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Geometrical frustration, arising from the unsatisfying magnetic bonds in peculiar magnetic materials, leads to the emergence of a variety of ground states ranging from exotic disordered (quantum spin liquid) to unusual magnetic ordered states. We have prepared and studied the magnetic properties of a novel quantum magnet PbCuTeO5, whose structure suggests that it has 2D distorted check-board lattice. A large antiferromagnetic Curie-Weiss temperature of -165 K and a spin freezing temperature Tf = 6 K are observed in the magnetic data. Our results suggest that PbCuTeO5 is a new frustrated quantum magnet with a large frustration parameter f = θCW/Tf 27. [ABSTRACT FROM AUTHOR]

Low temperature x-ray powder diffraction studies, in conjunction with transmission electron microscopy on stoichiometric (δ = 0.01) and oxygen deficient (δ =0.12) samples of La0.2Sr0.8MnO3-δ manganites have been carried out. These studies revealed that oxygen stoichiometry plays a key role in controlling ground state of electron doped manganites. It is observed that the La0.2Sr0.8MnO2.99 undergoes a first order phase transition from cubic (Pm-3m) to JT-distorted twin tetragonal (I4/mcm) phase associated with ~-type antiferromagnetic ordering at ~260K. This JT-distortion induced cubic to tetragonal phase transition get totally suppressed in La0.2Sr0.8MnO2.88. The basic perovskite lattice of the off-stoichiometric La0.2Sr0.8MnO2.99 remains cubic down to 80K but undergoes a well-developed charge-ordering transition with 9x9 modulations at ~260K. [ABSTRACT FROM AUTHOR]

Structural and electrical transport studies on polycrystalline self-doped Pr1-xMnO3±d (with x=0, 0.1& 0.125) have been done using XRD and low-temperature resistivity measurement. The results of the Rietveld refinement of XRD data show that all these compounds crystallize in an orthorhombic structure with Pnma space-group. With increasing A-site vacancies, the unit cell volume decrease and lattice parameters undergo non monotonous change. The electrical transport studies reveal insulating behaviour with small polaron hopping above TC and a kink corresponding to canted-antiferromagnetic spin ordering. [ABSTRACT FROM AUTHOR]

The temperature (T) dependent x-ray diffraction (XRD) and resistivity measurements of La0.175Pr0.45Ca0.375MnO3-δ (LPCMO) have been performed down to 2K to understand the structural and transport properties. From room temperature down to 220K, LPCMO exists in orthorhombic phase with Pnma structure and at T~220K, it transforms to charge ordered (CO) monoclinic phase with P21/m structure and remains as it is down to 2K. The CO phase is evident from the occurrence of weak but well defined superlattice peaks in the XRD pattern. This structural transformation is of first order in nature as evident from the phase coexistence across the transition region. These results thus clearly illustrate that LPCMO undergoes a first order structural phase transition from charge disordered orthorhombic phase to CO monoclinic phase at 220K, consistent with temperature dependent resistivity results. Our structural analysis of T dependent XRD data using Rietveld refinement infers that below 220K, LPCMO forms commensurate CO monoclinic P21/m structure with four times structural modulation. [ABSTRACT FROM AUTHOR]

Low-temperature XRD and dielectric studies of Sr1-xCaxTiO3 (SCT) (x=0.27 and 0.30) shows paraelectric (PE) P21212 to antiferroelectric (AFE) Pbcm phase-transitions. Analysis of the XRD data reveals that the phase transition appears due to anti-parallel alignment of the ionic dipoles formed by non-centrosymetric shift of the Ti+4 and O-2 ions in the lattice. Analogous to antiferromagnetic (AFM) interaction, AFE interaction is also expected to get suppressed under applied DC electric field. In-field dielectric studies reveal low-temperature shift of the PE-AFE transition temperature. A sufficiently high-field is expected to cause metastable ferroelectricity in it. [ABSTRACT FROM AUTHOR]

The temperature dependent structural studies on the polycrystalline La0.70Bi0.30CrO3 have been done using XRD and TEM. The results of the Reitveld refinement of XRD data and diffraction patterns of TEM confirm that it crystallizes in an orthorhombic structure with Pnma space-group and remains Pnma down to 80K. With decreasing temperature lattice parameters and cell volume decreases linearly with temperature. [ABSTRACT FROM AUTHOR]

Using low-temperature (LT) XRD and resistively vs temperature data we show that the evolution of the ferromagnetic state LaMnO3±δ is accompanied by the structural distortion, which is evident from the change is the FWHM of (220) peak of R-3c phase at TC. The crystal structure gets distorted at TC and regains its original form when the system completely transforms to a homogenous ferromagnetic phase (FM). Our results thus give a direct evidence of strong magneto-elastic coupling in these systems. [ABSTRACT FROM AUTHOR]

Magnetic and dielectric properties on a polycrystalline La0.7Bi0.3CrO3 have been investigated. A canted antiferromagnetic (CAF) phase transition giving weak ferromagnetism at TN = 230 K has been observed. M-H at 10 K shows non-saturating trend, even up to 5 T, confirms the CAF ordering. The permittivity ([variant_greek_epsilon]′)-vs-temperature (T) variation shows a relaxor ferroelectric (RFE) nature accompanied by a pronounced anomaly in [variant_greek_epsilon]′-T at TN. The anomaly in [variant_greek_epsilon]′-T at TN indicates the presence of magentoelectric (ME) coupling in this material. [ABSTRACT FROM AUTHOR]