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Magnetic and dielectric properties have been studied for LaCrO3, PrCrO3, and their solid solution La0.5Pr0.5CrO3, which belong to a family of the ferroelectric orthochromite series RCrO3 (R: rare earths). The magnetic measurements confirm that the materials show canted antiferromagnetic ordering at 240–288 K. Neutron diffraction patterns could be fitted with the centrosymmetric Pnma, which is different from the non-centrosymmetric structure proposed for the ferroelectric phase of NdCrO3. The large dielectric constants are likely due to the hopping of charge carriers as proposed previously for other chromites.

Magnetic and dielectric properties of perovskite manganites R 0.5 Sr 0.5 MnO 3 ( R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at T g ∼ 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R 3+ and Sr 3+ settled randomly at the same crystallographic site. Dielectric constants for each material were ∼1000–10,000 between ∼50 and ∼300 K and showed broad maximums above T g . Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R /Sr site. The tan δ and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3 d electrons.

The polarization analysis options on the thermal neutron triple-axis spectrometer TAS-1 at JRR-3 of Japan Atomic Energy Agency (JAEA) have been improved as a result of an upgrading program of the Advanced Science Research Center. In order to increase the polarized neutron intensity, we have replaced the previous flat polarizing Cu 2 MnAl (Heusler) monochromator and analyzer with doubly focusing ones. Intensity gain factors of more than 30 have been achieved for 14.7 meV neutrons in measurements of incoherent neutron scattering of vanadium. Using the new monochromator and analyzer, elastic and inelastic polarized neutron scattering experiments with the conventional setup for one-dimensional polarization analysis and with CRYOPAD (Cryogenic Polarization Analysis Device) for three-dimensional polarization analysis are now routinely performed on TAS-1.

The magnetic and dielectric properties of a perovskite manganite Tb0.5Ca0.5MnO3 were investigated. Magnetic measurements showed three characteristic temperatures, originating from charge ordering (~300 K), antiferromagnetic ordering (~120 K), and a transition to a glassy state (~50 K). The coexistence of the charge and antiferromagnetic orderings was confirmed by powder neutron diffraction. AC dielectric measurements showed large dielectric constants larger than ~1000 at approximately room temperature. The temperature dependence of the dielectric constant changed just below the charge-ordering temperature. From the analysis of tan δ, the activation energy for switching the directions of polar regions was calculated to be ~0.09 eV, which is close to the activation energy of the Mn 3d electron transfer. These results strongly suggest that the dielectric properties of this material are governed by the ordering and transfer of the Mn 3d charges.

We have investigated crystal structures and magnetic properties of cobalt chalcogenides BaLa2Co(S1 − xSex)5 (0.0 ≤ x ≤ 0.4). This system has a tetragonal crystal structure with the space group I4/mcm. The lattice constants a and c increase linearly with Se content x. The temperature dependence of the magnetic susceptibilities of BaLa2Co(S1 − xSex)5 shows that the antiferromagnetic transition temperature (63–65 K) increases and the magnetic moment of Co2+ decreases with increasing x. Their specific heat shows the decrease of the Debye temperatures with increasing x. The neutron diffraction data collected at 10 K for BaLa2CoS5 indicate that the Co2+ ions have a collinear antiferromagnetic structure with an ordered moment of 3.56 μB. The magnetic moments lie in a parallel direction with the c-axis.

Magnetic properties of a quaternary oxide Ba 3 NdRu 2 O 9 are reported. This compound adopts the 6H-perovskite structure with space group P 6 3 / mmc , in which the cation sites within the face-sharing octahedra are occupied by ruthenium ions and those within the corner-sharing octahedra are occupied by neodymium ions. Powder neutron diffraction, powder X-ray diffraction, magnetic susceptibility, magnetization, and specific heat measurements were carried out. It was found that the crystal phase transition and magnetic transition occurred at ca . 120 K and 24 K, respectively. The crystal structure below 120 K is monoclinic with space group C 2/ c . Neutron diffraction data collected at 10 K show that Ba 3 NdRu 2 O 9 has a long-range ferromagnetic ordering of Nd 3+ ions. The ordered magnetic moment of Nd 3+ ions is 1.65(8) μ B . The direction of ordered moments is parallel to the c -axis.

The ordered perovskite compound Ba2PrRuO6 is prepared and its magnetic properties are investigated. The Rietveld analysis of the neutron diffraction profiles measured at 150 K shows that the Pr3+ and Ru5+ ions are arranged with regularity over the six-coordinate B sites of the perovskite ABO3 and that Ba2PrRuO6 belongs to space group P21/n, with a = 6.0063(5), b = 5.9863(4), c = 8.4677(7) A and 90.04(2)°. The magnetic susceptibility and the heat capacity measurements show that this compound transforms to an antiferromagnetic state below 117 K. From the neutron diffraction patterns measured at 7 K, the magnetic structure is determined to be of Type I and the magnetic moments of Pr3+ and Ru5+ are estimated to be 2.2(1) and 2.0(2) µB, respectively. Their values are discussed on the basis of theoretical calculations for the crystal field splitting.

The magnetic properties of the perovskite-type compounds La1-xSrxCrO3 (x = 0.05 and 0.15) have been investigated. In the magnetic susceptibility measurements, three magnetic anomalies have been observed for La0.95Sr0.05CrO3 (at 21 K, 85 K and 280 K) and for La0.85Sr0.15CrO3 (at 26 K, 160 K and 267 K). Powder neutron diffraction measurements on these two compounds indicate that the anomaly found at ≈20 K in their susceptibility-temperature curves is not ascribable to the magnetic transition. Heat capacity measurements also show that two anomalies have been found at 90 K and 280 K for La0.95Sr0.05CrO3 and at 160 K, 190 K and 266 K for La0.85Sr0.15CrO3, and no anomaly has been found at ≈20 K. The magnetic structures for all the compounds have been determined to be of G type, in which Cr atoms are antiferromagnetically coupled with the six neighbouring Cr atoms at all of the temperatures. The magnetic moments of Cr atoms are directed parallel to the z-axis of an orthorhombic unit cell for La0.95Sr0.05CrO3 at 10 K and 50 K and for La0.85Sr0.15CrO3 at 10 K and 50 K; the Gz mode dominates. The Gy mode dominates for La0.95Sr0.05CrO3 at 125 K; i.e., a spin reorientation has occurred between 50 K and 125 K.

Magnetic properties of an ordered perovskite compound Sr2HoRuO6 have been reported. Powder neutron diffraction measurements at 10 K, 25 K and room temperature were performed to investigate the crystal and magnetic structures of Sr2HoRuO6. As a result of the refinement of the data collected at room temperature, it was found that the crystal structure of this compound is a distorted perovskite [a = 5.7710(3) A, b = 5.7801(3) A, c = 8.1640(4) A and β = 90.200(3)°] with space group P21/n and a 1∶1 ordered arrangement of Ru5+ and Ho3+ over the six-coordinate B sites. Data collected at 10 and 25 K show that Sr2HoRuO6 has a long range antiferromagnetic ordering involving both Ru5+ and Ho3+. The direction of the magnetic moments is along the c-axis. Each of these orders in a type I arrangement and these magnetic moments are antiparallel in the ab-plane with each other. Magnetic susceptibility measurements from 5 to 300 K showed the existence of a magnetic transition at 36 K and divergence between zero-field and field cooled conditions below this temperature. The field-dependence of the magnetization was measured and a small magnetic hysteresis loop was found below the divergence temperature indicating the existence of a weak ferromagnetic moment associated with the antiferromagnetism.

The magnetic properties of the ordered perovskite compound Ba2NdRuO6 are reported. Powder neutron diffraction measurements were performed at 100, 35 and 7 K to determine its crystal structure and magnetic properties. Refinement of the data collected at 100 K showed that this compound has monoclinic symmetry, space group P21/n with a = 5.9888(2), b = 5.9916(2), c = 8.4667(2) A and β = 90.026(3)°, and that the structure is that of a perovskite with a 1∶1 ordered arrangement of Ru5+ and Nd3+ over the 6-coordinate sites. From the data collected at 35 and 7 K, it was found that there is a long range antiferromagnetic ordering in the Ba2NdRuO6. The magnetic structure is of type I and the magnetic moments of Nd3+ and Ru5+ ions are in the same direction in the ab plane.

We have performed powder neutron diffraction measurements for Sr2TbRuO6 at 10 K and room temperature. It has been found that the crystal structure of this compound is a distorted perovskite (a = 5.7932(2) A, b = 5.8107(1) A, c = 8.2011(3) A and β = 90.249(2)°) with the space group P21/n (No.14) and a 1 ∶ 1 ordered arrangement of Ru5+ and Tb3+ over the 6-coordinate B sites. Data collected at 10 K show that Sr2TbRuO6 has long range antiferromagnetic ordering involving both Ru5+ and Tb3+. Each of these ions orders in a type I arrangement. The direction of the magnetic moments is canted by ca. 20° from the c axis. The magnetic susceptibility and specific heat measurements show the existence of magnetic transitions at 32 K and 41 K. The magnetic properties of Sr2TbRu1 − xIrxO6 (0 < x < 1) are also reported in this paper. The structural data and the value of the effective magnetic moment indicate that these compounds adopt the valence configuration of Sr2Tb3+(Ru1 − xIrx)5+O6 (x = 0.0–0.7) or Sr2Tb4+(Ru1 − xIrx)4+O6 (x = 0.85–1.0). Evidence for the presence of a mixed valence state was not found. The magnetic transition temperature for Sr2Tb3+(Ru1 − xIrx)5+O6 decreases with increasing x. On the other hand, that for Sr2Tb4+(Ru1 − xIrx)4+O6 increases with x.

We prepared Ruddlesden–Popper-type layered perovskites Ca2−xSrxMnO4 (x=0–2.0 at 0.25 intervals). Their precise crystal structures at room temperature and at 10 K were determined from both the X-ray and the neutron diffraction measurements. The compounds for x=0 and 0.25 have a tetragonal system with the space group I41/acd (No. 142). The compounds for x=0.5–2.0 have a tetragonal system with the space group I4/mmm (No. 139). Magnetic susceptibility measurements have been performed for all the compounds in the temperature range between 5 and 350 K. The temperature-dependent magnetic susceptibilities were measured under zero-field-cooled (ZFC) and field-cooled (FC) conditions at an applied field of 1000 G. A dramatic difference in magnetic susceptibilities between ZFC and FC was observed below the Neel temperatures for Ca2MnO4 and Ca1.75Sr0.25MnO4, which shows the onset of a ferromagnetic moment below these temperatures. This moment is caused by the Dzyaloshinsky–Moriya interaction. Magnetic structures of Ca2–xSrxMnO4 (x=0.0, 0.5, 1.0, and 1.5) solid solutions at 10 K have been determined by the neutron diffraction measurements. The nearest-neighbor Mn4+ ions are coupled antiferromagnetically in the (001) planes and the spins are parallel to the c axis.

We prepared oxygen stoichiometric and in which tetravalent terbium ions are stabilized at the B sites of the perovskite . Their crystal structures at room temperature and at 10 K were determined from both x-ray and neutron diffraction measurements. Both and have an orthorhombic perovskite-type structure with space group Pnma (No 62). Magnetic susceptibility measurements have been performed for both the compounds in the temperature range between 4.5 K and room temperature. Both the compounds show the antiferromagnetic transition at . The temperature-dependent magnetic susceptibilities were measured with zero-field-cooled (ZFC) and field-cooled (FC) conditions at an applied field of 1000 G. A dramatic difference between ZFC and FC was observed below the Neel temperatures for both the compounds, which shows the onset of a ferromagnetic moment below those temperatures. To determine the magnetic structures at the antiferromagnetic state, powder neutron diffraction measurements have been performed at 10 K and room temperature. Both the compounds have the G-type magnetic structure in which terbium atoms are antiferromagnetically coupled with the six neighbouring terbium atoms.

Magnetic properties of perovskite-type compounds La1−xSrxCrO3(x=0, 0.05, 0.10, 0.15, 0.20, and 0.25) have been reported. Their DC magnetic susceptibilities were measured from 4.5 K to 320 K. All these compounds showed an antiferromagnetic transition and their Neel temperatures decreased linearly from 286 K for LaCrO3with increasing Sr substitution. Below the Neel temperatures, other two magnetic transitions were furthermore observed for almost all the compounds. Below the Neel temperatures, all the compounds except LaCrO3showed magnetic hysteresis. The initial magnetization curve indicates the existence of the metamagnetic property below 20 K. Powder neutron measurements were performed at room temperature, 250 K and 50 K for La0.85Sr0.15CrO3. It was found that the crystal phase and magnetic transition occurred between 50 K and 250 K. The crystal structure at 250 K is rhombohedral with space groupR 3 c, and it transforms to an orthorhombic structure with space groupPnmaat 50 K. The magnetic structures at 50 K and at 250 K are both theG-type. The direction of magnetic moments is directed to [111] of the rhombohedral unit cell at 250 K and changes to be parallel to thez-axis of the orthorhombic unit cell (Pnma) at 50 K.

The magnetic properties of KUO 3 with the cubic perovskite structure have been studied. It shows an antiferromagnetic-type of transition at ca. 17 K in the magnetic susceptibility vs. temperature curve. Magnetic hysteresis is observed at 4.5 K, but not observed at 20 K. Neutron diffraction measurements have been performed on the powdered KUO 3 below and above the transition temperature. The neutron diffraction pattern measured at 10 K shows no appreciable difference from that measured at 50 K. A small ordered magnetic moment of U 5+ ion will make it very difficult to observe magnetic diffractions, even if a magnetic ordering occurs. If the magnetic spin alignment occurs in a small domain, no magnetic diffraction will be found in the neutron experiments. On the other hand, the magnetic phenomena of KUO 3 have been analyzed on the basis of an octahedral crystal field model.

Neutron diffraction and X-ray absorption measurements were carried out for a perovskite ferromagnet, CaMn0.6Ru0.4O3. While a previous X-ray diffraction had shown an orthorhombic Pnma structure, the present neutron diffraction at room temperature provided a better result for monoclinic P21/n. The analysis for the pattern at 4 K was consistent with the ferro- and antiferromagnetic phase separation at low temperatures. An X-ray absorption spectrum at the Ru–K edge showed that the valence of Ru is higher than 4+, which supports the proposed valency effect.

ZrNiAl alloy was found to absorb hydrogen up to a composition of ZrNiAlH0.53 in the measurement of a pressure-composition isotherm at 313 K. The structure parameters of the alloy and its hydride (deuteride) were refined by the Rietveld method using X-ray and neutron diffraction data. Both the alloy and deuteride have the Fe2P-type structure (space group: P62m; a = 6.9152(6)A and c = 3.4703(4)A for the alloy; a = 6.7225(7)Aandc = 3.7713(6)A for the deuteride). Hydrogenation leads to the lattice-contraction of the a axis by 2.8% and the lattice-expansion of the c axis by 8.7%. Neutron Rietveld refinement revealed that deuterium occupies a trigonal-bipyramidal site surrounded by three Zr and two Ni atoms.

The structure parameters of Ba4CaCu2O6 + δCO3 were refined by Rietveld analysis of angle-dispersive neutron powder diffraction data. The stoichiometric metal composition was confirmed by X-ray microanalysis. Iodometry showed that the amount of excess oxygen, δ, was nearly zero. The carbon content and infrared absorption spectrum of the compound gave evidence for the inclusion of CO32− ions in its crystal lattice. Ba4CaCu2O6CO3 is tetragonal with the P4/mmm space group and lattice parameters of a = 5.7879(2) A and c = 8.1409(3) A . Ba atoms occupy positions corresponding to the A site in ABO3 whereas Ca, Cu and C atoms are located at positions corresponding to the B site. Two copper sites are contained in the structure of Ba4CaCu2O6CO3: Cu(1) and Cu(2). If weak bonds between the Cu atoms and O atoms in the CO32− ion are neglected, Cu(1) and Cu(2) are taken as coordinated to four O(1) atoms and two O(2) atoms, respectively. Bond-valence sum calculations showed that the oxidation state of Cu is 2.48 for Cu(1) and 1.66 for Cu(2). The splitting and large thermal parameters of O atoms contained in the CO32− ion revealed its highly disordered orientation.

The magnetic properties of KUO 3 with the cubic perovskite structure have been studied. It shows an antiferromagnetic-type of transition at ca. 17 K in the magnetic susceptibility vs. temperature curve. Magnetic hysteresis is observed at 4.5 K, but not observed at 20 K. Neutron diffraction measurements have been performed on the powdered KUO 3 below and above the transition temperature. The neutron diffraction pattern measured at 10 K shows no appreciable difference from that measured at 50 K. A small ordered magnetic moment of U 5+ ion will make it very difficult to observe magnetic diffractions, even if a magnetic ordering occurs. If the magnetic spin alignment occurs in a small domain, no magnetic diffraction will be found in the neutron experiments. On the other hand, the magnetic phenomena of KUO 3 have been analyzed on the basis of an octahedral crystal field model.

Magnetic properties of ordered perovskite-type compounds Sr 2 LnRuO 6 (Ln=Tb, Ho) are reported. Powder neutron diffraction measurements at 10 K, 25 K and room temperature were performed to investigate their crystal and magnetic structures. Both of these compounds are distorted perovskites with space group P 2 1 / n and a 1:1 ordered arrangement of Ln 3+ and Ru 5+ over the six-coordinate sites. Data collected at 10 K and 25 K show that they have a long range antiferromagnetic ordering involving both Ln 3+ and Ru 5+ . Each of these ions orders in a Type I arrangement. The direction of the magnetic moments is along the c -axis for Sr 2 HoRuO 6 , while it is canted by ca. 20° from the c -axis for Sr 2 TbRuO 6 . The magnetic susceptibility and specific heat measurements show the existence of magnetic transitions at 41 K for Sr 2 TbRuO 6 and at 36 K for Sr 2 HoRuO 6 . The field-dependence of the magnetization was measured and a small hysteresis loop was found below magnetic transition temperatures, indicating the existence of a weak ferromagnetic moment associated with the antiferromagnetism.

Powder neutron diffraction measurements were performed on an antiferromagnetic manganese sulfide BaLa2MnS5 at 7 and 100 K. This sulfide has a tetragonal nuclear structure with space group I/mcm. The neutron diffraction data at 7 K show a collinear antiferromagnetic structure (space group I) with a propagation vector k = (1/2, 1/2, 1/2). The magnetic moment of Mn2+ is estimated to be 4.21 μB and determined to lie in a parallel direction with the c-axis. The magnetic exchange constants, (2J1 + J2)/kB andJ3/kB, are estimated to be −6.6 K and 0.80 K, respectively, from the molecular field approximation.

Neutron diffraction and X-ray absorption measurements were carried out for a silver–lead oxide Ag5Pb2O6. The powder neutron diffraction patterns could be fitted to the trigonal P 3 ¯ 1 m structure, as was found by X-ray diffraction. From the bond-valence-sum (BVS) analysis, the valences of the Ag and Pb ions were estimated to be about 1+ and 3.7+, respectively. The X-ray absorption measurements indicated that the ionic state of Ag is close to 1+, while that of Pb stands between 3+ and 4+. The deviation of the valence of the Pb ion from 4+ suggests a contribution of Pb orbitals to the metallic conduction as well as the possible superconductivity of this material, consistently with a recent band-structure calculation.

Transport and magnetic measurements and structural and NMR studies have been carried out on (Pr1-yR'y)1-xAxCoO3 {R'=(rare earth elements and Y); A=(Ca, Ba and Sr)} at ambient pressure or under high pressure. The system exhibits a phase transition from a nearly metallic to an insulating state with decreasing temperature T, where the low spin (LS) state of Co3+ is suddenly stabilized. For y=0, we have constructed a T-x phase diagram at various values of the external pressure p. It shows that the (T, x) region of the low temperature phase, which is confined to a very narrow region around x=0.5 at ambient pressure, expands as p increases, suggesting that the transition is not due to an order-disorder type one. For the occurrence of the transition, both the Pr and Ca atoms seem to be necessary. The intimate relationship between the local structure around the Co ions and the electronic (or spin) state of Co3+ ions is discussed: For the smaller unit cell volume or the smaller volume of the CoO6 octahedra and for the larger tilting angle of the octahedra, the temperature of the transition becomes higher. The role of the carriers introduced by the doping of the A atoms, is also discussed. By analyzing the data of 59Co-NMR spectra and magnetic susceptibilities of Pr1-xCaxCoO3 the energy separations among the different spin states of Co3+ and Co4+ are roughly estimated., Comment: 15 pages, 15 figures, 2 tables, submitted to J. Phys. Soc. Jpn

${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{CoO}}_{3}$ showed a simultaneous metal-insulator and paramagnetic-paramagnetic spin-state transition of the first-order type at 90 K accompanied by a volume contraction by $\ensuremath{\sim}2%.$ Neutron diffraction analysis revealed that the volume contraction is mainly attributed to the tilting of ${\mathrm{CoO}}_{6}$ octahedra which causes a decrease in the Co-O-Co angle. The electron configurations were proposed to be localized ${t}_{2g}^{6}$ (trivalent Co) and ${t}_{2g}^{5}$ (tetravalent Co) in the low-temperature phase and itinerant ${t}_{2g}^{5}{e}_{g}^{0.5}$ in the high-temperature phase.

γ-Mn alloys containing Au have been examined by magnetic measurements and X-ray and neutron diffraction experiments. The 9 at% Au alloy has a face centered orthorhombic lattice with a = 3.853, b = 3.794 and c = 3.731 A at 11 K, and shows a non-collinear antiferromagnetic structure with 4 sublattices; the three-axis components of the magnetic moments are as follows: μ a = 0, μ b = 1.10 and μ c = 1.91 μ B . A revised phase diagram for γ-Mn(Au) alloy system with 8–16 at% Au is proposed.

We have made neutron diffraction experiments for Fe 7- x Mn x Ge 6 with x = 2 and 4 and Co 7- x Mn x Ge 6 with x = 3.25, which have the hexagonal hp 13-type structure. It is determined by the Rietvelt analysis for the nuclear reflection that the 1T 1 site is entirely occupied by Mn atoms and the 6T 2 site by Fe or Co atoms and excess Mn atoms. The magnetic reflection of Fe 3 Mn 4 Ge 6 corresponds to the collinear antiferromagnetism with alternating ferromagnetic layers in which the magnetic moments of the 1T 1 and 6T 2 sites are 2.5 and 1.8 μ B /(Mn or Fe) atom, respectively. Magnetic structures of the other alloys are quite complicated.