A Fe Mössbauer study of charge ordering and phase separation in the rare-earth manganates, Nd0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3

Mössbauer studies of 2% ⁵⁷Fe-doped Nd_0.5Ca_0.5MnO₃ and Nd_0.5Sr_0.5MnO₃ have been carried out over the 4.2-300 K range after ensuring that such doping does not change their basic properties. The charge-ordering transition in these manganates is marked by abrupt changes in the quadrupole splitting. In the case of Nd_0.5Ca_0.5MnO₃, two phases manifest themselves on cooling below the charge-ordering transition temperature. The evolution of the spectra as a function of temperature shows that long-range magnetic order does not occur sharply. The observed evolution with temperature is different in the two materials studied. In Nd_0.5Ca_0.5Mn_0.98⁵⁷Fe_0.02O₃, it resembles that of a disordered magnetic material, whereas the temperature dependence of line shape of Nd_0.5Sr_0.5Mn_0.98⁵⁷Fe_0.02O₃ is typical of a superparamagnetically relaxed magnetic system. Although both the manganates show well-resolved magnetic hyperfine spectra at 4.2 K, the lines are slightly broad indicating possible coexistence of phases at low temperatures. A weak paramagnetic signal is also seen in the spectra of both the manganates at 4.2 K.     

Magnetic properties of La0.5−xLnxSr0.5MnO3 (Ln=Pr, Nd, Gd and Y)

Magnetic and electron transport properties of four series of manganates of the composition La_0.5−xLn_xSr_0.5MnO₃ (Ln=Pr, Nd, Gd and Y) have been investigated to examine how the ferromagnetic metallic nature of the parent La compound changes over to antiferromagnetic insulating behavior, with change in Ln and x due to the associated changes in the A-site cation radius as well as the size disorder. When Ln=Pr and Nd, there is a transition from the tetragonal I4/mcm structure to the orthorhombic Immm and Imma structures at x=0.2 and 0.35, respectively. There is a gradual evolution of the properties from those of La_0.5Sr_0.5MnO₃ to those of Pr_0.5Sr_0.5MnO₃ or Nd_0.5Sr_0.5MnO₃ with increase in x. Thus, when x>0.2 and >0.35, respectively, the Pr- and Nd-substituted manganates show ferromagnetic transitions followed by antiferromagnetic transitions at low temperatures, with the ferromagnetic T_C decreasing with increasing x. The Gd and Y series of compounds are all orthorhombic and show a decrease in T_C with the increase in x, the ferromagnetism disappearing at high x. At a value of x corresponding to the A-site cation radius of Pr_0.5Sr_0.5MnO₃, the Gd and Y series of compounds exhibit ferromagnetism in the 250-300 K region and undergo an antiferromagnetic transition on cooling. The T_C−T_N gap is sensitive to the disorder arising from the size mismatch.     

Approaching compositional limits of perovskite – type oxides and oxynitrides by synthesis of Mg0.25Ca0.65Y0.1Ti(O,N)3, Ca1–xYxZr(O,N)3 (0.1 ≤ x ≤ 0.4), and Sr1–xLaxZr(O,N)3 (0.1 ≤ x ≤ 0.4)

Partial substitution of cations and anions in perovskite-type materials is a powerful way to tune the desired properties. The systematic variation of the cations size, the partial exchange of O²⁻ for N³⁻ and their effect on the size of the optical band gap and the thermal stability was investigated here. The anionic substitution resulted in the formation of the orthorhombic perovskite-type oxynitrides Mg_0.25Ca_0.65Y_0.1Ti(O,N)₃, Ca_1-xY_xZr(O,N)₃, and Sr_1–xLa_xZr(O,N)₃. A two-step synthesis protocol was applied: i) (nano-crystalline) oxide precursors were synthesized by a Pechini method followed by ii) ammonolysis in flowing NH₃ at T = 773 K (Ti) and T = 1273 K (Zr), respectively. High-temperature synthesis of such oxide precursors by solid–state reaction generally resulted in phase separation of the different A-site cations. Changes of the crystal structures were investigated by Rietveld refinements of the powder XRD data, thermal stability by DSC/TG measurements in oxygen atmosphere, oxygen and nitrogen contents by O/N analysis using hot gas extraction technique, and optical band gaps by photoluminescence spectroscopy. By moving from Mg_0.25Ca_0.65Y_0.1Ti(O,N)₃ via Ca_1–xY_xZr(O,N)₃ to Sr_1–xLa_xZr(O,N)₃, the degree of tilting of the octahedral network is reduced, as observed by an increase in the B–X–B angles caused by the simultaneously increasing effective ionic radius of the A-site cation(s). In general, increasing substitution levels on the A-site (Y³⁺ and La³⁺) are accompanied by an enhanced replacement of O²⁻ by N³⁻. In all three systems, this anionic substitution resulted in a reduction of the optical band gap by approximately 1 eV (Ti) and up to 2.1 eV (Zr) compared to the respective oxides. For Mg_0.25Ca_0.65Y_0.1Ti(O,N)₃ an optical band gap of 2.2 eV was observed, appropriate for a solar water splitting photocatalyst. The Zr-based oxynitrides required a by a factor of 2 higher nitrogen contents to significantly reduce the optical band gap and the measured values of 2.9 eV–3.2 eV are larger compared to the Ti-based oxynitride. Bulk thermal stability was revealed up to T = 881 K. In general, the thermal stability decreased with increasing substitution levels due to an increasing deviation from the ideal anionic composition as demonstrated by O/N analysis.     

Evolution of magnetic state in the La1−xCaxMnO3−γ (x=0.30, 0.50) manganites depending on the oxygen content

The crystal structure, magnetic and electrical properties of the La_1−xCa_xMnO_3−γ (x=0.30, 0.50; 0?γ?0.50) oxygen-deficient manganites have been studied. It is found that the compounds La_0.70Ca_0.30MnO_3−γ possess a long-range ferromagnetic order up to γ=0.06 and a cluster spin glass behavior at 0.06<γ?0.20. Antiferromagnetic state of La_0.50Ca_0.50MnO_3−γ (γ=0) composition transforms into inhomogeneous ferromagnetic one at γ=0.04. The system converts into cluster spin glass state at γ=0.10. As oxygen deficit reaches the value γ=0.25, a new type of ferromagnetic phase appears. The fraction of this ferromagnetic phase is the highest in the composition γ=0.30. It is supposed that the compounds with γ?0.35 represent an antiferromagnetic medium with inclusions of the ferromagnetic phase. The strongly reduced samples exhibit a large magnetoresistance below the temperature, at which the spontaneous magnetization develops. The magnetic phase diagrams of both La_0.70Ca_0.30MnO_3−γ and La_0.50Ca_0.50MnO_3−γ systems have been constructed. We argue, that the oxygen vacancies are disordered in the La_0.70Ca_0.30MnO_3−γ system in the studied region of oxygen vacancies concentration (0?γ<0.20) whereas for the La_0.50Ca_0.50MnO_3−γ they tend to order at γ>0.25 in a manner of Sr₂Fe₂O₅-type crystal structure. This study shows that Mn³⁺-O-Mn³⁺ ferromagnetic interaction may play an important role in the formation of magnetic state of manganites.     

Magnetic properties of quasi-two-dimensional La1−xSr1+xMnO4 and the evolution of itinerant electron ferromagnetism in the SrO · (La1−xSrxMnO3)n system

Quasi-two-dimensional oxides of the La_1−xSr_1+xMnO₄ system, possessing the K₂NiF₄ structure, show no evidence for ferromagnetic ordering in contrast to the corresponding three-dimensional La_1−xSr_xMnO₃ perovskites. Instead, there is an increasing tendency toward antiferromagnetic ordering with increasingx in La_1−xSr_1+xMnO₄. Furthermore, these oxides are relatively high-resistivity materials over the entire compositional range. Substitution of Ba for Sr in La_0.5Sr_1.5MnO₄ decreases the ferromagnetic interaction. Increasing the number of perovskite layers in SrO · (La_1−xSr_xMnO₃)_n causes an increase in electrical conductivity as well as ferromagnetic interaction. The oxide becomes a highly conducting ferromagnet whenn ≥ 2.     

Effect of strontium deficiency on the critical behavior at paramagnetic to ferromagnetic phase transition in La0.57Nd0.1Sr0.33MnO3 manganite oxide

The samples of manganese perovskite La_0.57Nd_0.1Sr_0.33−x_xMnO₃ (0.00 ≤ x ≤ 0.05) ( is the strontium deficiency) are prepared by solid-state methods, and all of them have a rhombohedral perovskite structure, revealed by X-ray diffraction. The critical properties of the samples around the paramagnetic–ferromagnetic phase transition were investigated through various techniques such as modified Arrott plot (MAP), Kouvel–Fisher (KF) method and critical isotherm (CI) analysis based on the data of static magnetic measurements recorded around the Curie temperature T_C. The experimental results have revealed that the samples exhibited the second-order magnetic phase transition and the critical exponents of β and γ for La_0.57Nd_0.1Sr_0.33MnO₃ are close to those found out by the 3D-Heisenberg model. Furthermore, the estimated critical exponents of La_0.57Nd_0.1Sr_0.33−x_xMnO₃ (x = 0.025 and 0.05) are consistent with the prediction of the 3D-Ising model. We deduced, following the Harris criterion, that the disorder in our case is relevant which can be the cause of the change in the universality class and we noted that the critical exponents β are almost similar to the value of the mean-field theory which can be explained by the existence of a long-range dipole–dipole interaction.     

Structure, magnetism and transport of the perovskite manganites Ln0.5Ca0.5MnO3 (Ln=Ho, Er, Tm, Yb and Lu)

It was found that the manganese perovskite oxides Ln_0.5Ca_0.5MnO₃ (Ln=Ho, Er, Tm, Yb and Lu) have an orthorhombic structure (space group Pnma). The Mn-O-Mn angles were calculated to be ∼148-150°, revealing an existence of a large crystallographic distortion in these oxides. Electrical resistivity measurements indicated both an insulating nature and a small magnetoresistance effect, both of which are owing to narrow bandwidths of the Mn-3d electrons arising from the crystallographic distortion. DC magnetization measurements showed the three characteristic temperatures, which could be assigned to charge-order, antiferromagnetism of Mn moments, and possible glassy states. All of these temperatures were decreased for the heavier Ln ions, which is explained in connection with both a difference of ionic radii of Ln³⁺ and Ca²⁺, and a lowering of electron transfer. The charge-ordering transition was not clearly observed only for Lu_0.5Ca_0.5MnO₃ containing the smallest lanthanide ion, plausibly due to a large randomness of magnetic interactions arising from the ionic radii difference of Lu³⁺ and Ca²⁺. In addition, preliminary measurements of AC dielectric response suggested that these manganites belong to a so-called multiferroic system.     

A comparative study of the electron- and hole-doped compositions of single crystalline Nd1−xCaxMnO3 ( and 0.4) by Brillouin scattering

In order to understand the differences between the nature of the electron- and the hole-doped compositions of rare earth manganates, properties of single crystals of Nd_1−xCa_xMnO₃ with x=0.6 and 0.4 have been investigated. In the electrical resistivity measurements, the electron-doped (x=0.6) composition shows no effect of magnetic field unlike the hole-doped (x=0.4) composition, but both exhibit similar current-induced changes. Brillouin scattering studies show that the x=0.6 and 0.4 compositions show softening of the modes on cooling the samples towards charge-ordering transitions. The strength of coupling between the e_g orbitals and the elastic strain is considerably larger in the hole-doped composition containing a larger population of Mn³⁺ ions.     

Effects of magnesium substitution on the magnetic properties of Nd0.7Sr0.3MnO3

Effects of magnesium substitution on the magnetic properties of Nd_0.7Sr_0.3MnO₃ have been investigated by neutron powder diffraction and magnetization measurements on polycrystalline samples of composition Nd_0.7Sr_0.3MnO₃, Nd_0.6Mg_0.1Sr_0.3MnO₃, Nd_0.6Mg_0.1Sr_0.3Mn_0.9Mg_0.1O₃, and Nd_0.6Mg_0.1Sr_0.3Mn_0.8Mg_0.2O₃. The pristine compound Nd_0.7Sr_0.3MnO₃ is ferromagnetic with a transition temperature occurring at about 210 K. Increasing the Mg-substitution causes weakened ferromagnetic interaction and a great reduction in the magnetic moment of Mn. The Rietveld analyses of the neutron powder diffraction (NPD) data at 1.5 K for the samples with Mg concentration, y=0.0 and 0.1, show ferromagnetic Mn moments of 3.44(4) and 3.14(4) μ_B, respectively, which order along the [001] direction. Below 20 K the Mn moments of these samples become canted giving an antiferromagnetic component along the [010] direction of about 0.4 μ_B at 1.5 K. The analyses also show ferromagnetic polarization along [001] of the Nd moments below 50 K, with a magnitude of almost 1 μ_B at 1.5 K for both samples. In the samples with Mg substitution of 0.2 and 0.3 only short range magnetic order occurs and the magnitude of the ferromagnetic Mn moments is about 1.6 μ_B at 1.5 K for both samples. Furthermore, the low-temperature NPD patterns show an additional very broad and diffuse feature resulting from short range antiferromagnetic ordering of the Nd moments.     

Structure, Stoichiometry, and Phase Purity of Calcium Substituted Lanthanum Manganite Powders

Calcium-doped lanthanum manganite La_1−xCa_xMnO₃, synthesized by the glycine/nitrate method, was characterized by high resolution synchrotron X-ray powder diffraction, electron diffraction, and infrared spectroscopy. A strong correlation was observed between the cooling rate from the calcination temperature and the powder quality, indicating the importance of a homogeneous oxygen stoichiometry. The structure refinement reveals that La_1−xCa_xMnO₃withx=0.2, 0.3, 0.4, and 0.6 has orthorhombic symmetry with space groupPnma. The MnO₆octahedra are fairly symmetrical, but the octahedra are tilted about 20° relative to the ideal perovskite structure. Infrared spectroscopy revealed that only the O–Mn–O bending mode is significantly influenced by the substitution of La with Ca. In La_0.8Ca_0.2MnO₃we found diffraction evidence of a superstructure in domains in some of the grains. We propose that the superstructure in La_0.8Ca_0.2MnO₃is due to ordering of Ca²⁺ions onA(La³⁺) sites in the perovskiteABO₃structure.     

Spin-glass behavior in Pr0.7Ca0.3CoO3 and Nd0.7Ca0.3CoO3

With a view to investigate the effect of small size of A-site cations on the magnetic properties of the rare earth cobaltates, Ln_1−xA_xCoO₃ (Ln=rare earth, A=alkaline earth), we have investigated Pr_0.7Ca_0.3CoO₃ and Nd_0.7Ca_0.3CoO₃ in detail. For this purpose, we have carried out low-field DC magnetization and ac susceptibility measurements including a study of magnetic relaxation and memory effects. Both Pr_0.7Ca_0.3CoO₃ and Nd_0.7Ca_0.3CoO₃ show frequency-dependent transitions at 70 and 55 K respectively in the ac susceptibility data, due to the onset of spin-glass like behavior. Their relaxation behavior exhibits aging effects. In addition, memory effects are found in the magnetization behavior. These characteristics establish spin-glass behavior in both these cobaltates, a behavior that is distinctly different from that of La_0.7Ca_0.3CoO₃ and La_0.5Sr_0.5CoO₃ which show well-defined ferromagnetic transitions, albeit without long-range ordering.     

Microstructure,magnetoelectric properties and leakage mechanisms of La0.7Ca0.3MnO3/Bi3.15Nd0.85TiO3 composite thin films

A series of high quality Bi_3.15Nd_0.85TiO₃ (BNT) ferroelectric thin films and La_0.7Ca_0.3MnO₃/Bi_3.15Nd_0.85TiO₃ (LCMO/BNT) multiferroic composite thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by chemical solution deposition (CSD) method. The microstructure, surface morphology and leakage mechanisms of BNT and LCMO/BNT composite films were revealed by X-ray diffraction, scanning electron microscopy and semiconductor device analyzer, respectively. Ferroelectric behavior along with a remnant polarization (2P_r) of 20 μC/cm², saturated magnetization around 56 emu/cm³ and magnetoelectric effect (ME) voltage coefficient α_ME of 33 mV/cm Oe at 1 kHz for LCMO/BNT composite films were obtained at room temperature, indicating that the coupling effects of electric and magnetic field exist in the fabricated LCMO/BNT multiferroic composite thin films. And our observations provide an effective way to manipulate the conduction behavior and push forward understanding the leakage mechanism in LCMO/BNT composite films.     

Perovskite-like La1−xKxMnO3 and related compounds: Solid state chemistry and the catalysis of the reduction of NO by CO and H2

The new compounds La_1?xM_xMnO₃ (0.05 ? x ? 0.4 for M = K; x = 0.2 for M = Na, Rb) have been prepared. La_1?xK_xMnO₃ (0.05 ? x ? 0.4), LaMnO_3.01, LaMnO_3.15, La_0.8Na_0.2MnO₃, and La_0.8Rb_0.2MnO₃ have been used as catalysts in the reduction of NO. La_0.8K_0.2MnO₃ has also been used in the catalytic decomposition of NO. The activity of these catalysts is related to the presence of a Mn³⁺/Mn⁴⁺ mixed valence and to the relative ease of forming oxygen vacancies in the solid. The presence of cation vacancies in LaMnO_3.15 and the substitution of La³⁺ by alkali ions in LaMnO₃ increases the catalytic activity. The reduction of NO involves both molecular and dissociative adsorption of NO.     

Al-doped La<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>MnO<Subscript>3</Subscript> as oxide anode for solid oxide fuel cells using dry C<Subscript>3</Subscript>H<Subscript>8</Subscript> fuel

Direct hydrocarbon type solid oxide fuel cells are attractive from simple gas feed process and also high energy conversion efficiency. In this study, La_0.5Sr_0.5MnO₃ (LSM55) perovskite oxide was studied as oxide anode for direct hydrocarbon type solid oxide fuel cell (SOFC). Although reasonable power density like 1 W/cm² and open circuit voltage (OCV) (1.1 V) at 1273 K was exhibited when H₂ was used as fuel, the power density as well as OCV of the cell using LSM55 for anode was significantly decreased when dry C₃H₈ was used for fuel. After power generation measurement, LSM55 phase was decomposed to MnO and La₂MnO₄. Effects of various dopants to Mn site in LSM55 were studied and it was found that partial substitution of Mn in LSM55 with other cation, especially transition metal, is effective for increasing maximum power density. In particular, reasonable high power density can be achieved on the cell using Ni-doped LSM55 for anode. On the other hand, Al substitution is effective for increasing stability against reduction and so, dopant effects of Al were studied in more details for dry C₃H₈ fuel. The power density as well as OCV increased with increasing Al content and the highest power density was achieved at x = 0.4 in La_0.5Sr_0.5Mn_1 ? x Al _x O₃. Among the examined composition, it was found that the cell using La_0.5Sr_0.5Mn_0.6Al_0.4O₃ anode shows the largest power density (0.2 W/cm²) at 1173 K and high OCV (1.01 V) against dry C₃H₈ fuel.     

Synthesis of nanostructured perovskite powders via simple carbonate co-precipitation

A very simple, cost-effective, chloride- and alkali-free, carbonate co-precipitation synthesis in aqueous medium was applied in the preparation of perovskite-type lanthanum manganese oxide-based powders, i.e. La_0.70Sr_0.30MnO_3?δ (LSM) and La_0.75Sr_0.25Cr_0.5Mn_0.5O_3?δ (LSCrM). The precursors so obtained yielded nano-structured perovskite oxides when treated at 900°C and 800°C, respectively. The measured BET surface areas were in the low-end range for high temperature oxides (4 m² g^?1 and 10 m² g^?1) but the X-ray crystallite size was as low as 50 nm for LSCrM and 90 nm for LSM.     

The structure and ordering of zirconium and hafnium containing garnets studied by electron channelling, neutron diffraction and Mössbauer spectroscopy

Garnets, A₃B₂C₃O₁₂, are an important group of minerals and have potential uses in the safe immobilisation of high-level nuclear waste. They have been found naturally to incorporate Zr, Ti and Fe, three elements of interest in the safe storage of nuclear waste. Kimzeyite, Ca₃(Zr,Ti)₂(Si,Al,Fe)₃O₁₂, is a naturally occurring garnet that contains Zr in a high percentage∼30 wt%. For such a material to be of potential immobilisation for nuclear waste the structure needs to be completely understood. Electron channelling studies have shown that the Zr/Ti cations are located on the Y-site, with the Al/Fe cations located on the Z-site. This work has investigated synthetic analogues of kimzeyite, Ca₃(Zr,Hf)₂(Al,Fe,Si)₃O₁₂, by neutron powder diffraction, using the C2 spectrometer at the Chalk River nuclear facility, coupled with ⁵⁷Fe Mössbauer spectroscopy. Such work has allowed the structure of the synthetic material to be determined along with the distribution of cations across the X (CN=8), Y (CN=6), and Z (CN=4) sites. Results have shown that it is possible to synthesise Ca₃(Zr,Hf)₂(Al,Fe,Si)₃O₁₂ with a range of Al/Fe ratios containing Zr and Hf. The Mössbauer data has indicated the Fe is located on the Z site. The structural analyses show that the unit cell changes linearly as a function of composition, and analysis of the disorder indicates that the Zr, Hf reside on the Y site and the Al, Fe, and Si reside on the Z site.     

Enhanced ferromagnetic transition and magnetoresistance in granular Ag-added La0.7Ca0.3MnO3

Granular Ag-added La_0.7Ca_0.3MnO₃ (LCMO) samples were prepared by a sol-gel chemical route. Significant enhancements in Curie temperature (T_C), metal−insulator transition (T_p) and magnetoresistance (MR) effects near room temperature are observed in as-obtained samples. 10 wt% addition of Ag in LCMO causes T_C shift from 272 to 290 K, T_p boost up for more than 100 K and resistivity decrease by more than 3 orders of magnitude. X-ray diffraction patterns, thermal analysis and energy dispersive analysis of X-rays evidently show the existence of metal silver in LCMO matrices. High-resolution electron microscopy illustrates a well crystallization for LCMO grains in existence of Ag. It is argued that improved grain boundary effect and better crystallization caused by Ag addition are responsible for the enhancements.     

Ferromagnetic to spin glass cross over in (La,Tb)2/3Ca1/3MnO3

In the series La_2/3?xTb_xCa_1/3MnO₃, it is known that the compositions are ferromagnetic for smaller values of x and show spin glass characteristics at larger values of x. Our studies on the magnetic properties of various compositions in the La_2/3?xTb_xCa_1/3MnO₃ series show that the cross over from ferromagnetic to spin glass region takes place above x ≈ 1/8. Also, a low temperature anomaly at 30 K, observed in the ac susceptibility curves, disappears for compositions above this critical value of x. A mixed phase region coexists in the narrow compositional range 0.1 ≤ x ≤ 0.125, indicating that the ferromagnetic to spin glass cross over is not abrupt.     

Magnetotransport properties of Mo substituted La0.7Ca0.3Mn1−xMoxO3 perovskites

We studied the effects of Mo substitution on the structural, transport, and magnetic properties of the La_0.7Ca_0.3Mn_1−xMo_xO₃ (x ≤ 0.1) samples. Powder X-ray diffraction analysis reveals that the samples studied crystallize in the orthorhombic structure with space group Pbnm. Both particle size and morphology change significantly as the Mo content x varies. The metal-insulator transition temperature (T_MI) and Curie temperature (T_C) decrease monotonically as x increases. Magnetization data reveal that long-range FM ordering persists in all samples and the saturation moment decreases linearly as x increases. The smaller depression rate of dT_C/dx observed is mainly ascribed to the increased amount of Mn²⁺ ions with Mo doping, which opens the FM coupling between Mn²⁺–O–Mn³⁺ in the samples.     

Critical point of the competition between different orbital- and Bi lone pair-orderings in the Bi-rich part of the BiCaMnO system

The present paper deals with the evidence of an unprecedented ordering in the Bi-rich part of the BiCaMnO diagram, where the spin glass state is observed at low temperature. The χ⁻¹(T) curves of three compounds, corresponding to different Ca/Bi + Ca ratio varying between 0.37 and 0.25, have been characterized and discussed in correlation with the structural transitions as a function of T. Three different behaviours have been observed for Bi_0.63Ca_0.37MnO₃, Bi_0.67Ca_0.33MnO₃ and Bi_0.71Ca_0.24MnO_3−δ. The anomalies in the χ⁻¹(T) curves of Bi_0.71Ca_0.24MnO_3−δ and Bi_0.63Ca_0.37MnO₃ appear to be associated to two different mechanisms, which are not observed in the intermediate Bi_0.67Ca_0.33MnO₃. For the Bi-rich compound, an unprecedented [111]_p-type ordering of the perovskite cell is reported, which is associated to a change of the slope in the magnetic curve. Bi_0.71Ca_0.24MnO_3−δ appears at the convergence point of a complex competition between the complementary lone pair ordering/orbital ordering of the ferromagnetic BiMnO₃ and the charge ordering/orbital ordering of the pseudo CE antiferro-magnetic Bi_0.63Ca_0.37MnO₃.