Ground State Of Pr Research Articles

PrBi: Topology meets quadrupolar degrees of freedom

Novel materials incorporating electronic degrees of freedom other than charge, including spin, orbital or valley \textit{et al} have manifested themselves to be of the great interests and applicable potentials. Recently, the multipolar degrees of freedom have attracted remarkable attention in the electronic correlated effects. In this work, we systematically studied the transport, magnetic and thermodynamic properties of the topological semimetal candidate PrBi in the framework of crystalline electric field theory. Our results demonstrate the $\Gamma_3$ non-Kramers doublet as the ground state of Pr$^{3+}$ (4$f^2$) ions. This ground state is nonmagnetic but carries a non-zero quadrupolar moment $\langle\hat{O}_2^0\rangle$. A quadrupolar phase transition is inferred below 0.08 K. No obvious quadrupolar Kondo effect can be identified. Ultrahigh-field quantum oscillation measurements confirm PrBi as a semimetal with non-trivial Berry phase and low total carrier density 0.06 /f.u. We discuss the interplay between low carrier density and $4f^2$ quadrupolar moment, and ascribe the weak quadrupolar ordering and Kondo effect to consequences of the low carrier density. PrBi, thus, opens a new window to the physics of topology and strongly correlated effect with quadrupolar degrees of freedom in the low-carrier-density limit, evoking the need for a reexamination of the Nozi\`{e}res exhaustion problem in the context of multi-channel Kondo effect.

Pr-magnetism in the quasi-skutterudite compound PrFe2Al8

The intermetallic compound PrFe2Al8 that possesses a three-dimensional network structure of Al polyhedra centered at the transition metal element Fe and the rare earth Pr is investigated through neutron powder diffraction and inelastic neutron scattering in order to elucidate the magnetic ground state of Pr and Fe and the crystal field effects of Pr. Our neutron diffraction study confirms long-range magnetic order of Pr below K in this compound. Subsequent magnetic structure estimation reveals a magnetic propagation vector with a magnetic moment value of /Pr along the orthorhombic c-axis and evidence the lack of ordering in the Fe sublattice. The inelastic neutron scattering study reveals one crystalline electric field excitation near 19 meV at 5 K in PrFe2Al8. The energy-integrated intensity of the 19 meV excitation as a function of follows the square of the magnetic form factor of thereby confirming that the inelastic excitation belongs to the Pr sublattice. The second sum rule applied to the dynamic structure factor indicates only 1.6(2) evolving at the 19 meV peak compared to the 3.58 for free , indicating that the crystal field ground state is magnetic and the missing moment is associated with the resolution limited quasi-elastic line. The magnetic order occurring in Pr in PrFe2Al8 is counter-intuitive to the symmetry-allowed crystal field level scheme, hence, is suggestive of exchange-mediated mechanisms of ordering stemming from the magnetic ground state of the crystal field levels.

Site preferences for La and Pr in Nd2Fe14B permanent magnet: A first principles study

Using the first principles method, we studied the site preference and the magnetic ground state of rare-earth elements La and Pr doped Nd2Fe14B permanent magnet. It was found that the La preferred the f-site doping at low doping ratio (12.5 %) while the g-site was more favorable at high doping (25 %). For the Pr impurity, we observed the opposite behavior because the site preference was switched. In addition, the spin configuration also depended on the impurity type and concentration. An antiferromagnetic (AFM) type spin configuration was found at both lower and higher doping ratios of La. For the Pr impurity, at a lower doping ratio, the AFM spin configuration was still preserved. However, the ferromagnetic spin configuration was more stable at a high doping ratio. Through impurity-substitution energy calculations, we found that the La impurity preferred to enter into the 2:14:1 phase at low doping, but it favored the grain-boundary phase at high (25 %) doping ratio. On the other hand, we observed that the Pr always preferred the main phase for both low and high doping concentrations.

Low Temperature Magnetic Properties of Pr(Cu,Ga)13with Orbitally Degenerate Ground State

Magnetic susceptibility χ( T ) and the specific heat C ( T ) of a cubic compound Pr(Cu,Ga) 12.85 were measured at low temperatures down to 0.1 K. χ( T ) shows Curie–Weiss behavior down to ∼1 K and turns to saturate at lower temperatures. This behavior is best understood by assuming a Γ 5 magnetic triplet for the crystalline electric field ground state of Pr 3+ (4 f 2 , J =4). The C ( T ) data indicate a continuous releasing of the Γ 5 entropy below ∼12 K, with no evidence of a phase transition down to 0.1 K. At low temperatures below 0.5 K, a 141 Pr nuclear Schottky tail is found to develop in zero field, which can be ascribed to a hyperfine field from the Pr moment. The estimated Pr moment value (1.3 µ B ) is found to be significantly smaller than the full moment value of 2 µ B for the Γ 5 triplet, which is interpreted by fluctuating Pr moments in the ground state whose time scale is comparable to the Pr nuclear spin relaxation time. The analysis yields a large C / T value of 2.2 J/mol·K 2 at low tempera...

Intervalence charge transfer in perovskite titanates R 1/2Na 1/2TiO 3:Pr 3+ (R=La, Gd, Y, Lu)

The spectroscopic properties of R 1/2Na 1/2TiO 3:Pr 3+ (R=La, Gd, Y, Lu) are investigated in the temperature range 77–500 K and interpreted in the frame of the intervalence charge transfer (IVCT) model. The model allowed locating the ground state of Pr 3+ relative to the host fundamental bands with an accuracy of 0.1–0.2 eV.

Heavy-electron-like behavior in cubicPrCu4Au

The magnetization M(H),magnetic susceptibility χ(T), electrical resistivity ρ(T) and specific heat C(T) properties of PrCu4Au have been investigated. A clear antiferromagnetic transitionTN is observedat 2.5 K in C(T) and χ(T). The internal magnetic field at the Pr nucleus,HHF, is obtained to be 195 T from the nuclear specific heat observed inC(T) below 0.7 K. Theground state of Pr 4f2 in the cubic crystalline electric field is inferred to be a magnetic tripletΓ5 from the magnitude of the magnetization at 2 K, which coincides with the value of the4f2 magnetic momentsdeduced from HHF. The large value of the electronic specific heat coefficient,γ, remainsat the zero-temperature limit even in external magnetic fields. On the other hand, the entropy up toTN is somewhatless than Rln3. These anomalous heavy-electron-like behaviors probably originate in the fact that boththe magnetic moments and the quadrupole moments are involved in the ground state ofPr 4f2.

Electrical and Magnetic Properties of R3Al11 (R = La, Ce, Pr, and Nd)

High-quality single crystals of R 3 Al 11 (R = La, Ce, Pr, and Nd) with the La 3 Al 11 -type orthorhombic crystal structure (space group I m m m ) have been grown by the Al-flux method. For Ce 3 Al 11 , signatures for ferromagnetic and antiferromagnetic orderings at T C = 6.3 K and T N = 3.2 K, respectively, have been observed in the magnetic susceptibility, magnetization, specific heat, and electrical resistivity. An antiferromagnet Pr 3 Al 11 , on the other hand, exhibits two magnetic transitions at T N1 = 12.6 K and T N2 = 3.1 K. An antiferromagnet Nd 3 Al 11 also exhibits multiple magnetic transitions at T N1 = 13.2 K, T N2 = 9.4 K, T N3 = 2.9 K, and T N4 = 1.77 K in zero magnetic field. The transition at T N4 has a first-order character. The crystalline electric field (CEF) analysis of magnetic susceptibility, magnetization and specific heat data shows that the CEF splitting is larger for Ce 3 Al 11 than for Pr 3 Al 11 and Nd 3 Al 11 . The CEF ground state of Pr 3 Al 11 is a singlet. Magnetic order o...

Resistivity and Magnetoresistance of La-doped CeOs4Sb12and PrOs4Sb12

The resistivity and magnetoresistance of La-doped CeOs 4 Sb 12 and PrOs 4 Sb 12 were investigated at temperatures down to 20 mK and in magnetic fields up to 18 T. The resistivity of Ce 0.98 La 0.02 Os 4 Sb 12 , in fields smaller than 4 T, has a Kondo-hole impurity temperature variation, i.e., ρ=ρ 0 + A T 2 , with a negative and strongly field-dependent A . However, the positive magnetoresistance suggests that this anomalous behavior is due to Kondo-hole bands. The magnetoresistance of La-doped PrOs 4 Sb 12 confirms the singlet CEF ground state of Pr. Furthermore, its field variation and near isotropy argue against lowest-level crossing along any crystallographic direction. Instead, the results suggest avoided level crossing for all directions of the magnetic field. The possible origin of a dome-like shape in the magnetoresistance of the pure Pr compound is discussed.

A New Multipolar Ordering Compound, Rare-Earth Palladium Bronze PrPd3S4

Specific heat and magnetization measurements were performed on single crystalline PrPd 3 S 4 . A λ-type anomaly at T M = 1.56 K in the specific heat shifts to higher temperatures by magnetic fields, begins to shift to lower temperatures above 2 T, and disappears above 3.6 T. The 4 f ground state of Pr 3+ was deduced to be a magnetic triplet. Below T M , the magnetic susceptibility increases while no spontaneous magnetization appears. These results strongly reveal that PrPd 3 S 4 shows a multipolar ordering at T M . The most probable ordering state for PrPd 3 S 4 is an antiferroquadrupolar (AFQ) ordering since the B – T phase diagrams are of the “re-entrant” type, which is typical for AFQ ordering compounds.

Anomalous properties of PrMg 3 with the cubic Γ 3 ground state

The electrical resistivity ρ( T) has been measured on a single crystal of PrMg 3. PrMg 3 shows a Kondo-like broad anomaly in the specific heat C P ( T) at low T arising from multipole (quadrupole and octupole) degrees of freedom of the non-magnetic, non-Kramers Γ 3 doublet ground state of Pr 3+ ions. Observed non-Kondo-like behavior of ρ( T) is discussed in connection with similar behavior in closely related PrAg 2In, where we show that the characteristic band structure and the symmetry properties of the hybridization between conduction and f electrons can explain the seemingly contradictory behavior between C P ( T) and ρ( T).

Resonant X-ray scattering as a probe of the valence and magnetic ground state and excitations in Pr 0.6Ca 0.4MnO 3

X-ray resonant techniques have been used to study the ground state and electronic excitations of the perovskite Pr 0.6Ca 0.4MnO 3. We utilized resonant diffraction at the Mn K-edge as a contrast technique for determining the pattern of Mn atoms in inequivalent crystallographic sites. In order to determine the important properties of the 3d electrons in this system, we have probed the unoccupied 3d orbitals using the magnetic and non-magnetic soft X-ray diffraction at the Mn L-edges. Finally resonant inelastic X-ray scattering experiments have been performed at the Mn K-edge. This latter technique provides new insights into the ground state as it probes the elementary electronic excitations.

Magnetic Ground State of Pr0.89LaCe0.11CuO4+α-δwith Varied Oxygen Depletion Probed by Muon Spin Relaxation

The magnetic ground state of an electron-doped cuprate superconductor, Pr 1- x LaCe x CuO 4+α-δ ( x =0.11, α≃0.04), has been studied by means of muon spin rotation/relaxation (µSR) over a wide variety of oxygen depletion, 0.03 ≤δ≤0.12. The appearance of a weak random magnetism over the entire crystal volume has been revealed by a slow exponential relaxation. The absence of δ-dependence for random magnetism and a multiplet pattern of the muon Knight shift at higher fields strongly suggest that the random moments are associated with excited Pr 3+ ions under a crystal electric field.

Magnetic behaviour of the tetravalent praseodymium compoundSr2PrO4

We report on investigations of the magnetic properties of the tetravalent praseodymium(Pr4+)compound Sr2PrO4 by dc and ac magnetic susceptibility and heat capacity measurements.The compound shows signatures of long range magnetic order atTN = 3 K in the heat capacity and magnetization data. In addition, the temperature dependence ofthe field cooled and the zero-field cooled susceptibility is hysteretic below 10 K. Heat capacityversus temperature data show that a significant part of the magnetic entropy is released aboveTN.This reveals that short range magnetic correlations among the Pr moments exist well aboveTN.The magnetic entropy obtained from the heat capacity measurements indicates that onlythe crystal field ground state of Pr with effective spin- is significantly populated at low temperatures.

Magnetic Phase Diagram of the Heavy Fermion Superconductor PrOs4Sb12

We investigated the magnetic phase diagram of the first Pr-based heavy fermion superconductor PrOs 4 Sb 12 by means of high-resolution dc magnetization measurements in low temperatures down to 0.06 K. The temperature dependence of the magnetization M ( T ) at 0.1 kOe exhibits two distinct anomalies at T c1 =1.83 K and T c2 =1.65 K, in agreement with the specific heat measurements at zero field. Increasing magnetic field H , both T c1 ( H ) and T c2 ( H ) move toward lower temperatures without showing a tendency of intersecting to each other. Above 10 kOe, the transition at T c2 ( H ) appears to merge into a line of the peak effect which is observed near the upper critical field H c2 in the isothermal M ( H ) curves, suggesting a common origin for these two phenomena. The presence of the field-induced ordered phase (called phase A here) is confirmed for three principal directions above 40 kOe, with the anisotropic A-phase transition temperature T A : T A [100] > T A [111] > T A [110] . The present results are discussed on the basis of crystalline-electrical-field level schemes with a non-magnetic ground state, with emphasis on a Γ 1 singlet as the possible ground state of Pr 3+ in PrOs 4 Sb 12 .

X-ray measurement for the orbital ordering materials

By using our developed X-ray measurement system for powder sample below 1 K , we have studied the orbital ordering materials PrPtBi, Ce 0.75La 0.25B 6 and PrPb 3. The ground state of Pr 3+ ion in the cubic semiconductor compound PrPtBi, is a nonmagnetic Γ 3 doublet. To investigate whether the phase transition at 1.35 K is antiferro-quadrupolar (AFQ) or ferro-quadrupolar type ordering, we have studied this compound by X-ray measurement. Below the transition temperature we could not observe the splitting of any reflection lines but the full-width at half-maximum increases with decreasing temperature, which suggests the phase transition at 1.35 K is AFQ ordering. In this paper we also report the integrated intensity of (4 0 0) reflection as a function of temperature. This is the first experiment to investigate the AFQ ordering using ordinary X-ray diffraction method.

Magnetic properties of Pr 1− xLa xPtAl

Orthorhombic PrPtAl with a nonmagnetic singlet ground state of Pr 3+ is an induced-moment ferromagnet with T c=5.8 K. We have investigated the effect of La substitution of Pr by measurements of specific heat and magnetization of polycrystalline samples of Pr 1− x La x PtAl (0⩽ x⩽0.3). We have found that with increasing La concentration the reduction of the ordered Pr moment is much weaker in the orthorhombic singlet–singlet system Pr 1− x La x PtAl than in the cubic singlet–triplet system (Pr 1− x La x ) 3Tl.

Magnetic ground state of Pr in

Inelastic neutron scattering experiments were performed on to determine the magnetic ground state of the Pr ions. In this compound, superconductivity is suppressed by the presence of Pr ions. The magnetic ground state is found to be very similar to that in and . However, the high energy spectrum has a stronger resemblance to that of , where the Pr ions see a very similar local structure. Therefore, a similar set of higher order crystalline-electric-field parameters and an inversion of can explain qualitatively the neutron spectra. The suppression of superconductivity and the quasi-triplet magnetic ground state support models which correlate the unusual magnetic properties with suppression by Pr.

Formation of uniform magnetic structures and epitaxial hydride phases in Nd/Pr superlattices

The chemical and magnetic structures of neodymium/praseodymium superlattices grown by molecular-beam epitaxy have been determined using x-ray and neutron-diffraction techniques. The x-ray measurements show that the superlattices have a dhcp structure of high crystalline quality, and that the stacking sequence is coherent over many bilayer repeats. The neutron measurements show that for the hexagonal sites of the dhcp structure, the Nd magnetic order propagates coherently through the Pr, whereas the order on the cubic sites is either suppressed or confined to single Nd blocks. It is also shown that the singlet ground state of Pr is perturbed to produce a local moment on the hexagonal sites, so that in some cases there is a uniform magnetic structure throughout the superlattice. These results cast new light on the theory of magnetic interactions in rare-earth superlattices. Within a few months of growth these light rare-earth samples are found to react with hydrogen to form new single-crystal phases, which are coherent with the epitaxial structure.

The ground state of dilute Tm, Pr, and U systems is degenerate

The ground state of the appropriate generalization of the impurity Anderson model for valence fluctuations between two realistic configurations, is obtained in the atomic, narrow-band limit, using the Lanczos method. This limit describes the strong-coupling fixed point of renormalization group treatments for intermediate valence and Kondo impurities. The resulting ground state of Tm is highly degenerate and contains states of total angular momentum 0, 3 2 , 2, 5 2 , 4 and 9 2 . The ground state of Pr has J t = 15 2 and that of U has J t = 8. For Tm, the crystal electric field or and applied magnetic field should split the degeneracy favouring the magnetic states. In agreement with experiments in Tm and U compounds the magnetic moment at the impurity is in all cases anomalously small. It decreases when L- S coupling is replaced by intermediate coupling and vanishes in the limit of j- j coupling.

Incipient valence instability of dilute Pr in Pd

Abstract At 300 K the L III valence of dilute Pr in Pd is 3.10. At helium temperatures the susceptibility shows an effective moment close to the Γ 5 crystal field groundstate of Pr 3+ but with a characteristic temperature of 1.6 K which implies a nonmagnetic impurity groundstate. The impurity resistivity has a minimum and the thermopower a maximum at 20 K. Above 100 K the effective impurity moment is strongly enhanced by magnetic polarization of the Pd matrix.