The substitution of cobalt and nickel for manganese in the perovskite manganate LaBiMn2O6+d; has been realized, leading to the perovskites LaBiMn2-x(M)xO6+d, with M = Co, Ni and x =0-2/3. In contrast to the literature those phases are found to be orthorhombic with Pnma symmetry. More importantly, it is shown that ferromagnetism is enhanced, TC being increased from 80 K for the parent compound (x = 0) to 97 K for Ni-phase, and to 130 K for the Co-phase. Moreover, a strong competition between ferromagnetism and a glassy-ferromagnetic state in the case of nickel or a spin-glass behaviour in the case of cobalt is observed. These phenomena are interpreted in the frame of a phase separation scenario, where the ferromagnetic Mn4+/Ni2+ and Mn4+/Co2+ interactions reinforce the Mn3+/Mn4+ interactions. These compounds are found to be insulating with a relatively large positive value of thermoelectric power.
The defect tolerance nature of organic-inorganic hybrid perovskite is reflected from its stupendous growth in photovoltaic performances. The presence of lattice defect can manipulate or even gives rise to some exceptional properties which otherwise would have remained unseen. One of such properties reported in this article is the experimental observation of defect mediated room temperature ferromagnetism in methylammonium lead halide perovskite for the very first time, ably supported by ab-initio calculations. Theoretical analysis predicts the ferromagnetism principally arises from the iodide …
Single crystals of a new twinned hexagonal perovskite compound Sr8Os6.3O24 have been synthesized, and structural and magnetic properties have been determined. The compound crystallizes in a hexagonal cell with lattice parameters a = 9.6988(3) Å and c = 18.1657(5) Å. The structure is an eight-layered hexagonal B-site deficient perovskite with the layer sequence (ccch)2 and represents the first example of a hexagonal structure among 5d oxides adopting a twin option. The sample shows spontaneous ferromagnetic magnetization below 430 K with a small saturation moment of 0.11 μB/Os ion. This is the …
We have investigated the effect of partial isovalent anion substitution in Ga1-xMnxAs on electrical transport and ferromagnetism. Substitution of only 2.4% of As by P induces a metal-insulator transition at a constant Mn doping of x=0.046 while the replacement of 0.4 % As with N results in the crossover from metal to insulator for x=0.037. This remarkable behavior is consistent with a scenario in which holes located within an impurity band are scattered by alloy disorder in the anion sublattice. The shorter mean free path of holes, which mediate ferromagnetism, reduces the Curie temperature TC…
We use density functional theory calculations to show that the LaAlO3|SrTiO3 interface between insulating perovskite oxides is borderline in satisfying the Stoner criterion for itinerant ferromagnetism and explore other oxide combinations with a view to satisfying it more amply. The larger lattice parameter of an LaScO3|BaTiO3 interface is found to be less favorable than the greater interface distortion of LaAlO3|CaTiO3. Compared to LaAlO3|SrTiO3, the latter is predicted to exhibit robust magnetism with a larger saturation moment and a higher Curie temperature. Our results provide support for …
Ferromagnetism and its evolution in the orthorhombic perovskite system Sr1-xCaxRuO3 have been widely believed to correlate with the structural distortion. The recent development of high-pressure synthesis of the Ba substituted Sr1-yBayRuO3 makes it possible to study ferromagnetism over a broader phase diagram, which includes new orthorhombic Imma and the cubic phases. However, the chemical substitutions introduce the A-site disorder effect on Tc, which complicates determination of the relationship between ferromagnetism and the structural distortion. By clarifying the site disorder effect on T…
Organic or inorganic (A) metal (M) halide (X) perovskites (AMX3) are semiconductor materials setting the basis for the development of highly efficient, low-cost and multijunction solar energy conversion devices. The best efficiencies nowadays are obtained with mixed compositions containing methylammonium, formamidinium, Cs and Rb as well as iodine, bromine and chlorine as anions. The understanding of fundamental properties such as crystal structure and its effect on the band gap, as well as their phase stability is essential. In this systematic study X-ray diffraction and photoluminescense spe…
Solar thermochemical hydrogen production (STCH) is a renewable alternative to hydrogen produced using fossil fuels. While serial bulk experimental methods can accurately measure STCH performance, screening chemically complex materials systems for new promising candidates is more challenging. Here we identify double-site Ce-substituted (Ba,Sr)MnO3 oxide perovskites as promising STCH candidates using a combination of bulk synthesis and high-throughput thin film experiments. The Ce substitution on the B-site in 10H-BaMnO3 and on the A-site in 4P-SrMnO3 lead to 2-3x higher hydrogen production comp…
Extensive studies have been performed on layered compounds, ranging from layered cuprates to van der Waals materials with critical issues of intergrowths and stacking faults. However, such structures have been studied less because of experimental difficulty. We present characteristic defect structures of intergrowths in the Ruddlesden-Popper Ca$_{2.46}$Sr$_{0.54}$Ti$_2$O$_7$, which is known to exhibit hybrid improper ferroelectricity. Transmission electron microscopy reveals that numerous intergrowths composed of 7 and 15 layers are introduced in the ferroelectric domains. Elemental maps demon…
We present results of local spin density approximation (LSDA) pseudopotential calculations for the perovskite structure oxide, bismuth manganite (BiMnO3). The origin of the differences between bismuth manganite and other perovskite manganites is determined by first calculating total energies and band structures of the high symmetry cubic phase, then sequentially lowering the magnetic and structural symmetry. Our results indicate that covalent bonding between bismuth cations and oxygen anions stabilizes different magnetic and structural phases compared with the rare earth manganites. This is co…
Magnetic insulators have been intensively studied for over 100 years, and they, in particular ferrites, are considered to be the cradle of magnetic exchange interactions in solids. Their wide range of applications include microwave devices and permanent magnets . They are also suitable for spintronic devices owing to their high resistivity, low magnetic damping, and spin-dependent tunneling probabilities. The Curie temperature is the crucial factor determining the temperature range in which any ferri/ferromagnetic system remains stable. However, the record Curie temperature has stood for over …
Single phase, sol-gel prepared Cu1-xFexO (0<x<0.125) are characterized in terms of structural, electronic and magnetic properties. Using dielectric and magnetic studies we investigate the coupling of electron and spin. The electrical conductivities and activation energies are studied with increasing Fe content. Modeling of experimental conductivity data emphasizes on a single hopping mechanism for all samples except x=0.125, which have two activation energies. Hole doping is confirmed from Hall effect [1] and by confirming a majority Fe3+ substitution of Cu2+ in CuO from XPS studies. Such a su…
Lead-based halide perovskites are emerging as the most promising class of materials for next generation optoelectronics. However, despite the enormous success of lead-halide perovskite solar cells, the issues of stability and toxicity are yet to be resolved. Here we report on the computational design and the experimental synthesis of a new family of Pb-free inorganic halide double-perovskites based on bismuth or antimony and noble metals. Using first-principles calculations we show that this hitherto unknown family of perovskites exhibits very promising optoelectronic properties, such as tunab…
The magnetic and magnetotransport properties of the oxygen deficient perovskites, SrCo1-xMxO3-d with M = Nb and Ru, were investigated. Both Nb- and Ru-substituted cobaltites are weak ferromagnets, with transition temperatures Tm of 130-150 K and 130-180 K, respectively, and both exhibit a spin glass behavior at temperatures below Tf = 80-90 K. It is demonstrated that there exists a strong competition between ferromagnetism and spin glass state, where Co4+ induces ferromagnetism, whereas Nb or Ru substitution at the cobalt sites induces magnetic disorder, and this particular magnetic behavior i…
PbTiO3 has the highest tetragonal distortion (c/a=1.064) and highest spontaneous polarization among perovskite titanates. But, it is hazardous and hence one needs to reduce Pb content by substituting or reducing Pb content for use in applications. Pb(1-x)(K0.5Sm0.5)xTiO3 (0&x&0.5) perovskite powders were synthesized by sol-gel process, where Pb2+ was replaced by a combination of K+10.5Sm+30.5 (equivalent charge and comparable ionic radius) providing an excellent substitution model to study changes in structural and electrical properties. Vibrational properties and dielectric properties are mod…
Whereas their photophysics exhibits an intricate interplay of carriers with the lattice, most reports have so far relied on single compound studies. With the exception of variations of the organic spacer cations, the effect of constituent substitution on the photophysics and the nature of emitting species, in particular, has remained largely under-explored. Here PEA$_2$PbBr$_4$, PEA$_2$PbI$_4$, and PEA$_2$SnI$_4$ are studied through a variety of optical spectroscopy techniques to reveal a complex set of excitonic transitions at low temperature. We attribute the emergence of weak high energy fe…
We use computational and experimental methods to study d0 ferromagnetism at a charge- imbalanced interface between two perovskites. In SrTiO3/KTaO3 superlattice calculations, the charge imbalance introduces holes in the SrTiO3 layer, inducing a d0 ferromagnetic half-metallic 2D electron gas at the interface oxygen 2p orbitals. The charge imbalance overrides doping by vacancies at realistic concentrations. Varying the constituent materials shows ferromagnetism to be a gen- eral property of hole-type d0 perovskite interfaces. Atomically sharp epitaxial d0 SrTiO3/KTaO3, SrTiO3 /KNbO3 and SrTiO3 /…
Using first principles calculations as based on density functional theory, we propose a class of so far unexplored diluted ferromagnetic semiconductors and half-metals. Here, we study the electronic properties of recently synthesized $ 4d $ and $ 5d $ transition metal dinitrides. In particular, we address Mn- and Fe-substitution in PtN$_2$ and PdN$_2$. Structural relaxation shows that the resulting ordered compounds, Pt$_{0.75}$(Mn,Fe)$_{0.25}$N$_2$ and Pd$_{0.75}$(Mn,Fe)$_{0.25}$N$_2$, maintain the cubic crystal symmetry of the parent compounds. On substitution, all compounds exhibit long-ran…
Based on genetic evolution algorithm, universal structure predictor USPEX assists to explore the most stable structure from Na+ substituting Ca2+ under variable concentration, for p type transparent conductive oxide application. The study finds 2 atoms of NaCa maintain the octahedral packing and cubic phase without the presence of oxygen vacancy, but the electron loss causes in fermi level entering into valence band, realizing p type TCOs character. While others still remain insulator character due to the compensation of oxygen vacancy. Applying Al3+ substituting Ca2+ achieve the fermi level i…
We performed in-situ angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES (SARPES) experiments to investigate the relationship between electronic band structures and ferromagnetism in SrRuO$_3$ (SRO) thin films. Our high-quality ARPES and SARPES results show clear spin-lifted band structures. The spin polarization is strongly dependent on momentum around the Fermi level, whereas it becomes less dependent at high-binding energies. This experimental observation matches our dynamical mean-field theory (DMFT) results very well. As temperature increases from low to the Curie te…
We have synthesized Ga1-xMnxAs1-yPy and Ga1-xMnxP1-yNy by the combination of ion implantation and pulsed-laser melting. We find that the incorporation of isovalent impurities with smaller atomic radii leads to a realignment of the magnetic easy axis in Ga1-xMnxP1-yNy/GaP and Ga1-xMnxAs1-yPy/GaAs thin films from in-plane to out-of-plane. This tensile-strain-induced magnetic anisotropy is reminiscent of that observed in Ga1-xMnxAs grown on larger lattice constant (In,Ga)As buffer layers indicating that the role of strain in determining magnetic anisotropy is fundamental to III-Mn-V materials. In…
The hybrid halide perovskites MAPbI$_{3}$, MAPbI$_{2.94}$Cl$_{0.06}$, and MAPbCl$_{3}$ (MA - methylammonium) have been investigated using inelastic and quasielastic neutron scattering (QENS) with the aim of elucidating the impact of chloride substitution on the rotational dynamics of MA. In this context, we discuss the influence of the inelastic neutron scattering caused by low-energy phonons on the QENS resulting from the MA rotational dynamics in MAPbI$_{3-x}$Cl$_{x}$. Through a comparative temperature-dependent QENS investigation with different energy resolutions, which allow a wide Fourier…
The puzzling observation of room temperature ferromagnetism in double perovskites (A$_2$BB$'$O$_6$), despite having the magnetic lattice of B-ions diluted by non-magnetic B$'$-ions, have been examined for Sr$_2$FeReO$_6$. {\it Ab-initio} spin spiral electronic structure calculations along various high symmetry directions in reciprocal space are used to determine the exchange interactions entering an extended Heisenberg model, which is then solved classically using Monte Carlo simulations to determine the ferromagnetic transition temperature T$_c$. We find that one must consider onsite Coulomb …
Sn/Ge substitution in ((C$_\textrm{n}$H$_{2\textrm{n}-1}$NH$_3$)$_2$PbI$_4$; n=3): An emerging 2D layered hybrid perovskites with enhanced optoelectronic properties$^†$
Recent experimental and theoretical work has shown that the double perovskite NaLaMnWO$_6$ exhibits antiferromagnetic ordering owing to the Mn $d$ states, and computational studies further predict it to exhibit a spontaneous electric polarization due to an improper mechanism for ferroelectricity [King \textit{et al., Phys.\ Rev.\ B}, 2009, \textbf{79}, 224428; Fukushima \textit{et al., Phys.\ Chem.\ Chem.\ Phys.}, 2011, \textbf{13}, 12186], which make it a candidate multiferroic material. Using first-principles density functional calculations, we investigate nine isostructural and isovalent $A…
The electronic and magnetic properties of transition-metal doped $β$-Ge3N4 have been studied using first-principles calculations. The results show that the substitutional transition-metal impurities tend to cluster. The V and Cr doped Ge3N4 compounds are ferromagnetic semiconductors, while the compounds with Mn and Fe doping show a half-metallic ferromagnetic character.
Transient Ferromagnetism in Ultrafast Phase Transitions in Perovskites under XUV Irradiation: A Comparative Study of SrTiO3 and KTaO3
Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）；Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague（布拉格捷克理工大学核科学与物理工程学院）；Institute of Plasma Physics, Czech Academy of Sciences（捷克科学院等离子体物理研究所）
We predict a new candidate high-temperature high-pressure structure of FeSiO$_3$ with space-group symmetry Cmmm by applying an evolutionary algorithm within DFT+U that we call post-perovskite II (PPv-II). An exhaustive search found no other competitive candidate structures with ABO$_3$ composition. We compared the X-ray diffraction (XRD) pattern of FeSiO$_3$ PPv-II with experimental results of the recently reported "H-phase" of (Fe,Mg)SiO$_3$. The intensities and positions of two main X-ray diffraction peaks of PPv-II FeSiO$_3$ compare well with those of the H-phase. We also calculated the sta…
The effect of doping Mo for Mn on the magnetic and transport properties of the colossal magnetoresistance material, La0.67Ba0.33MnO3, has been studied. Compounds of the series La0.67Ba0.33Mn1-xMoxO3 (x=0.0 to 0.1) have been prepared and found to crystallize in the orthorhombic structure (space group Pbnm). Energy Dispersive X-ray Analysis (EDAX) measurements confirm the stoichiometry of all the samples. Magnetotransport and magnetization measurements reveal that the metal-insulator transition temperature (Tp) decreases from 330K for x=0 to 255K for x=0.1. The change in Tp on Mo substitution is…
First-principles density functional theory (DFT) is used to investigate the electronic and magnetic properties of Sr$_4$Rh$_3$O$_{10}$, a member of the Ruddlesden-Popper series. Based on the DFT calculations taking into account the co-operative effect of Coulomb interaction ($U$) and spin-orbit couplings (SOC), Sr$_4$Rh$_3$O$_{10}$ is found to be a half metallic ferromagnet (HMF) with total angular moment $μ_{\rm {tot}}$=12$μ_B$ per unit cell. The material has almost 100$\%$ spin-polarization at the Fermi level despite of sizable SOC. Replacement of Rh atom by the isovalent Co atom is consider…
Single monolayer ferromagnetic perovskite SrRuO3 with high conductivity and strong ferromagnetism
NTT Basic Research Laboratories, NTT Corporation（NTT基础实验室，NTT公司）；The University of Tokyo（东京大学）；Hiroshima University（广岛大学）；Japan Synchrotron Radiation Research Institute (JASRI)（日本同步辐射研究所）
Using density functional theory, we investigate systematically mixed MA(Pb:Sn)X3 perovskites, where MA is CH3NH3+, and X is Cl, Br, or I. Ab initio calculations of the orthorhombic, tetragonal, and cubic perovskite phases show that the substitution of lead by tin has a much weaker influence on both structure and cohesive energies than the substitution of the halogen. The thermodynamic stability of the MA(Pb:Sn)X3 mixtures at finite, non-zero temperatures is studied within the Regular Solution Model. We predict that it will be possible to create MA(Pb:Sn)I3 mixtures at any temperature. Our resu…
Ternary cubic perovskite compounds of the form A_(1/3)A'_(1/3)A''_(1/3)BO_3 and AB_(1/3)B'_(1/3)B''_(1/3)O_3, in which the differentiated cations form an alternating series of monolayers, are studied using first-principles methods. Such compounds are representative of a possible new class of materials in which ferroelectricity is perturbed by compositional breaking of inversion symmetry. For isovalent substitution on either sublattice, the ferroelectric double-well potential is found to persist, but becomes sufficiently asymmetric that minority domains may no longer survive. The strength of th…
We address the role of Sn-substitution and Pb-vacancy (Pb-$\Box$) in regulating stability and carrier concentration of CH$_3$NH$_3$Pb$_{1-X-Y}$Sn$_X$$\Box_Y$I$_3$ perovskite using density functional theory, where the performance of the exchange-correlation functional is carefully analyzed, and validated w.r.t. available experimental results. We find the most stable configuration does not prefer any Pb at 50\% concentration of Sn. However, the Pb-$\Box$s become unfavourable above 250K due to the reduced linearity of Sn-I bonds. For n-type host the Sn substitution is more preferable than Pb-$\Bo…
In order to tune the magnetic properties of the cleavable high-Curie temperature ferromagnet Fe$_{5-x}$GeTe$_2$, the effect of increasing the electron count through arsenic substitution has been investigated. Small additions of arsenic (2.5 and 5%) seemingly enhance ferromagnetic order in polycrystalline samples by quenching fluctuations on one of the three magnetic sublattices, whereas larger As concentrations decrease the ferromagnetic Curie temperature ($T_{\rm C}$) and saturation magnetization. This work also describes the growth and characterization of Fe$_{4.8}$AsTe$_2$ single crystals t…
The samples LaCoO3 with dilute substitutions on cobalt sites have been studied using the resistivity, thermopower and magnetic susceptibility measurements over the temperature range up to ~900 K. The Co-site substitution does not affect the magnetic transition at ~100 K and the onset of massive population of hole carriers at ~500 K, characteristic for undoped LaCoO3. On the other hand, the low-temperature transport and magnetism is markedly distinct for samples with extra charge on cobalt ions introduced by the heterovalent dopants (Mg2+, Ti4+) compared to samples with minor non-stoichiometry …
Halide substitution effects on the photovoltaic properties of Ca$_3$PX$_3$ (X = F, Cl, Br, I) perovskites: advancing solar cell efficiency
Shri Varshney College, Raja Mahendra Pratap Singh University（拉贾·马亨德拉·普拉塔普·辛格大学什里瓦尔什尼学院）；Shri Mata Vaishno Devi University（什里玛塔·瓦伊什诺·德维大学）；Poornima University（普尔尼玛大学）；Graphic Era Deemed to be University（格拉菲克时代大学）；Chandigarh University（昌迪加尔大学）
Ferromagnetic ordering is reported in the post-annealed samples of Co doped n-GaN formed by Co+ implantation. A maximum Curie temperature ~ 250K is recorded for the sample with 8 atomic percent Co. Particle induced x-ray emission-channeling study confirmed the substitutional Co in Ga lattice site. Local atomic arrangement around magnetic impurities is also analyzed using Raman study. A disordered model with carrier mediated coupling of localized magnetic moments is made responsible for the observed ferromagnetic ordering.
The study of the ordered oxygen deficient perovskite EuBaCo2-xNixO5.50 shows that the doping of cobalt sites by nickel induces a strong ferromagnetic component at low temperature in the antiferromagnetic matrix of EuBaCo2O5.50. This system exhibits indeed phase separation, i.e. consists of ferromagnetic domains embedded in the antiferromagnetic matrix of EuBaCo2O5.50. Besides, a magnetic transition is observed for the first time at 40K in the undoped and nickel doped phases, which can be attributed to the ferromagnetic ordering of the Eu3+ moments below this temperature. Moreover sharp ultra m…
We systematically studied the magnetic and transport properties for the polycrystalline samples of Fe-doped perovskite cobaltites: Pr$_{1-y}$Ca$_{y}$Co$_{1-x}$Fe$_x$O$_3$ ($y$=0.3, $x$=0-0.15; $y$=0.45, $x$=0-0.3) and Gd$_{0.55}$Sr$_{0.45}$Co$_{1-x}$Fe$_x$O$_{3}$ ($x$=0-0.3). Fe doping leads to an enhancement of the ferromagnetism in the systems of Pr$_{1-y}$Ca$_{y}$Co$_{1-x}$Fe$_x$O$_3$, while the ferromagnetism is suppressed with further increasing Fe content and spin-glass behavior is observed at high doping level of Fe. In contrast, the ferromagnetism is suppressed in the system Gd$_{0.55}…
We combine the results of magnetic and transport measurements with neutron diffraction data to construct the structural and magnetic phase diagram of the entire family of SrMn$_{1-x}$Ru$_{x}$O$_3$ ($0 \leqslant x \leqslant 1$) perovskites. We have found antiferromagnetic ordering of the C type for lightly Ru-substituted materials ($0.06 \leqslant x \leqslant 0.5$) in a similar manner to $R_{y}$Sr$_{1-y}$MnO$_3$ ($R$=La, Pr), due to the generation of Mn$^{3+}$ in both families of manganite perovskites by either $B$-site substitution of Ru$^{5+}$ for Mn$^{4+}$ or $A$-site substitution of $R^{3+}…
Oxysulfide Perovskites: Reduction of the Electronic Band Gap of RbTaO3 by Sulfur Substitution to Enhance Prospective Solar Cell and Thermoelectric Performances
5d iridates have shown vast emergent phenomena due to a strong interplay among its lattice, charge and spin degrees of freedom, because of which the potential in spintronic application of the thin-film form is highly leveraged. Here we have epitaxially stabilized perovskite SrIr$_{0.8}$Sn$_{0.2}$O$_3$ on [001] SrTiO$_3$ substrates through pulsed laser deposition and systematically characterized the structural, electronic and magnetic properties. Physical properties measurements unravel an insulating ground state with a weak ferromagnetism in the compressively strained epitaxial film. The octah…
The ternary-arsenide compound BaCo2As2 was previously proposed to be in proximity to a quantum-critical point where long-range ferromagnetic (FM) order is suppressed by quantum fluctuations. Here we report the effect of Ir substitution for Co on the magnetic and thermal properties of Ba[Co(1-x)Ir(x)]2As2 (0 <= x <= 0.25) single crystals. These compositions all crystallize in an uncollapsed body-centered-tetragonal ThCr2Si2 structure with space group I4/mmm. Magnetic susceptibility measurements reveal clear signatures of FM ordering for x >= 0.11 with a nearly composition-independent Curie temp…
We have synthesized and characterized laser-deposited film samples of perovskite BaCrO_{3}, a missing member of the perovskite-chromate family. The BaCrO_{3} films have a substantially larger lattice constant than other chromates, are insulating, and exhibit weak ferromagnetism likely associated with canted antiferromagnetism. Comparison with the other sister compounds CaCrO_{3} and SrCrO_{3} suggest an anomalous Mott transition where magnetism is independent of whether the compound is metallic or insulating
The discovery of ferromagnetism in Mn doped GaAs [1] has ignited interest in the development of semiconductor technologies based on electron spin and has led to several proof-of-concept spintronic devices [2-4]. A major hurdle for realistic applications of (Ga,Mn)As, or other dilute magnetic semiconductors, remains their below room-temperature ferromagnetic transition temperature. Enhancing ferromagnetism in semiconductors requires understanding the mechanisms for interaction between magnetic dopants, such as Mn, and identifying the circumstances in which ferromagnetic interactions are maximiz…
We report two solid solutions based on magnetic ion doping of the double perovskite oxide Sr2GaSbO6: Sr2Ga1-xCrxSbO6 (0.1 < x < 0.4) and Sr2Ga1-xFexSbO6 (0.1 < x < 0.4). All compositions crystallize in the same space group (I4/m) as their undoped parent phase Sr2GaSbO6, with the trivalent magnetic cations Cr3+ or Fe3+ partially substituting for non-magnetic Ga3+ in one of the B-cation sites. The Cr- and Fe-doped phases display dominant antiferromagnetic coupling among the dopant magnetic moments, and exhibit decreasing band gaps with increasing substitution level.
Since 2000, the intensive effort in materials research to develop a diluted magnetic semiconductor exhibiting high-temperature (HT) ferromagnetism above room temperature was not successful. Here, the possible first bulk diluted HT-ferromagnetic non-metallic materials, based on the perovskite-type oxynitrides LaTa1-xCox(O,N)3-d (x = 0.01, 0.03, 0.05) are realized. The Curie temperature of the synthesized powders exceeds 600 K and the sample magnetizations are large enough to be directly attracted by permanent magnets. Cobalt clusters as a possible source for the observed HT-ferromagnetism can b…
In the Fe-Mo based B-site ordered double-perovskite, A2FeMoO6.0, with iron in the mixed-valence II/III state, the valence value of Fe is not precisely fixed at 2.5 but may be fine-tuned by means of applying chemical pressure at the A-cation site. This is shown through a systematic 57Fe Mossbauer spectroscopy study using a series of A2FeMoO6.0 [A = (Ba,Sr) or (Sr,Ca)] samples with high degree of Fe/Mo order, the same stoichiometric oxygen content and also almost the same grain size. The isomer shift values and other hyperfine parameters obtained from the Mossbauer spectra confirm that Fe remain…
Hitting hard on the binary halides yields in the formation of Cs2[AgIn]Br6. The lead-free double perovskite marks, although not usable itself, a further step forward in finding sustainable and durable perovskite materials for photovoltaic applications. Cs2[AgIn]Br6 is one of the prominent examples of double perovskites materials that have been suggested to circumvent the use of lead compounds in perovskite solar cells. We herein report the successful synthesis of the material using a mechanochemical approach. It crystallizes in an elpasolite-type structure, an ordered perovskite superstructure…
