Negative Magnetization Phenomena in A-Site Columnar-Ordered Quadruple Perovskites CeMnM(MnSb)O with M = Mn and Zn.

A phenomenon of magnetization reversal in response to an applied magnetic field is very common and forms the basis of magnetic memories. In contrast, the phenomenon of magnetization reversal in response to a temperature change is rarer. In this work, we demonstrated a pronounced negative magnetization effect (NME) during field-cooled measurements in small magnetic fields in members of the A-site columnar-ordered quadruple perovskites, CeMnM(MnSb)O with M = Mn and Zn, which were prepared by a high-pressure, high-temperature method at about 6 GPa and about 1600 K.

A Site-Ordered Quadruple Perovskites, RMnNiMnO with R = Bi, Ce, and Ho, with Different Degrees of B Site Ordering.

A site-ordered quadruple perovskites, AA'BO, can have 3 transition metals at A' and B sites, and show complex magnetic interactions and behavior. Additional complexity appears when B site-ordered arrangements are realized in AA'BB'O. In this work, A site-ordered quadruple perovskites, RMnNiMnO with R = Bi, Ce, and Ho, were prepared by a high-pressure, high-temperature method at about 6 GPa and about 1500 K.

Crystal Structure and Physical Properties of AuAl-Type Suboxides in the Ti-Rh-Si-O and Ti-Ir-Si-O Systems.

This study reports the successful synthesis and comprehensive characterization of TiRhSiO and TiIrSiO, the earliest identified members of Ti-based AuAl-type materials. These compounds crystallize in the cubic space group 23 (No. 198), with refined lattice parameters of 6.

B-Site-Ordered and Disordered Structures in A-Site-Ordered Quadruple Perovskites RMnNiMnO with R = Nd, Sm, Gd, and Dy.

ABO perovskite materials with small cations at the A site, especially with ordered cation arrangements, have attracted a lot of interest because they show unusual physical properties and deviations from general perovskite tendencies. In this work, A-site-ordered quadruple perovskites, RMnNiMnO with R = Nd, Sm, Gd, and Dy, were synthesized by a high-pressure, high-temperature method at about 6 GPa. Annealing at about 1500 K produced samples with additional (partial) B-site ordering of Ni and Mn cations, crystallizing in space group -3.

Three Perovskite Phases with Different Cation Orders in SmMnMn(MnSb)O.

Cation order, which can be controlled by synthesis conditions and stoichiometry, plays an important role in properties of perovskite materials. Here we show that aliovalent doping by Sb in SmMnMn(MnSb)O quadruple perovskite solid solutions can control cation orders in both A and B sites. Samples with 0.

Exotic Magnetism in Perovskite KOsO_{3}.

A new perovskite KOsO_{3} has been stabilized under high-pressure and high-temperature conditions. It is cubic at 500 K (Pm-3m) and undergoes subsequent phase transitions to tetragonal at 320 K (P4/mmm) and rhombohedral (R-3m) at 230 K as shown from refining synchrotron x-ray powder diffraction (SXRD) data. The larger orbital overlap integral and the extended wave function of 5d electrons in the perovskite KOsO_{3} allow to explore physics from the regime where Mott and Hund's rule couplings dominate to the state where the multiple interactions are on equal footing.

Understanding Complex Interplay among Different Instabilities in Multiferroic BiMnO Using Fe Probe Mössbauer Spectroscopy.

Here, we report the results of a Mössbauer study on hyperfine electrical and magnetic interactions in quadruple perovskite BiMnO doped with Fe probes. Measurements were performed in the temperature range of 10 K < < 670 K, wherein BiMnFeO undergoes a cascade of structural ( ≈ 590 K, ≈ 442 K, and ≈ 240 K) and magnetic ( ≈ 57 K, ≈ 50 K, and ≈ 24 K) phase transitions. The analysis of the electric field gradient (EFG) parameters, including the dipole contribution from Bi ions, confirmed the presence of the local dipole moments , which are randomly oriented in the paraelectric cubic phase ( > ).

Anisotropic Thermal Expansion and a Second-Order Charge Order Transition in the Ferrimagnetic DyCuZnMnO Perovskite with Triple A-Site Cation Ordering.

DyCuZnMnO perovskite, belonging to the A-site columnar-ordered quadruple perovskite family with the general composition of AA'A″BO, was prepared by a high-pressure, high-temperature method at 6 GPa and 1500 K. Its crystal structure was studied by synchrotron powder X-ray diffraction between 100 and 800 K. The ideal cation distribution (without antisite disorder) was found to be realized within the sensitivity of the synchrotron X-ray diffraction method.

Ferrimagnetic Ordering and Spin-Glass State in Diluted GdFeO-Type Perovskites (LuMn)(MnTi)O with = 0.25, 0.50, and 0.75.

ABO perovskite materials with small cations at the A site, especially those with ordered cation arrangements, have attracted a great deal of interest because they show unusual physical properties and deviations from the general characteristics of perovskites. In this work, perovskite solid solutions (LuMn)(MnTi)O with = 0.25, 0.

Abnormal Eu → Eu Reduction in CaMnEu(PO) Phosphors: Structure and Luminescent Properties.

β-Ca(PO)-type phosphors CaMnEu(PO) have been synthesized by high-temperature solid-phase reactions. The crystal structure of CaMnEu(PO) was characterized by synchrotron X-ray diffraction. The phase transitions, magnetic and photoluminescence (PL) properties were studied.

High-Pressure Synthesis and Magnetic and Electrical Properties of Fe-Doped BiReO and BiOsO.

Under high-pressure and high-temperature conditions, doped BiReO and BiOsO with Fe up to 29 atomic % were synthesized. The crystal structures and chemical compositions of BiOsFeO and BiReFeO were determined by synchrotron powder X-ray diffraction and electron probe microanalysis. Both crystal structures were explained by a KSbO-type model with the space group 3̅.

Dielectric and Spin-Glass Magnetic Properties of the A-Site Columnar-Ordered Quadruple Perovskite SmCuMn(MnTi)O.

Perovskite-type ABO oxides show a number of cation-ordered structures, which have significant effects on their properties. The rock-salt-type order is dominant for B cations, and the layered order for A cations. In this work, we prepared a new perovskite-type oxide, SmCuMn(MnTi)O, with a rare columnar A-site order using a high-pressure, high-temperature method at about 6 GPa and about 1700 K.

Crystal structure of the cubic double-perovskite SrCrNiOsO.

The crystal structure of the cubic double-perovskite SrCrNiOsO, grown at high pressure, was solved using intensity data measured at 113 K. The Os site was modelled with a partial Ni occupancy, and the Cr site was modelled with both Os and Ni partial occupancy. The refined structure shows that this cubic form is stable at 113 K.

Aurivillius Phase BiVO with d Magnetic Cations, Anisotropic and Negative Thermal Expansion, Multiple Structural Transitions, and Low-Dimensional Magnetism.

Aurivillius phases are an important class of inorganic compounds as they often show ferroelectric properties, and some members of this family are used in nonvolatile ferroelectric memories. The majority of Aurivillius phases have nonmagnetic d cations in the perovskite block. BiTiO is the best-known and extensively studied compound within this family.

Unexpected Phonon Behaviour in BiFeCrO, a Material System Different from Its BiFeO and BiCrO Parents.

The dielectric function and the bandgap of BiFeCrO thin films were determined from spectroscopic ellipsometry and compared with that of the parent compounds BiFeO and BiCrO. The bandgap value of BiFeCrO is lower than that of BiFeO and BiCrO, due to an optical transition at ~2.27 eV attributed to a charge transfer excitation between the Cr and Fe ions.

Structural and Magnetic Phase Transitions in BiFeMnO Solid Solution Driven by Temperature.

The crystal structure and magnetic state of the (1 − x)BiFeO3-(x)BiMnO3 solid solution has been analyzed by X-ray diffraction using lab-based and synchrotron radiation facilities, magnetization measurements, differential thermal analysis, and differential scanning calorimetry. Dopant concentration increases lead to the room-temperature structural transitions from the polar-active rhombohedral phase to the antipolar orthorhombic phase, and then to the monoclinic phase accompanied by the formation of two-phase regions consisting of the adjacent structural phases in the concentration ranges 0.25 < x1 < 0.

KEuTb(MoO) Phosphors for Solid-State Lighting Applications: Aperiodic Structures and the Tb → Eu Energy Transfer.

This paper describes the influence of sintering conditions and Eu/Tb content on the structure and luminescent properties of KEuTb(MoO) (KETMO). KETMO samples were synthesized under two different heating and cooling conditions. A KTb(MoO) (KTMO) colorless transparent single crystal was grown by the Czochralski technique.

Crystal and Magnetic Structure Transitions in BiMnO Ceramics Driven by Cation Vacancies and Temperature.

The crystal structure of BiMnO ceramics has been studied as a function of nominal oxygen excess and temperature using synchrotron and neutron powder diffraction, magnetometry and differential scanning calorimetry. Increase in oxygen excess leads to the structural transformations from the monoclinic structure () to another monoclinic (), and then to the orthorhombic () structure through the two-phase regions. The sequence of the structural transformations is accompanied by a modification of the orbital ordering followed by its disruption.

KTb(MoO) Green Phosphor with K-Ion Conductivity: Derived from Different Synthesis Routes.

The influence of different synthesis routes on the structure and luminescent properties of KTb(MoO) (KTMO) was studied. KTMO samples were prepared by solid-state, hydrothermal, and Czochralski techniques. These methods lead to the following different crystal structures: a triclinic scheelite-type α-phase is the result for the solid-state method, and an orthorhombic KY(MoO)-type γ-phase is the result for the hydrothermal and Czochralski techniques.