Cubic lead perovskite PbMoO3 with anomalous metallic behavior

A previously unreported Pb-based perovskite PbMoO$_3$ is obtained by high-pressure and high-temperature synthesis. This material crystallizes in the $Pm\bar{3}m$ cubic structure at room temperature, making it distinct from typical Pb-based perovskite oxides with a structural distortion. PbMoO$_3$ exhibits a metallic behavior down to 0.1 K with an unusual $T$-sub linear dependence of the electrical resistivity. Moreover, a large specific heat is observed at low temperatures accompanied by a peak in $C_P/T^3$ around 10 K, in marked contrast to the isostructural metallic system SrMoO$_3$. These transport and thermal properties for PbMoO$_3$, taking into account anomalously large Pb atomic displacements detected through diffraction experiments, are attributed to a low-energy vibrational mode, associated with incoherent off-centering of lone pair Pb$^{2+}$ cations. We discuss the unusual behavior of the electrical resistivity in terms of a polaron-like conduction, mediated by the strong coupling between conduction electrons and optical phonons of the local low-energy vibrational mode.Comment: 5 pages, 5 figure

Fatal child abuse-maltreatment syndrome; a case report

Abstract: Child abuse-maltreatment syndrome can be described as child death due to repeated episodes of physical abuse and neglect. Here we present a case of child physical abuse and neglect causing death due to duodenal perforation. A five year old boy was reported to have stomachache occurring one day before death. He was admitted to a private health clinic where he was discharged after an analgesic injection. Because of increasing complaints he was applied to the same clinic, afterwards sent to an Emergency Department where he died during resuscitation. At autopsy, external examination revealed several traumatic injuries and two bite marks of different age, while internal examination revealed 500 ml of dirty yellowishgreenish free liquid in abdominal cavity and a perforation 0.5 cm in diameter of the duodenum wall. Insufficient parental supervision in spite of continuous traumas strongly indicates negligence or intentional abuse by parents. Additionally, insufficient medical follow up, besides; not disclosing the injuries on child's body adds medical malpractice aspect to this case. Key Words: child abuse-maltreatment syndrome, physical abuse of child, child neglect, domestic violence, death A s a recently recognized entity, Child abuse-maltreatment syndrome involves repeated episodes of intentional trauma and negligence of a child, which can result in chronic consequences or death. This syndrome includes a combination of maltreatment types. Examinations of such cases reveal various types of injuries of different age. In most cases, healed older injuries and findings of negligence are accompanied by a recent fatal injury that is the immediate cause of death Inflicted traumatic brain injury is the leading cause of death due to child abuse, while blunt abdominal trauma takes place as the second commonest cause of death among abused children. Duodenal injuries secondary to blunt trauma are rare but generally life threatening A case of death due to child abuse-maltreatment syndrome with multiple types of maltreatment is presented because of its interesting history and dramatic findings accompanied by medical malpractice. Case presentation The presented case, a five year-old boy, was previously diagnosed with mental retardation, attention deficit and hyperactivity disorder and had rehabilitation because of these issues. He had been followed up in a rehabilitation service until the family terminated the treatment. The subject was separated from his biological mother and had been living with his biological father, step mother and two step-siblings wh

Spin-reorientation transitions in the Cairo pentagonal magnet Bi4 Fe5 O13 F

© 2017 American Physical Society. We show that interlayer spins play a dual role in the Cairo pentagonal magnet Bi4Fe5O13F, on one hand mediating the three-dimensional magnetic order, and on the other driving spin-reorientation transitions both within and between the planes. The corresponding sequence of magnetic orders unraveled by neutron diffraction and Mössbauer spectroscopy features two orthogonal magnetic structures described by opposite local vector chiralities, and an intermediate, partly disordered phase with nearly collinear spins. A similar collinear phase has been predicted theoretically to be stabilized by quantum fluctuations, but Bi4Fe5O13F is very far from the relevant parameter regime. While the observed in-plane reorientation cannot be explained by any standard frustration mechanism, our ab initio band-structure calculations reveal strong single-ion anisotropy of the interlayer Fe3+ spins that turns out to be instrumental in controlling the local vector chirality and the associated interlayer order

Anion redox as a means to ferive layered manganese oxychalcogenides with exotic intergrowth structures

Topochemistry enables step-by-step conversions of solid-state materials often leading to metastable structures that retain initial structural motifs. Recent advances in this field revealed many examples where relatively bulky anionic constituents were actively involved in redox reactions during (de)intercalation processes. Such reactions are often accompanied by anion-anion bond formation, which heralds possibilities to design novel structure types disparate from known precursors, in a controlled manner. Here we present the multistep conversion of layered oxychalcogenides Sr2MnO2Cu1.5Ch2 (Ch = S, Se) into Cu-deintercalated phases where antifluorite type [Cu1.5Ch2]2.5- slabs collapsed into two-dimensional arrays of chalcogen dimers. The collapse of the chalcogenide layers on deintercalation led to various stacking types of Sr2MnO2Ch2 slabs, which formed polychalcogenide structures unattainable by conventional high-temperature syntheses. Anion-redox topochemistry is demonstrated to be of interest not only for electrochemical applications but also as a means to design complex layered architectures

Experimental determination of the magnetic interactions of frustrated Cairo pentagon lattice materials

We present inelastic neutron scattering measurements of the Cairo pentagon lattice magnets Bi$_2$Fe$_4$O$_9$ and Bi$_4$Fe$_5$O$_{13}$F, supported by high field magnetisation measurements of Bi$_2$Fe$_4$O$_9$. Using linear spin wave theory and mean field analyses we determine the spin exchange interactions and single-ion anisotropy in these materials. The Cairo lattice is geometrically frustrated and consists of two inequivalent magnetic sites, both occupied by Fe$^{3+}$ ions and connected by two competing nearest neighbour interactions. We found that one of these interactions, coupling nearest neighbour spins on the three-fold symmetric sites, is extremely strong and antiferromagnetic. These strongly coupled dimers are then weakly coupled to a framework formed from spins occupying the other inequivalent site. In addition we found that the Fe$^{3+}$ $S=5/2$ spins have a non-negligible single-ion anisotropy, which manifests as a spin anisotropy gap in the neutron spectrum and a spin-flop transition in high field magnetisation measurements.Comment: 10 pages, 9 figure