Structure Of Pr Research Articles

High pressure effect on the crystal and magnetic structure of Pr0.1Sr0.9MnO3 manganite

The crystal and magnetic structure of Pr0.1Sr0.9MnO3 manganite has been studied by the neutron diffraction at high pressures up to 5 GPa in the temperature range 10–295 K. At normal pressure and decreasing temperature the appearance of the C-type (TN = 220 K) and G-type (TN = 180 K) antiferromagnetic states occurs, which is accompanied by a structural phase transition from the cubic structure (Pm\( \bar 3 \)m space group) to the tetragonal structure (I4/mcm space group). It is shown that the temperature of the transition to the C-type antiferromagnetic phase increases with pressure with the pressure coefficient dTN/dP = 4.0(5) K/GPa and the temperature of the transition to the G-type antiferromagnetic phase weakly depends on pressure.

Magnetic Structures of ${\hbox {Pr}}_{0.8}{\hbox {Lu}}_{0.2}{\hbox {Mn}}_{2}{\hbox {Ge}}_{2}$ and ${\hbox {Pr}}_{0.6}{\hbox {Lu}}_{0.4}{\hbox {Mn}}_{2}{\hbox {Ge}}_{2}$

The magnetic structures of Pr0.8Lu0.2Mn2Ge2 and Pr0.6Lu0.4Mn2Ge2 have been determined by neutron powder diffraction over the temperature range 10-450 K. On cooling from the paramagnetic region the Mn sublattice of Pr0.8Lu0.2Mn2Ge2 orders in a similar manner to PrMn2Ge2 with first ab-plane intralayer antiferromagnetism (AFl) below TNintra ~ 397 K followed by canted ferromagnetism (Fmc) at TCinter ~ 330 K and then a conical (Fmi) spin structure below Tc/c ~ 192 K. The transition at TCPr=35 K with related enhancement in magnetization, is assigned to the additional ferromagnetic contribution of the Pr sublattice leading to the combined (Fmc+F(Pr)). For Pr0.6Lu0.4Mn2Ge2 the transition from PM to AFl occurs at TNintra ~ 375 K while the canted ferromagnetic (Fmc) state forms at TCinter ~ 321 K . The increased Lu concentration of Pr0.6Lu0.4Mn2Ge2 destroys the incommensurate Fmi conical spin structure of Pr0.8Lu0.2Mn2Ge2. Rather, in common with similar mixed RT2X2 systems (e.g., La1-xYxMn2Si2, La1-xPrxMn2Si2), the Pr0.6Lu0.4Mn2Ge2 compound exhibits co-existence of the AFmc and Fmc phases on cooling from the pure Fmc state. Transformation to the combined ferromagnetic state (Fmc+F(Pr)) takes place on c-axis ordering of the Pr sublattice at TCPr ~ 31 K . In the region of phase co-existence, the Fmc unit cell is larger than the AFmc unit cell indicating strong magneto-structural coupling with a change of the lattice inducing a change of the magnetic state.

Optical properties and structure of Pr3+-doped Al(PO3)3–LiF glasses as scattered neutron scintillator for nuclear fusion diagnostics

Scattered neutron diagnostics is an indispensable tool for both inertial confinement and magnetic confinement fusion research. For this purpose, a fast-response neutron scintillator with a high cross section for scattered neutrons is strongly required. Recently, based on our material design strategy, we have successfully developed the fast response time Pr3+-doped 20Al(PO3)3-80LiF glass scintillator for scattered neutron originated from inertial confinement fusion. The matrix glass 20Al(PO3)3-80LiF shows good glass forming ability, chemical durability and transparency in the deep ultraviolet region. The purpose of this work is to investigate the glass structure of 20Al(PO3)3-80LiF glasses using Raman spectroscopy and to discuss the relationship between physical and scintillation properties and glass structure.

High-pressure effects on the crystal and magnetic structure of Pr0.7Ca0.3MnO3

High-pressure effects on the crystal and magnetic structure of Pr_0.7Ca_0.3MnO₃

Thermoelectric properties of the Pr0.8Na0.2MnO3 manganite at ultrahigh pressures of up to 20 GPa

The pressure dependences of the thermopower and electrical resistance of the Pr0.8Na0.2MnO3 manganite are measured in the pressure range 0–20 GPa at room temperature. The thermopower varies nonmonotonically with pressure: the magnitude of the thermopower increases in the range of comparatively low pressures P < 5 GPa and decreases at higher pressures, whereas the electrical resistance decreases throughout the pressure range studied. The pressure at which the pressure coefficient dS/dP reverses sign is close to the value at which the Pr0.8Na0.2MnO3 manganite undergoes a magnetic phase transition in the low-temperature range. The correlation between the specific features in the behavior of the thermopower with variations in pressure and the transformations of the magnetic and crystal structures of Pr0.8Na0.2MnO3 at high pressures is discussed.

Valence band electronic structure ofPr1−xSrxMnO3 from photoemission studies

We have studied the charge carrier doping dependent changes in the valence band electronic structureof the Pr1−xSrxMnO3 system across the orbital ordered compositions using ultraviolet photoelectron spectroscopy. Thedx2−y2 orbital ordering is found to be causing an enhancement of the Mn 3d–O 2p hybridizationstrength and thereby the Mn 3d contribution to the subbands in the valence region. Ourphotoemission studies using different photon energies help in elucidating the nature andcomposition of the valence band features.

Subsolidus phase relations and crystal structures in the Pr1+xBa2−xCu3O7±δ system at 950 °C

Pr1+xBa2−xCu3O7±δ solid solution was investigated by means of X-ray powder diffraction and Rietveld analysis. Single-phase PrBa2Cu3O7±δ (Pr123) can be synthesized under a Pr-rich condition by sintering at 950 °C in air. The solubility of Pr1+xBa2−xCu3O7±δ solid solution is 0.08≤x≤0.80. The structure of Pr1+xBa2−xCu3O7±δ is orthorhombic for 0.08≤x&lt;0.30, and transforms into tetragonal for 0.30≤x≤0.80. To form single-phase Pr123, the Ba sites in the Pr123 structure are partially occupied by excess Pr ions, and the smallest amount of excess Pr is x=0.08. Meanwhile, all Ba ions stay in the Ba sites.

High pressure effects on the crystal and magnetic structure ofPr1−xSrxMnO3 manganites(x = 0.5–0.56)

The crystal and magnetic structures of the manganitesPr1−xSrxMnO3 (x = 0.5, 0.56) have been studied by means of powder neutron diffractionat high external pressures up to 4.8 GPa. At ambient pressure bothPr0.44Sr0.56MnO3 andPr0.5Sr0.5MnO3 have a tetragonalstructure (space group I4/mcm). At K in Pr0.44Sr0.56MnO3 the onset of A-type antiferromagnetic (AFM) state occurs, which is accompaniedby a structural phase transformation to the orthorhombic structure (spacegroup Fmmm). Pr0.5Sr0.5MnO3 at 175 K<T<TC = 265 K exhibits an intermediate tetragonal ferromagnetic (FM) phase followed by theonset of the orthorhombic A-type AFM phase at K. Under high pressure, in Pr0.44Sr0.56MnO3 a tetragonal C-type AFM phase ( K) appears and the phase separated state is formed, consisting of its mixturewith the initial orthorhombic A-type AFM phase ( K). In Pr0.5Sr0.5MnO3 the application of high pressure leads to a noticeable increase of the FM–A-type AFMtransition temperature from up to 230 K and formation of a phase separated state below 150 K, consisting ofa mixture of orthorhombic A-type AFM phase and tetragonal phase withoutlong range magnetic order. The stability of different magnetic states ofPr0.44Sr0.56MnO3 and Pr0.5Sr0.5MnO3 under high pressure is discussed.

Subsolidus phase relation and crystal structure in the Pr1+x-yBa2-x-zCay+zCu3O7�? system

The Pr1+xBa2-xCu3O7±δ solid solution was investigated by means of X-ray powder diffraction combined with Rietveld analysis. A Pr123 single phase could be synthesized under Pr-rich conditions by sintering at 950 °C in air. The solubility range of Pr1+xBa2-xCu3O7±δ solid solution is 0.08≤x≤0.80. The structure of Pr1+xBa2-xCu3O7±δ for 0.08≤x<0.30 is orthorhombic. The structure transforms into tetragonal for 0.30≤x≤0.80. To form the Pr123 single phase, the Ba sites in the Pr123 structure must have partial Pr ions, and the least amount is x=0.08. Ba ions cannot occupy the sites of Pr ions. In the Pr123 structure, Ca ions can replace Pr ions; the highest value is x=0.4 in the PrBa2-xCaxCu3O7±δ system under our experimental conditions. However, Ca ions cannot replace Ba ions. The ionic radius plays a more important role than the chemical properties in the substitution between Pr, Ba and Ca ions in the Pr123 structure.

The effects of film-substrate mismatch on Pr0.7Ca0.3MnO3thin films

Abstract The structures of Pr0.7Ca0.3MnO3 thin films on LaAlO3 (001) and NdGaO3 (001) substrates were investigated using transmission electron microscopy. These substrates induce a significant compressive strain and a slight tensile strain respectively on the film, and quite different microstructures were found in the two cases. Many complex tangles of dislocations were found in the film on LaAlO3, and it had a two-domain structure where both domains have a [110] axis perpendicular to the film plane. The film on NdGaO3 was mostly defect free, apart from occasional precipitates, which appeared to be NaCl-structure MnO, and displayed a single domain structure with the [001] axis perpendicular to the film. The difference in domain structure was explained on the grounds of misfit minimization, and the possible consequences of such a dependence of the domain structure on the substrate for the magnetic properties were discussed.