C.L. Prajapat

Magnetic and dielectric behavior in YMn1−xFexO3 (x ≤ 0.5)

The role of doping Fe on the structural, magnetic, and dielectric properties of frustrated antiferromagnet YMn1−xFexO3 (x ≤ 0.5) has been investigated. The neutron diffraction analysis shows that the structure of these polycrystalline samples changes from hexagonal phase (space group P63cm) to orthorhombic phase (space group Pnma) for xu2009>u20090.2. The frustration parameter decreases with Fe substitution. All the compounds are antiferromagnetic, and the magnetic structure is described as a mixture of Γ3 and Γ4 irreducible representation (IR) in the hexagonal phase, and the ratio of these two IRs is found to vary with Fe doping (xu2009≤u20090.2). A continuous spin reorientation as a function of temperature is observed in these samples. The magnetic ground state in the orthorhombic phase of the higher doped samples (xu2009≥u20090.3) is explained by taking Γ1 (GxCyAz) representation of Pnma setting. In YMnO3 suppression of dielectric constant e′ is observed below TN indicative of magnetoelectric coupling. This anomalous behavior...

Structural investigations on Co3-xMnxTeO6; (0 < x ≤ 2); High temperature ferromagnetism and enhanced low temperature anti-ferromagnetism

In the quest of materials with high temperature ferromagnetism and low temperature anti-ferromagnetism, we prepare Co3-xMnxTeO6; (0u2009<u2009xu2009≤u20092) solid solutions. Room temperature structural investigations on these solid solutions as a function of Mn concentration using Synchrotron X-ray diffraction (SXRD) and X-ray absorption near edge structure measurements in corroboration with magnetism are presented. Phase diagram obtained from Rietveld Refinement on SXRD data as a function of Mn concentration indicates doping disproportionate mixing of both monoclinic (C2/c) and rhombohedral (R 3¯) structure for xu2009<u20090.5, while only R 3¯ structure for xu2009≥u20090.5. Further, it shows increase in both lattice parameters as well as average transition metal-oxygen (Co/Mn-O) bond lengths for xu2009≥u20090.5. Co and Mn K-edge XANES spectra reveal that both Co and Mn are in mixed oxidation state, Co2+/Mn2+ and Co3+/Mn3+. Relative ratios of Co3+/Co2+ and Mn3+/Mn2+ obtained using Linear combination fit decrease with increasing x (for xu2009≥u20090.5)....

Phase separated behavior in yttrium doped CaMnO3

Abstract The effect of electron doping on the structural, transport, and magnetic properties of Mn (IV)—rich Ca 1−x Y x MnO 3 (xxa0≤xa00.2) samples have been investigated using neutron diffraction, neutron depolarization, magnetization and resistivity techniques. The temperature dependence of resistivity follows the small polaron model and the activation energy exhibits a minimum for xxa0=xa00.1 sample. A phase separated magnetic ground state consisting of ferromagnetic domains (∼7xa0μm) embedded in G-type antiferromagnetic matrix is observed in the sample, xxa0=xa00.1. The transition to the long-range magnetically ordered state in this sample is preceded by a Griffith’s phase. On lowering temperature below 300xa0K a structural transition from orthorhombic structure ( Pnma ) to a monoclinic structure ( P2 1 /m ) is observed in the case of xxa0=xa00.2 sample. The ferromagnetic behavior in this case is suppressed and the antiferromagnetic ordering is described by coexisting C-type and G-type magnetic structures corresponding to the monoclinic and orthorhombic phases, respectively.

SEM, magnetization and Mössbauer spectroscopic characterization of Fe-U sequestration

The Jekyll and Hyde nature of iron and uranium loaded “IN-HOUSE’ resin viz., Polyacrylamide hydroxamic acid (PAAHA) has been characterized by FT-IR, SEM, Mossbauer spectroscopy, EDXRF and magnetization measurements techniques. Among all Mossbauer spectra and magnetization properties indicates supportive documents of characteristic special acquaintance nature of iron w.r.t accumulated U within the matrix even after loading of Fe in vast.

Investigation of magnetic properties for Hf 4+ substituted CeO 2 nanoparticles for spintronic applications

The single phase HfxCe1−xO2 (xu2009=u20090.01, 0.05 and 0.1) nanoparticles were produced via microwave refluxing technique. The substitution of Hf-ions into CeO2 lattice has been demonstrated by X-ray diffraction and transmission electron microscopy analyses. X-ray photoelectron spectroscopy analysis indicated that Ce was present in +u20093 and +u20094 states whereas Hf in +u20094 state. Raman, UV–Vis and photoluminescence spectroscopic analyses revealed the formation of surface defects including oxygen vacancies in the samples. The estimated defect concentration was 1.09u2009×u20091021, 1.32u2009×u20091021 and 1.49u2009×u20091021 cm−3 for xu2009=u20090.01, 0.05 and 0.1 samples respectively. The room temperature ferromagnetic behavior for the samples originate from the surface oxygen vacancies. The prevalence of ferromagnetic clusters considerably raised the MS value for xu2009=u20090.05 sample. The augmentation in the MS values with increased Hf concentration could be attributed to the increase in the defect concentration.