0–0.0. However, the turbidity data and micellar size showed that the amount of NaCMCu increased, and the mixed micellar size also increased. Eventually, this system demonstrated that polyelectrolyte was used as an organic counterion to improve the micellar properties of amphiphilic drugs for the formulation of pharmaceutical medicinal products.

A New Class of Superionic Solid-State Lithium-Ion Conductors: Lithium-Phosphido Silicates, Germanates, and Aluminates

Superionic conductors as a solid-state electrolyte materials are essential for use for all-solid-state lithium ion batteries. Whereas intensive research on oxide and sulfide based lithium ion conductors resulted in optimized materials which reach ionic conductivities up to 25 mScm-1 other compound classes are disregarded. A design principle for fabricating new superionic conductors follows the ideas of increasing the carrier densities, changing the diffusion pathways of the mobile species, creating vacancies or increasing structural defects, and including anions that are more polarizable. For example to increase the carrier density, an effective way is especially the aliovalent substitution of cations: for example, in Li3PS4 making a formal substitution from “P5+” to “Ge4+” arises in Li3.25Ge0.25P0.75S4 with a four times higher ionic conductivity.We propose here phosphide-based materials as ionic conductors that result in principle from the aliovalent substitution of [TtS4]4- tetrahedra, which are an important key building block in sulfide-based electrolytes, by [TtP4]8- leading to the analogous complex anions based on phosphorus (Tt = tetrel element = Group-14 element). The resulting higher charge of the [TtP4]8- tetrahedra allows for twice the number of lithium ions per formula unit for charge compensation if compared to [TtS4]4- and in addition, the more negatively charged P3- is more polarizable than S2-. In this context we discovered for example Li8SiP4,[1] β-Li8GeP4,[2] and Li14SiP6 [3] with conductivities up to 1.1 mScm-1 . In addition we recently succeded to synthesize the lithium richest representative, obtained by formal aliovalent substitution of “Tt 4+” by “Al3+” and formation of in Li9AlP4.[4] The insertion of Al3+ leads to formally nine-fold negatively charged [AlP4]9- tetrahedra, resulting in an even higher lithium density per formula unit and a change in spatial extent of the diffusion pathways. This first representative of a novel compound class of lithium phosphidoaluminates has as an undoped material a remarkable fast ionic conductivity of ~ 3 mS cm-1 and a low activation energy of ~ 29 kJ mol−1 as determined by impedance spectroscopy. Temperature-dependent 7Li NMR spectroscopy supports the fast lithium motion. In addition, Li9AlP4 combines a very high lithium content with a very low theoretical density of 1.703 g·cm-3.In this paper we give an overview on the recent development in this material class. All crystalline materials are readily obtained as single phase materials by ball mill synthesis from the elements followed by moderate thermal treatment of the mixtures. In all cases the atomic structures are characterized by X-ray diffraction methods. The lithium-ion mobility was investigated by temperature-dependent nuclear magnetic resonance and electrochemical impedance spectroscopy revealing low activation energies for lithium hopping. In some cases lithium diffusion pathways via both, tetrahedral and octahedral voids are analyzed by temperature-dependent powder neutron diffraction measurements in combination with maximum entropy method (MEM) and DFT calculations. The role of lithium ion occupation in the various tetrahedral and octahedral sites that occur in those compounds is highlighted.

Cu/S-Occupation Bifunctional Oxygen Catalysts for Advanced Rechargeable Zinc-Air Batteries.

The design and synthesis of low-cost and highly efficient bifunctional catalysts is an inevitable path for rechargeable zinc-air batteries (rZABs). In this work, double-carbon co-supported Co-based oxide with the Cu and S substitutions are synthesized by a one-step hydrothermal method and formed a unique honeycomb structure. As expected, the (Cu, Co)3OS3@CNT-C3N4 exhibits high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity with low overpotential (0.86 V), high power density (215 mW cm-2), and long-term discharge stability (115 h). The (Cu, Co)3OS3@CNT-C3N4-based rZAB also shows a stronger charge-discharge durability with a very low voltage gap of merely 0.5 V than that of Pt/C+RuO2. The high catalytic performances are attributed to these following reasons: (i) the porous morphology and hierarchical structure with plentiful "catalytic buffer", which accelerates the mass transfer; (ii) a high-speed electronic transmission network established by C3N4 and carbon nanotube (CNT), enhancing the conductivity; (iii) the strong synergistic effect between (Cu, Co)3OS3@CNT and C3N4, which improves the kinetics of ORR/OER; and (iv) the controllable occupation of Cu ions and S ions, which effectively regulates the CoO6 surface and increases the active site density. This work not only offers a promising ORR/OER electrode for rZAB but also provides a new pathway to understand the improvement mechanism for catalysts by the bi-ion substitutions.

High Pressure Effect on Structural and Electrochemical Properties of Anionic Redox-Based Lithium Transition Metal Oxides

Summary The richness of anionic redox chemistry in the solid state offers new opportunities and a possible paradigm shift in energy storage. The excess capacity that goes beyond conventional theoretical values is attributed to the anionic redox in Li-rich transition metal oxide cathodes for Li-ion batteries. Their electrochemical behavior is thermodynamically determined by structural evolution. To better understand the electrochemical dependence on structural factors, we have induced structural modifications in pristine and electrochemically activated Li1.144Ni0.136Co0.136Mn0.544O2 through high-pressure treatment. A unique cyclical change of structural reordering is observed in the anionic redox-activated material during operando pressure sweep, characterized by a periodic evolution of superlattice peak intensity in synchrotron X-ray diffraction patterns. During the structural reordering period, the bulk compressibility of the material decreases, even becoming negative. These insights elucidate the structural flexibility and metastability of anionic redox-based materials, which can undergo large compressions and structural modifications while delivering good electrochemical properties.

Immobilization of simulated An3+ into synthetic Gd2Zr2O7 ceramic by SPS without occupation or valence design

To simplify the immobilized process of nuclear waste, synthetic Gd2Zr2O7 ceramic was employed to immobilize simulated An3+ (Nd3+) by spark plasma sintering (SPS) without any ion occupation or valence design. Sintering and characterization of immobilized simulated An3+ with various doping amounts were carried out. The effects of Nd2O3 content on the phase composition, active modes, micro-graph and density of the sintered ceramics were investigated. When the Nd2O3 doped amount reached up to 50 mol%, the raw peak of Nd2O3 existed. The sintered ceramics kept a single fluorite phase when Nd2O3 solubility achieved to 40 mol%. The sintered ceramics presented a well crystalline phase and the elements distributed evenly. In addition, as the Nd2O3 doped amount increase, the density and Vickers hardness values of Nd2O3 doped sample decrease.

Lattice dynamics and high‐pressure properties of K‐ionic conducting system KNbTeO6

AbstractIn the present work, we report results of high‐pressure Raman scattering spectroscopy, on the ionic conducting system KNbTeO6, as well as lattice dynamics calculations for this compound. From lattice dynamics calculation, we were able to do a definite assignment of modes for this system taking into account the disorder caused by random K occupation and shared occupation of Nb and Te ions. On the basis of the theoretical results, we discuss the changes observed in the high‐pressure Raman spectra. We report a transformation occurring around 4.7 GPa, attributed it to a structural phase transition. The Raman spectra during the decompression process reveals that all changes undergone by the structure are reversible, and the Raman spectrum recovers its original signature.

Heuristic solution for achieving long-term cycle stability for Ni-rich layered cathodes at full depth of discharge

The demand for energy sources with high energy densities continues to push the limits of Ni-rich layered oxides, which are currently the most promising cathode materials in automobile batteries. Although most current research is focused on extending battery life using Ni-rich layered cathodes, long-term cycling stability using a full cell is yet to be demonstrated. Here, we introduce Li[Ni0.90Co0.09Ta0.01]O2, which exhibits 90% capacity retention after 2,000 cycles at full depth of discharge (DOD) and a cathode energy density >850 Wh kg−1. In contrast, the currently most sought-after Li[Ni0.90Co0.09Al0.01]O2 cathode loses ~40% of its initial capacity within 500 cycles at full DOD. Cycling stability is achieved by radially aligned primary particles with [003] crystallographic texture that effectively dissipate the internal strain occurring in the deeply charged state, while the substitution of Ni3+ with higher valence ions induces ordered occupation of Ni ions in the Li slab and stabilizes the delithiated structure. Nickel-rich layered oxide cathodes are at the forefront of the development of automobile batteries. The authors report an atomic and microstructural engineering design for a Li[Ni0.90Co0.09Ta0.01]O2 cathode that exhibits outstanding long-term cyclability and high energy at full depth of discharge in full cells.

Understanding the relationship between the local crystal structure and the ferrimagnetic ordering of CoxMn3-xO4 (x = 0–0.5) solid solutions

The local crystal structure alterations in the tetrahedral positions of the hausmannite Mn3O4 structure by Co2+ ions and its consequence on the magnetic ordering are studied in detail. The cation composition, bond distance and bond angle of the CoxMn3-xO4 series (x = 0.0. 0.1, 0.3 and 0.5) is determined by XRD Rietveld refinement. The charge state of the elements Co, Mn and O are investigated using XPS measurements, which confirm the bivalent cobalt ion occupation in the tetrahedral lattice. Considerable reduction in tetrahedral and axial octahedral bonds with the introduction of Co2+ ions dramatically increased the Curie temperature (TC) from 43 K (Mn3O4) to 62 K (Co0.5Mn2.5O4). The Lotgering-Srinivasan-Seehra model is employed to study the canted spin arrangement and the exchange interactions of Co0.5Mn2.5O4. The presence of cluster glass transition at TP = 42 K in Co0.3Mn2.7O4 is well-established through the AC susceptibility measurements and it is further substantiated by Vogel-Fulcher law and dynamic scaling power law. The origin of the cluster glass state is confirmed by the calculated strong geometric frustration factor (f = 19.5), due to the inhomogeneous distribution of cobalt ions in the intermediate concentrations. Field cooled isothermal magnetic measurements corroborated the exchange bias phenomenon in the Co0.3Mn2.7O4 sample, because of the interaction between ferrimagnetic-cluster glass phases occurring below the spin freezing temperature TP.