Cd2FeReO6: A High-TC Double Perovskite Oxide with Remarkable Tunneling Magnetoresistance.

In this study, we successfully synthesized the double perovskite oxide Cd2FeReO6 by using a high-temperature and high-pressure method. The crystal structure was confirmed to belong to the P21/n space group, exhibiting approximately 68% ordering of Fe3+ and Re5+ ions at the perovskite B-site with the remaining regions showing antisite disorder. The measured Curie temperature of Cd2FeReO6 was 460 K, slightly lower than expected but still significantly above room temperature. Remarkably, Cd2FeReO6 displayed a remarkable low-field butterfly type tunneling magnetoresistance of -23% (-37% between the lowest and the largest values) at 5 K and 90 kOe, the highest among the A2FeReO6 (A = Ca, Sr, Pb, Ba) family. First-principles calculations provided insight into the origin of this observed magnetoresistance behavior, revealing Cd2FeReO6's half-metallic ferrimagnetic nature. This research extends our understanding of the double perovskite family and emphasizes its potential significance in the domains of spintronics and materials science. The exploration of differing magnetoresistance behaviors between Cd2FeReO6 and Ca2FeReO6, along with the influence of antisite disorder in Cd2FeReO6, opens intriguing avenues for further research.

Multiple loss-of-function mutations of carotenoid cleavage dioxygenase 4 reveal its major role in both carotenoid level and apocarotenoid composition in flue-cured mature tobacco leaves.

Apocarotenoid volatiles contribute to the flavor of many agricultural products. In many flowering plants, carotenoid cleavage dioxygenase 4 (CCD4) is involved in the decomposition of carotenoids and resultant production of C13-apocarotenoids, such as ß-ionone derived from ß-carotene. To understand the possible role of tobacco CCD4 genes (NtCCD4-S, NtCCD4-T1 and NtCCD4-T2) in these processes, we analyzed loss-of-function phenotypes. RNA interference transgenic plants showed yellow color in mature (senescent) leaves. Mature leaves of chemically induced double-mutant plants showed a stronger yellow color, and those of triple-mutant plants showed a pronounced yellow color. Carotenoid analysis of the leaves from mutants showed that lutein and ß-carotene increased in line with the degree of color change compared to wild type, whereas there was little change in green color in their young leaves. This result indicates that CCD4s are important for the decomposition of carotenoids in the tobacco leaf maturation process. Analysis of apocarotenoids in flue-cured leaves of the multiple-mutant plants showed that many compounds, including megastigmatrienones, were decreased in comparison to wild type, whereas intriguingly ß-ionone and dihydroactinidiolide were increased. Our results suggest that CCD4s play a key role in both carotenoid level and apocarotenoid composition in flue-cured mature tobacco leaves.

The origin and distribution of 'Kokubu'-type splice-site mutations of the MLO genes in tobacco varieties.

The Japanese domestic tobacco (Nicotiana tabacum L.) cultivar 'Kokubu' shows high powdery mildew resistance that is controlled by splice-site mutations of two MILDEW LOCUS O genes, NtMLO1 and NtMLO2. We investigated the existence of the same NtMLO1/2 splice mutations in the genomes of various tobacco varieties cultivated in Japan and other countries. In total, 14 Japanese domestic cultivars, which were mainly distributed in Kagoshima, had splice-site mutations in both NtMLO1 and NtMLO2. In addition, tobacco cultivars containing only the NtMLO1 splice-site mutation were found in various tobacco production areas in Japan, but no cultivars with only the NtMLO2 splice-site mutation were detected. Moreover, the NtMLO1 splice-site mutation was detected in native Asian, Oriental and cigar tobacco varieties. Consequently, we speculate that these powdery mildew-resistant tobacco cultivars were generated relative recently in the Kagoshima area when a spontaneous mutation occurred at the NtMLO2 splice site in a cultivar already containing the NtMLO1 splice-site mutation and that the NtMLO1 splice-site mutation occurred during the early period of tobacco seed dissemination from the Americas to Asia and Japan.

Inhibition of lateral shoot formation by RNA interference and chemically induced mutations to genes expressed in the axillary meristem of Nicotiana tabacum L.

BACKGROUND: Lateral branches vigorously proliferate in tobacco after the topping of the inflorescence portions of stems for the maturation of the leaves to be harvested. Therefore, tobacco varieties with inhibited lateral shoot formation are highly desired by tobacco farmers. RESULTS: Genetic inhibition of lateral shoot formation was attempted in tobacco. Two groups of genes were examined by RNA interference. The first group comprised homologs of the genes mediating lateral shoot formation in other plants, whereas the second group included genes highly expressed in axillary bud primordial stages. Although "primary" lateral shoots that grew after the plants were topped off when flower buds emerged were unaffected, the growth of "secondary" lateral shoots, which were detected on the abaxial side of the primary lateral shoot base, was significantly suppressed in the knock-down lines of NtLs, NtBl1, NtREV, VE7, and VE12. Chemically induced mutations to NtLs, NtBl1, and NtREV similarly inhibited the development of secondary and "tertiary" lateral shoots, but not primary lateral shoots. The mutations to NtLs and NtBl1 were incorporated into an elite variety by backcrossing. The agronomic characteristics of the backcross lines were examined in field trials conducted in commercial tobacco production regions. The lines were generally suitable for tobacco leaf production and may be useful as new tobacco varieties. CONCLUSION: The suppressed expression of NtLs, NtBl1, NtREV, VE7, or VE12 inhibited the development of only the secondary and tertiary lateral shoots in tobacco. The mutant lines may benefit tobacco farmers by minimizing the work required to remove secondary and tertiary lateral shoots that emerge when farmers are harvesting leaves, which is a labor-intensive process.

DNA marker development by the allele-specific detection of powdery mildew resistance loci derived from Japanese domestic tobacco cultivar 'Kokubu'.

Japanese domestic tobacco (Nicotiana tabacum L.) cultivar 'Kokubu' shows high powdery mildew resistance controlled by recessive alleles at two loci, and these alleles have been widely used as a resource for powdery mildew resistance in tobacco breeding. However, the introduction of this trait by conventional breeding takes much work because of the requirement for test crosses with the parental strains and inoculation tests using active fungi to confirm the introduction of two recessive alleles during back-crossing. Recently, we found that powdery mildew resistance in 'Kokubu' is caused by splice site mutations of two MILDEW LOCUS O genes, NtMLO1 and NtMLO2. Here, we report DNA markers that detect mutations of the NtMLO1/2 genes based on the cleaved amplified polymorphic sequence (CAPS) or allele-specific polymerase chain reaction (AS-PCR) methods. These markers can be used as co-dominant markers that detect heterozygotes of the NtMLO genes at the seedling stage in back-crossed progenies, and will contribute to the simplification of breeding.

Novel MAB phases and insights into their exfoliation into 2D MBenes.

Considering the recent breakthroughs in the synthesis of novel two-dimensional (2D) materials from layered bulk structures, ternary layered transition metal borides, known as MAB phases, have come under scrutiny as a means of obtaining novel 2D transition metal borides, the so-called MBenes. Here, based on a set of phonon calculations, we show the dynamic stability of many Al-containing MAB phases, MAlB (M = Ti, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc), M2AlB2 (Sc, Ti, Zr, Hf, V, Cr, Mo, W, Mn, Tc, Fe, Rh, Ni), M3Al2B2 (M = Sc, T, Zr, Hf, Cr, Mn, Tc, Fe, Ru, Ni), M3AlB4 (M = Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe), and M4AlB6 (M = Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo). By comparing the formation energies of these MAB phases with those of their available competing binary M-B and M-Al, and ternary M-Al-B phases, we find that some of the Sc-, Ti-, V-, Cr-, Mo-, W-, Mn-, Tc-, and Fe-based MAB phases could be favorably synthesized under appropriate experimental conditions. In addition, by examining the strengths of various bonds in MAB phases via crystal orbital Hamilton population and spring constant calculations, we find that the B-B and then M-B bonds are stiffer than the M-Al and Al-B bonds. The different strengths between these bonds imply the etching possibility of Al atoms from MAB phases, consequently forming various 2D MB, M2B3, and M3B4 MBenes. Furthermore, we employ the nudged elastic band method to investigate the possibility of the structural phase transformation of the 2D MB MBenes into graphene-like boron sheets sandwiched between transition metals and find that the energy barrier of the transformation is less than 0.4 eV per atom.

Trends in electronic structures and structural properties of MAX phases: a first-principles study on M(2)AlC (M = Sc, Ti, Cr, Zr, Nb, Mo, Hf, or Ta), M(2)AlN, and hypothetical M(2)AlB phases.

MAX phases are a large family of layered ceramics with many potential structural applications. A set of first-principles calculations was performed for M(2)AlC and M(2)AlN (M = Sc, Ti, Cr, Zr, Nb, Mo, Hf, or Ta) MAX phases as well as for hypothetical M(2)AlB to investigate trends in their electronic structures, formation energies, and various mechanical properties. Analysis of the calculated data is used to extend the idea that the elastic properties of MAX phases can be controlled according to the valence electron concentration. The valence electron concentrationcan be tuned through the various combinations of transition metal and nonmetal elements.

Two-dimensional molybdenum carbides: potential thermoelectric materials of the MXene family.

A newly synthesized family of two-dimensional transition metal carbides and nitrides, so-called MXenes, exhibit metallic or semiconducting properties upon appropriate surface functionalization. Owing to their intrinsic ceramic nature, MXenes may be suitable for energy conversion applications at high temperature. Using the Boltzmann theory and first-principles electronic structure calculations, we explore the thermoelectric properties of monolayer and multilayer M2C (M = Sc, Ti, V, Zr, Nb, Mo, Hf, and Ta) and M2N (M = Ti, Zr, and Hf) MXenes functionalized with F, OH, and O groups. From our calculations, it turns out that monolayer and multilayer nanosheets of Mo2C acquire superior power factors to other MXenes upon any type of functionalization. We therefore propose the functionalized Mo2C nanosheets as potential thermoelectric materials of the MXene family. The exceptional thermoelectric properties of the functionalized Mo2C nanosheets are attributed to the peculiar t2g band shapes, which are a combination of flat and dispersive portions. These types of band shapes allow Mo2C to gain a large Seebeck coefficient and simultaneously a good electrical conductivity at low carrier concentrations.

High-temperature ferrimagnetism driven by lattice distortion in double perovskite Ca2FeOsO6.

5d and 3d hybrid solid-state oxide Ca2FeOsO6 crystallizes into an ordered double-perovskite structure with a space group of P21/n with high-pressures and temperatures. Ca2FeOsO6 presents a long-range ferrimagnetic transition at a temperature of ~320 K (T(c)) and is not a band insulator, but is electrically insulating like the recently discovered Sr2CrOsO6 (T(c) ~725 K). The electronic stat of Ca2FeOsO6 is adjacent to a half-metallic state as well as that of Sr2CrOsO6. In addition, the high-T(c) ferrimagnetism was driven by lattice distortion, which was observed for the first time among double-perovskite oxides and represents complex interplays between spins and orbitals. Unlike conventional ferrite and garnet, the interplays likely play a pivotal role of the ferrimagnetism. A new class of 5d-3d hybrid ferrimagnetic insulators with high-T(c) is established to develop practically and scientifically useful spintronic materials.

The effect of the interlayer element on the exfoliation of layered Mo2AC (A = Al, Si, P, Ga, Ge, As or In) MAX phases into two-dimensional Mo2C nanosheets.

The experimental exfoliation of layered, ternary transition-metal carbide and nitride compounds, known as MAX phases, into two-dimensional (2D) nanosheets, is a great development in the synthesis of novel low-dimensional inorganic systems. Among the MAX phases, Mo-containing ones might be considered as the source for obtaining Mo2C nanosheets with potentially unique properties, if they could be exfoliated. Here, by using a set of first-principles calculations, we discuss the effect of the interlayer 'A' element on the exfoliation of Mo2AC (A = Al, Si, P, Ga, Ge, As or In) MAX phases into the 2D Mo2C nanosheets. Based on the calculated exfoliation energies and the elastic constants, we propose that Mo2InC with the lowest exfoliation energy and the highest elastic constant anisotropy between C11 and C33 might be a suitable compound for exfoliation into 2D Mo2C nanosheets.

High-pressure synthesis, crystal structure, and magnetic properties of KSbO3-type 5d oxides K0.84OsO3 and Bi2.93Os3O11.

5d Solid-state oxides K0.84OsO3 (Os5.16+; 5d2.84) and Bi2.93Os3O11 (Os4.40+; 5d3.60) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500-1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO3-type structure with a space group of Im-3 and Pn-3 was determined for K0.84OsO3 and Bi2.93Os3O11, respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi3Re3O11 (Re4.33+; 5d2.66) and Ba2Ir3O9 (Ir4.66+; 5d4.33). The absence of long-range magnetic order seems to be common among 5d KSbO3-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).

High-pressure synthesis of 5d cubic perovskite BaOsO3 at 17 GPa: ferromagnetic evolution over 3d to 5d series.

In continuation of the series of perovskite oxides that includes 3d(4) cubic BaFeO3 and 4d(4) cubic BaRuO3, 5d(4) cubic BaOsO3 was synthesized by a solid-state reaction at a pressure of 17 GPa, and its crystal structure was investigated by synchrotron powder X-ray diffraction measurements. In addition, its magnetic susceptibility, electrical resistivity, and specific heat were measured over temperatures ranging from 2 to 400 K. The results establish a series of d(4) cubic perovskite oxides, which can help in the mapping of the itinerant ferromagnetism that is free from any complication from local lattice distortions for transitions from the 3d orbital to the 5d orbital. Such a perovskite series has never been synthesized at any d configuration to date. Although cubic BaOsO3 did not exhibit long-range ferromagnetic order unlike cubic BaFeO3 and BaRuO3, enhanced feature of paramagnetism was detected with weak temperature dependence. Orthorhombic CaOsO3 and SrOsO3 show similar magnetic behaviors. CaOsO3 is not as conducting as SrOsO3 and BaOsO3, presumably due to impact of tilting of octahedra on the width of the t2g band. These results elucidate the evolution of the magnetism of perovskite oxides not only in the 5d system but also in group 8 of the periodic table.

A ferroelectric-like structural transition in a metal.

Metals cannot exhibit ferroelectricity because static internal electric fields are screened by conduction electrons, but in 1965, Anderson and Blount predicted the possibility of a ferroelectric metal, in which a ferroelectric-like structural transition occurs in the metallic state. Up to now, no clear example of such a material has been identified. Here we report on a centrosymmetric (R3c) to non-centrosymmetric (R3c) transition in metallic LiOsO3 that is structurally equivalent to the ferroelectric transition of LiNbO3 (ref. 3). The transition involves a continuous shift in the mean position of Li(+) ions on cooling below 140 K. Its discovery realizes the scenario described in ref. 2, and establishes a new class of materials whose properties may differ from those of normal metals.

Neutron diffraction study of unusual phase separation in the antiperovskite nitride Mn3ZnN.

The antiperovskite Mn(3)ZnN is studied by neutron diffraction at temperatures between 50 and 295 K. Mn(3)ZnN crystallizes to form a cubic structure at room temperature (C1 phase). Upon cooling, another cubic structure (C2 phase) appears at around 177 K. Interestingly, the C2 phase disappears below 140 K. The maximum mass concentration of the C2 phase is approximately 85% (at 160 K). The coexistence of C1 and C2 phase in the temperature interval of 140-177 K implies that phase separation occurs. Although the C1 and C2 phases share their composition and lattice symmetry, the C2 phase has a slightly larger lattice parameter (Δa ≈ 0.53%) and a different magnetic structure. The C2 phase is further investigated by neutron diffraction under high-pressure conditions (up to 270 MPa). The results show that the unusual appearance and disappearance of the C2 phase is accompanied by magnetic ordering. Mn(3)ZnN is thus a valuable subject for study of the magneto-lattice effect and phase separation behavior because this is rarely observed in nonoxide materials.

High-pressure synthesis, crystal structure, and electromagnetic properties of CdRh2O4: an analogous oxide of the postspinel mineral MgAl2O4.

The postspinel mineral MgAl(2)O(4) exists only under the severe pressure conditions in the subducted oceanic lithosphere in the Earth's deep interior. Here we report that its analogous oxide CdRh(2)O(4) exhibits a structural transition to a quenchable postspinel phase under a high pressure of 6 GPa at 1400 °C, which is within the general pressure range of a conventional single-stage multianvil system. In addition, the complex magnetic contributions to the lattice and metal nonstoichiometry that often complicate investigations of other analogues of MgAl(2)O(4) are absent in CdRh(2)O(4). X-ray crystallography revealed that this postspinel phase has an orthorhombic CaFe(2)O(4) structure, thus making it a practical analogue for investigations into the geophysical role of postspinel MgAl(2)O(4). Replacement of Mg(2+) with Cd(2+) appears to be effective in lowering the pressure required for transition, as was suggested for CdGeO(3). In addition, Rh(3+) could also contribute to this reduction, as many analogous Rh oxides of aluminous and silicic minerals have been quenched from lower-pressure conditions.

Crystal growth and structure and magnetic properties of the 5d oxide Ca3LiOsO6: extended superexchange magnetic interaction in oxide.

Crystals of the newly synthesized compound Ca(3)LiOsO(6) were grown by a flux method using LiCl and KCl, followed by single-crystal X-ray diffraction (XRD), low-temperature powder XRD, and measurements of ac and dc magnetic susceptibility and specific heat. The data indicate that Ca(3)LiOsO(6) has a fully opened electronic gap with an antiferromagnetic ordered state, consistent with suggestions from the first-principles study. The observed magnetic transition temperature is 117 K, too high to be caused only by a direct spin-spin interaction. It appears that the original superexchange magnetic path Os-O-Os is absent; thus, the extended superexchange path (Os-O)-(O-Os) can be expected to be responsible for the 117 K magnetic order. If this is true, Ca(3)LiOsO(6) would be highly valuable to study the nature of extended superexchange magnetic interactions in solids.

Effects of hydrogen in working gas on valence States of oxygen in sputter-deposited indium tin oxide thin films.

X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy-elastic recoil detection analysis (RBS-ERDA) revealed that hydrogen in working gas for dc-plasma sputter deposition resided in indium tin oxide (ITO) films and generated the O(-) state seen as the suboxide-like O 1s peak in XPS. Growth of the suboxide-like O 1s peak was parallel with an increase of the resided hydrogen quantified by RBS-ERDA. The first-principles band structure calculation revealed that the electronic structure of In(2)O(3) crystal was realized typically for the most conductive as-deposited film grown in the gas containing hydrogen of 1%. The as-deposited film grown in the gas containing hydrogen of more than 1% exhibited rather high density but low mobility of carriers and showed the electronic structure above 4 eV originated from the O(-) state due to the resided hydrogen in addition to that of the most conducting one. Both well preserved In(2)O(3) band structure and proper concentration of the O(2-) vacancy are indispensable for achieving the highest conductivity; however, the O(-) state lowers efficiency of the carrier doping using the O(2-) vacancy in the lattice and increases density of the ionized scattering center for the carriers.

Synthesis and magnetic and charge-transport properties of the correlated 4d post-perovskite CaRhO3.

A high-quality polycrystalline sample of the correlated 4d post-perovskite CaRhO(3) (Rh(4+): 4d(5), S(el) = 1/2) was attained under a moderate pressure of 6 GPa. Since the post-perovskite is quenchable at ambient pressure/temperature, it can be a valuable analogue of the post-perovskite MgSiO(3) (stable higher than 120 GPa and unstable at ambient pressure), which is a significant key material in earth science. The sample was subjected for measurements of charge-transport and magnetic properties. The data clearly indicate it goes into an antiferromagnetically ordered state below approximately 90 K in an unusual way, in striking contrast to what was observed for the perovskite phase. The post-perovskite CaRhO(3) offers future opportunities for correlated electrons science as well as earth science.

Magnetoresistance and microstructure of magnetite nanocrystals dispersed in indium-tin oxide thin films.

Epitaxial indium-tin oxide (ITO) thin films were fabricated on a yttria-stabilized zirconia (YSZ) substrate by pulsed-laser deposition using magnetite (Fe(3)O(4)) nanoparticle dispersed ITO powders as a target. Magnetoresistance of the film at a field of 1 T was 39% at 45 K, and it stayed at 3% above 225 K. The film demonstrated cooling hysteresis in the temperature dependence of direct-current magnetization. Transmission electron microscopy revealed that phase-separated Fe(3)O(4) nanocrystals with widths of approximately 40-150 nm and heights of approximately 10-25 nm precipitated and grew epitaxially on the substrate in the film. Both the Fe(3)O(4)(111) and ITO(001) planes were parallel to the YSZ(001) plane. The Fe(3)O(4)(11-2) and -(1-10) planes were parallel to the ITO(100) and -(010) planes, respectively, and the planes connected smoothly at the grain boundary. The contour map of the electron density for the Fe(3)O(4)(111) plane by the first-principles electronic structure computation was similar to that for the ITO(001) plane. The [111]-oriented Fe(3)O(4) nanocrystals played the role of spin aligner for charge carriers of the epitaxial ITO film.

Occult gallbladder carcinoma after laparoscopic cholecystectomy: a report of four cases.

Eighty-four patients underwent laparoscopic cholecystectomy (LC) from January through August 2006. Of these patients, 4 (4.7%) were found to have occult gallbladder carcinoma (GC) either during or after the procedure. Two of the patients were women and 2 were men. The mean age was 75.0 years. One patient had mucosal tumors, 2 had subserosal tumors, and 1 had a serosal lesion. One of the 2 patients with subserosal tumors underwent radical surgery. In a previous study, 0.83% (10 of 1,195) of patients who had undergone LC were found to have occult GC, either during of after the procedure. The prevalence of gallbladder carcinoma has recently been increasing. GC has been reported in 0.3% to 1.5% of patients who have undergone cholecystectomy. Since the introduction of laparoscopic surgery, the number of cholecystectomies being performed has increased, which may explain why occult GC seems to be occurring more frequently. The prognosis for GC is poor, and surgical resection is the only potentially curative treatment. However, GC is difficult to diagnose at an early stage and difficult to recognize even in the advanced stages. Fifteen percent to 30% of patients show no preoperative or intraoperative evidence of malignancy. Occult GC is also increasing. Because flat infiltrating GC and GC with cholecystitis and numerous stones are difficult to diagnose preoperatively, we recommend taking frozen sections from patients who are of advanced age (older than 70 years), have a long history of stones, or have a thickened gallbladder wall.