Correlation between lattice vibrations with charge, orbital, and spin ordering in the layered manganite Pr 0.5 Ca 1.5 MnO 4 (original) (raw)
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Electronic self-organization in the single-layer manganite $ rm Pr_{1-x}Ca_{1+x}MnO4$
Phys Rev Lett, 2009
We use neutron scattering to investigate the doping evolution of the magnetic correlations in the single-layer manganite Pr1−x Ca1+x MnO4, away from the x = 0.5 composition where the CE-type commensurate antiferromagnetic (AF) structure is stable. We find that short-range incommensurate spin correlations develop as the system is electron doped (x < 0.5), which coexist with the CE-type AF order. This suggests that electron doping in this system induces an inhomogeneous electronic self-organization, where commensurate AF patches with x = 0.5 are separated by electron-rich domain walls with short range magnetic correlations. This behavior is strikingly different than for the perovksite Pr1−x Cax MnO3, where the long-range CE-type commensurate AF structure is stable over a wide range of electron or hole doping around x = 0.5.
Proceedings of the National Academy of Sciences, 2007
We use neutron scattering to study the lattice and magnetic structure of the layered half-doped manganite Pr0.5Ca1.5MnO4. On cooling from high temperature, the system first becomes chargeand orbital-ordered (CO/OO) near TCO = 300 K and then develops checkerboard-like antiferromagnetic (AF) order below TN = 130 K. At temperatures above TN but below TCO (TN < T < TCO), the appearance of short-range AF spin correlations suppresses the CO/OO induced orthorhombic strain, contrasting with other half-doped manganites, where AF order has no observable effect on the lattice distortion. These results suggest that a strong spin-lattice coupling and the competition between AF exchange and CO/OO ordering ultimately determines the low-temperature properties of the system.
Structural and magnetic properties of single layered manganite Pr0.5Ca1.5MnO4
Aps Meeting Abstracts, 2006
Using x-ray and neutron scattering, we have studied the structural and magnetic properties of the single-layer manganite La1−xSr1+xMnO4 (0 ≤ x < 0.7). Single crystals were grown by the travelingsolvent floating-zone method at 18 La/Sr concentrations. The low-temperature phase diagram can be understood by considering the strong coupling of the magnetic and orbital degrees of freedom, and it can be divided into three distinct regions: low (x < 0.12), intermediate (0.12 ≤ x < 0.45), and high (x ≥ 0.45) doping. LaSrMnO4 (x = 0) is an antiferromagnetic Mott insulator, and its spinwave spectrum is well-described by linear spin-wave theory for the spin-2 square-lattice Heisenberg Hamiltonian with Ising anisotropy. Upon doping, as the eg electron concentration (1 − x) decreases, both the two-dimensional antiferromagnetic spin correlations in the paramagnetic phase and the low-temperature ordered moment decrease due to an increase of frustrating interactions, and Néel order disappears above xc = 0.115(10). The magnetic frustration is closely related to changes in the eg orbital occupancies and the associated Jahn-Teller distortions. In the intermediate region, there exists neither long-range magnetic nor superstructural order. Short-range-correlated structural "nanopatches" begin to form above x ∼ 0.25. At high doping (x ≥ 0.45), the ground state of La1−xSr1+xMnO4 exhibits long-range superstructural order and a complex (CE-type) antiferromagnetic order which differs from that at low doping. The superstructural order is thought to arise from charge and orbital ordering on the Mn sites, and for x = 0.50 we conclude that it is of B2mm symmetry. For x > 0.50, the superstructural order becomes incommensurate with the lattice, with a modulation wavevector ǫ that depends linearly on the eg electron concentration: ǫ = 2(1 − x). On the other hand, the magnetic order remains commensurate, but loses its long-range coherence upon doping beyond x = 0.50.
Electronic self-organization in the single-layer manganite $ rm Pr_{ it 1-x}Ca_{ it 1+x}MnO_4$
Phys Rev Lett, 2009
We use neutron scattering to investigate the doping evolution of the magnetic correlations in the single-layer manganite rmPrit1−xCait1+xMnO4\rm Pr_{\it 1-x}Ca_{\it 1+x}MnO_4rmPrit1−xCait1+xMnO4, away from the x=0.5x=0.5x=0.5 composition where the CE-type commensurate antiferromagnetic (AF) structure is stable. We find that short-range incommensurate spin correlations develop as the system is electron doped ($x<0.5$), which coexist with the CE-type AF order. This suggests that electron doping in this system induces an inhomogeneous electronic self-organization, where commensurate AF patches with x=0.5x=0.5x=0.5 are separated by electron-rich domain walls with short range magnetic correlations. This behavior is strikingly different than for the perovksite rmPrit1−xCaitxMnO3\rm Pr_{\it 1-x}Ca_{\it x}MnO_3rmPrit1−xCa_itxMnO_3, where the long-range CE-type commensurate AF structure is stable over a wide range of electron or hole doping around x=0.5x=0.5x=0.5.
Electronic Self-Organization in the Single-Layer Manganite Pr1-xCa1+xMnO4
Physical Review Letters, 2009
We use neutron scattering to investigate the doping evolution of the magnetic correlations in the single-layer manganite Pr1−x Ca1+x MnO4, away from the x = 0.5 composition where the CE-type commensurate antiferromagnetic (AF) structure is stable. We find that short-range incommensurate spin correlations develop as the system is electron doped (x < 0.5), which coexist with the CE-type AF order. This suggests that electron doping in this system induces an inhomogeneous electronic self-organization, where commensurate AF patches with x = 0.5 are separated by electron-rich domain walls with short range magnetic correlations. This behavior is strikingly different than for the perovksite Pr1−x Cax MnO3, where the long-range CE-type commensurate AF structure is stable over a wide range of electron or hole doping around x = 0.5.
EPL (Europhysics Letters), 2012
The single layered manganite Pr0.22Sr1.78MnO4 undergoes structural transition from high temperature tetragonal phase to low temperature orthorhombic phase below room temperature. The orthorhombic phase was reported to have two structural variants with slightly different lattice parameters and Mn-3d levels show orbital ordering within both the variants, albeit having mutually perpendicular ordering axis. In addition to orbital ordering, the orthorhombic variants also order antiferromagnetically with different Néel temperatures. Our magnetic investigation on the polycrystalline sample of Pr0.22Sr1.78MnO4 shows large thermal hysteresis indicating the first order nature of the tetragonal to orthorhombic transition. We observe magnetic memory, large relaxation, frequency dependent ac susceptbility and aging effects at low temperature, which indicate spin glass like magnetic ground state in the sample. The glassy magnetic state presumably arises from the interfacial frustration of orthorhombic domains with orbital and spin orderings playing crucial role toward the competing magnetic interactions.
Charge and spin configurations in Pr 1-x Ca x MnO 3 (x=0.5-0.75)
Applied Physics A: Materials Science & Processing, 2002
Three perovskite systems Pr 1−x Ca x MnO 3 with x = 0.5, 0.67 and 0.75 have been investigated by neutron diffraction and completed with electron microscopy and physical measurements. The long range ordered superstructures of the Mn 3+ /Mn 4+ (1:1), (1:2) and (1:3) kinds have been solved consistently on the basis of powder data using a constrained refinement. PACS: 75.25.+z; 61.66.Fn
Physical Review B, 2008
Electronic-phase competition has been investigated for single crystals of half-doped bilayer-structure manganites, Pr͑Sr 1−y Ca y ͒ 2 Mn 2 O 7 ͑0 ഛ y ഛ 1.0͒, with controlled one-electron bandwidth ͑W͒. For y ഛ 0.4, the A-type antiferromagnetic ͑AF͒ state with x 2 − y 2 orbital order shows up as the ground state while accompanying the short-range vertical charge order with the periodicity of Ϸ4a 0 ͑a 0 Ϸ 0.4 nm͒. For y Ͼ 0.4, with reduced W, the CE-type AF state emerges with the ordered staggered orbitals ͑3x 2 − r 2 / 3y 2 − r 2 ͒ whose diagonal stripes undergo the 90°rotation with decreasing temperature, perhaps coupled with the evolution of spin correlation.
Physica B: Condensed Matter, 2021
In this paper, we present the spin-phonon coupling and dielectric response of nano-crystalline Pr 2 CoMnO 6 employing Raman and dielectric spectroscopic study. Pr 2 CoMnO 6 is a manganite compound , it undergoes a paramagnetic to ferromagnetic (PM-FM) phase transition around T c ∼172 K. Temperature-dependent Raman scattering experiment is carried out across T c to study the spin-phonon behavior in this material. The results from Raman study reveal an obvious softening of the phonon mode involving stretching vibrations of the (Co/Mn)O 6 octahedra in ferromagnetic temperature regions, indicating a close correlation between magnetism and lattice in Pr 2 CoMnO 6 and conform the spin phonon coupling. Further, we have carried out detailed study on dielectric response, impedance spectroscopy, electric modulus and AC conductivity of Pr 2 CoMnO 6 ceramics in the temperature range of 20 K-300 K and frequency range of 1kHz-5.5MHz. We found Pr 2 CoMnO 6 shows strong frequency dependence with large dispersion and large dielectric constant. It is found that thermally activated relaxation mechanism is involve and material is deviated from Debye's model which is confirmed by Nyquist plot and complex modules behavior.
Physical Review B, 2013
We study the temperature dependence as well as anisotropy of optical conductivity (σ 1 ) in the pseudocubic single crystal Pr 0.5 Ca 1.5 MnO 4 using spectrocopic ellipsometry. Three transition temperatures are observed and can be linked to charge-orbital (T CO/OO ∼320 K), two-dimensional-antiferromagnetic (2D-AFM) (∼200 K), and three-dimensional AFM (T N ∼125 K) orderings. Below T CO/OO , σ 1 shows a charge-ordering peak (∼0.8 eV) with a significant blue shift as the temperature decreases. Calculations based on a model that incorporates a static Jahn-Teller distortion and assumes the existence of a local charge imbalance between two different sublattices support this assignment and explain the blue shift. This view is further supported by the partial spectral weight analysis showing the onset of optical anisotropy at T CO/OO in the charge-ordering region (0.5-2.5 eV). Interestingly, in the charge-transfer region (2.5-4 eV), the spectral weight shows anomalies around the T 2D-AFM that we attribute to the role of oxygen-p orbitals in stabilizing the CE-type magnetic ordering. Our result shows the importance of spin, charge, orbital, and lattice degrees of freedom in this layered manganite.