Indu Dhiman

Influence of A-site ionic radii on the magnetic structure of charge-ordered La 0.5 Ca 0.5 − x Sr x Mn O 3 manganites

The influence of the A-site ionic radii ( ) on the magnetic structure has been investigated in La0.5Ca0.5-xSrxMnO3 compounds (0 .GE. x .LE. 0.5) using neutron diffraction, magnetization, and resistivity techniques. All compounds in the composition range x .LE. 0.3 crystallize in the orthorhombic structure (Space Group Pnma). No further structural transition is observed as temperature is lowered below 300K. The compound x = 0.4, is a mixture of two orthorhombic phases crystallizing in Pnma and Fmmm space group. The x = 0.5 compound has a tetragonal structure in the space group, I4/mcm. The charge ordered (CO) state with CE-type antiferromagnetic order remains stable for x .LE. 0.3. Above x = 0.3, the CE-type antiferromagnetic state is suppressed. In x = 0.4 compound, A-type antiferromagnetic ordering is found at temperatures below 200K. Orbital ordering accompanying the spin ordering is found in all the samples with x .LE. 0.4. The system becomes ferromagnetic at x = 0.5 and no signature of orbital ordering is observed. As a function of , the charge ordered state is stable up to ~ 1.24A, and is suppressed thereafter. The magnetic structure undergoes a transformation from CE-type antiferromagnetic state to a ferromagnetic state with an intermediate A-type antiferromagnetic state.

Influence of B-site disorder in La0.5Ca0.5Mn1 − xBxO3 (B = Fe, Ru, Al and Ga) manganites

We have investigated the influence of B-site doping on the crystal and magnetic structure in La(0.5)Ca(0.5)Mn(1 - x)B(x)O(3) (B = Fe, Ru, Al and Ga) compounds using neutron diffraction, small angle neutron scattering, magnetization and resistivity techniques. The B-site doped samples are isostructural and possess an orthorhombic structure in the Pnma space group at 300 K. A structural transition from orthorhombic to monoclinic is found to precede the magnetic transition to the CE-type antiferromagnetic state in a few of these samples. On doping with Fe, the charge and orbitally ordered CE-type antiferromagnetic state is suppressed, followed by growth of the ferromagnetic insulating phase in 0.02 ≤ x ≤ 0.06 compounds. At higher Fe doping in x > 0.06, the ferromagnetic state is also suppressed and no evidence of long range magnetic ordering is observed. In Ru doped samples (0.01 ≤ x ≤ 0.05), the ferromagnetic metallic state is favored at T(C)≈200 K and T(MI)≈125 K and no significant change in T(C) and T(MI) as a function of Ru doping is found. In contrast, with non-magnetic Al substitution for 0.01 ≤ x ≤ 0.03, the charge ordered CE-type antiferromagnetic state coexists with the ferromagnetic metallic phase. With further increase in Al doping (0.05 ≤ x ≤ 0.07), both CE-type antiferromagnetic and ferromagnetic phases are gradually suppressed. This behavior is accompanied by the evolution of an A-type antiferromagnetic insulating state. Eventually, at higher Al doping (0.10 ≤ x ≤ 0.13), this phase is also suppressed and the signature of a spin glass like transition is evident in M(T). Likewise, substitution with Ga is observed to induce similar effects to those described for Al doped samples. The presence of short ranged ferromagnetic ordering has been further explored using small angle neutron scattering measurements in a few of the selected samples.

Structural, electrical, magnetic and microstructural behavior of the La0.7Sr0.3−xHgxMnO3 (0≤x≤0.3) system

We report a detailed investigation on the polycrystalline samples of the colossal magnetoresistance system La0.7Sr0.3−x Hgx MnO3 (0 x 0.3). The emphasis is put on identifying the role of Hg in the perovskite matrix. We have used the neutron diffraction technique for structural analysis. The issues pertaining to composition-dependent variations in parameters like average ionic radii, tolerance factor, variance, bond length, bond angle, lattice parameters and cationic vacancies have been addressed. The low temperature resistivity measurement and subsequent curve fitting are used to explore the contributions from various disorders and interactions. The samples with x = 0.3 composition showed distinct electrical behavior and magnetoresistance up to 46% around T = 198 K. The low temperature neutron diffraction data revealed ferromagnetic character of the samples. All the samples displayed similar microstructures. The variations in the electrical and magnetic properties are attributed to origination from cationic disorders.

Pressure effects on the magnetic structure in La 0.5 Ca 0.5 − x Sr x MnO 3 ( 0.1 ≤ x ≤ 0.4 ) manganites

The effect of high pressure (0\char21{}8 GPa) on the magnetic structure of polycrystalline samples of

Diffuse neutron scattering study of magnetic correlations in half-doped La0.5Ca0.5-xSrxMnO3 manganites (x = 0.1, 0.3, and 0.4)

{\text{La}}_{0.5}{\text{Ca}}_{0.5\ensuremath{-}x}{\text{Sr}}_{x}{\text{MnO}}_{3}

The dielectric response of La0.5Ca0.5−xSrxMnO3(0.1≤x≤0.4) manganites with different magnetic ground states

(0.1\ensuremath{\le}x\ensuremath{\le}0.4)

Neutron powder diffraction study and magnetic properties in LaMn1−xCuxO3 (x=0.05, 0.10 and 0.15)

manganites at 5 K is investigated using neutron-diffraction technique. Application of pressure is found to modify the previously reported magnetic structure, observed under ambient conditions, in these compounds [I. Dhiman et al., Phys. Rev. B 77, 094440 (2008)]. In

Neutron powder diffraction studies and magnetic properties in Nd1−xKxMnO3 (x = 0.15 and 0.20) compounds

x=0.1

Effect Of Ionic Radii And Size Mismatch On Structural And Magnetic Properties Of La0.5Ca0.5−xSrxMnO3 (0.1⩽x⩽0.5)

composition, at 4.6(2) GPa and beyond,