Multiferroic materials have been the subject of intense study, but it remains a great challenge to synthesize those presenting both magnetic and ferroelectric polarizations at room temperature. In this work, we have successfully obtained LiNbO3-type ScFeO3, a metastable phase converted from the orthorhombic perovskite formed under 15 GPa at elevated temperatures. A combined structure analysis by synchrotron X-ray and neutron powder diffraction and high-angle annular dark-field scanning transmission electron microscopy imaging reveals that this compound adopts the polar R3c symmetry with a fully ordered arrangement of trivalent Sc and Fe ions, forming highly distorted ScO6 and FeO6 octahedra. The calculated spontaneous polarization along the hexagonal c-axis is as large as 100 μC/cm(2). The magnetic studies show that LiNbO3-type ScFeO3 is a weak ferromagnet with TN = 545 K due to a canted G-type antiferromagnetic ordering of Fe(3+) spins, representing the first example of LiNbO3-type oxides with magnetic ordering far above room temperature. A comparison of the present compound and rare-earth orthorhombic perovskites RFeO3 (R = La-Lu and Y), all of which possess the corner-shared FeO6 octahedral network, allows us to find a correlation between TN and the Fe-O-Fe bond angle, indicating that the A-site cation-size-dependent octahedral tilting dominates the magnetic transition through the Fe-O-Fe superexchange interaction. This work provides a general and versatile strategy to create materials in which ferroelectricity and ferromagnetism coexist at high temperatures.

We prepared a new two-dimensional oxyantimonide, BaTi 2 Sb 2 O, which shows a superconducting transition at 1.2 K, representing the first superconductivity in a system with Ti 3þ (d 1 ) in a square lattice. The TiO 2 Sb 4 mixed anionic coordination stabilizes a unique half-filled Ti d xy orbital configuration in Ti 2 O plane, which is analogous to Cu 2þ (d 9 ) in the high-T c superconductors. A charge density wave (CDW)-or spin density wave (SDW)-like anomaly appears at 50 K, which is significantly reduced compared with 200 K for the isostructural and non-superconducting BaTi 2 As 2 O.Since the discovery of high-T c superconductivity in cuprates, 1) there has been a longstanding quest to find novel superconductors. Although several classes of materials such as MgB 2 , iron pnictides, and fullerides show high T c 's, 2-4) the cuprates still hold the highest T c record. Yet, the mechanism for its occurrence is unclear and still under debate despite intense investigation. To clarify the mechanism of high-T c superconductivity, there have been a variety of attempts to find a novel superconductor that is isostructural and isoelectric with the high-T c cuprates. One plausible approach is carrier doping into a perovskite oxide with a 3d 1 electron configuration, such as AE 2 V 4þ O 4 (AE = Sr, Ba). Here, the electronic configuration is complementary with respect to the 3d 9 cuprates; although La 2 Cu 2þ O 4 has one hole per Cu 2þ , AE 2 V 4þ O 4 has one electron per V 4þ . However, as will be discussed later, this view can be seen as an oversimplified description, since it neglects orbital degeneracy derived from the octahedral crystal field around the transition metal. In fact, experimentally, carrier-doped AE 2 V 4þ O 4 does not show superconductivity, but shows metallic conductivity. 5,6) As shown in Fig. 1, the titanium oxypnictides Na 2 Ti 3þ 2 Pn 2 O (Pn = As, Sb) 7) and La 2 CuO 4 are somewhat similar in structure. Na 2 Ti 2 Pn 2 O has a Ti 2 O square net that adopts the anticonfiguration to the CuO 2 square net in La 2 CuO 4 . In this net, Ti 3þ (3d 1 ) is coordinated octahedrally by two oxide anions and four pnictide anions, and these TiO 2 Pn 4 octahedra share edges to form the square lattice. BaTi 2 As 2 O [ Fig. 1(c)], where the two sodium cations have been replaced with one barium cation, has the same square lattice framework and has recently been reported. 8) The mixed anionic coordination of TiO 2 Pn 4 and the octahedral connectivity in the ab plane, as shown in Fig. 1(f ), provide a unique opportunity for the t 2g orbitals to split to a greater extent (relative to pure oxide coordination), owing to the anions having different valences, electronegativities, and ionic radii.Unfortunately, none of these compounds show superconductivity. 9,10) Interestingly, the susceptibility and resistivity showed an anomaly at T a ¼ 330 K for Na 2 Ti 2 As 2 O, 120 K for Na 2 Ti 2 Sb 2 O, and 200 K for BaTi 2 As 2 O, which is ascribed to a CDW or SDW (CDW/SDW) transition. Given that CDW/SDW instabilities are also commonly ...

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The oxyhydride solid solutions (Ca,Sr)TiO(3-x)H(x) and (Sr,Ba)TiO(3-x)H(x) have been prepared by reducing the corresponding ATiO(3) oxides with calcium hydride. Under the reaction conditions examined, a hydride content of x = 0.1-0.3 was obtained for all compositions. Compared to our previous result with BaTiO(3-x)H(x), the larger particle size in this study (20-30 μm vs 170 nm) resulted in a somewhat lower hydride amount despite prolonged reaction times. We examined changes in cell volume, octahedral tilt angle, and site occupancy of different anion sites after conversion to oxyhydrides; it appears that these oxyhydrides fit the geometrical descriptions typical for regular ABO(3) perovskites quite well. The hydrogen release temperature, previously shown to be indicative of the hydride exchange temperature, however, does not scale linearly with the A-site composition, indicating a potential effect of chemical randomness.

The ECHIDNA high‐resolution neutron powder diffractometer at the 20 MW OPAL research reactor in Australia produces high‐quality data for a broad spectrum of crystal and magnetic structural studies. The paper presents an overview of the current status of the hardware, latest developments in data‐reduction software, statistics on instrument usage and the user programme, and instrument limitations.