arXiv subjects

Sonu Namdeo

Publications and source records attributed to Sonu Namdeo.

3 recordsLinked to original sources

arXiv2017

Investigation of charge states and multiferroicity in Fe-doped h-YMnO3

Polycrystalline YMn1-xFexO3 (YMFO_x) (0 <= x <= 0.1) compounds have been prepared in single phase and characterized by synchrotron X-ray diffraction, X-ray absorption near edge spectroscopy, magnetization, and dielectric measurements. Iron-substitution in hexagonal YMnO3 causes intra-lattice changes exceeding those of the lattice cell. XANES provide mixed-valence Mn3+/Mn4+ and Fe4+ charge states in these manganites, consistent with the observed decrease of the effective magnetic moment with Fe-doping. Magnetization M(T) evidence antiferromagnetic (AFM) ordering of the specimens with little weak ferromagnetism, and the metrices of exchange interaction suppress with Fe-doping, attributed to the lengthening of the Mn-O planar bond lengths. Dielectric ε'(T) results showing highly doping-dependent anomaly at T_N indicate linear magneto-electric coupling.

cond-mat.mtrl-sci↗

arXiv2017

Disorder-Driven Spin-Reorientation in Multiferroic $h-YMn_{1-x}Fe_xO_3$

Magnetic structure evolution of multiferroic hexagonal $YMn_{1-x}Fe_{x}O_{3}$ (${x} = 0, 0.05,$ and $0.1$) has been studied by carrying out detailed temperature-dependent neutron diffraction at zero- and 5T-fields. Thermodynamic data confirm antiferromagnetic ordering at $T_{N}$ in all the compositions. Our sub-$T_{N}$ neutron diffraction results assign the magnetic structure of pure $YMnO_3$ to $Γ_{1}$ irreducible representation. Over the perturbative-doping range, the magnetic configuration changes via $Γ_{1}+Γ_{2}$ for $YMn_{0.95}Fe_{0.05}O_{3}$ on to $Γ_{2}$ for $YMn_{0.9}Fe_{0.1}O_{3}$, as the maiden compositional analogue of spin-reorientation; its occurrence in temperature-domain already reported for several manganites. Moreover, while the large thermal isostructural changes observed above ${T}_{N}$ are subdued in the ordered state, small alterations by the applied 5T-field are relatively uniform across, confirming strong magneto-elastic nature of the system. Decrease of the ordered magnetic moment ($μ_{ord}$) and planar magnetic frustration noted with Fe-doping is enhanced by the applied field, apparently through canting.

cond-mat.mtrl-sci↗

arXiv2014

Isostructural changes in h-YMnO3 by Fe-substitution: effects on multiferroicity

Iron-substitution in hexagonal YMnO3 causes isostructural intra-lattice changes exceeding those of the lattice cell, contrary to the effects of non-magnetic B-site dopants. Magnetization M(T) evidence antiferromagnetic (AFM) ordering of the specimens with little weak ferromagnetism, and the metrices of exchange interaction suppress with Fe-doping, attributed to the lengthening of the Mn-O planar bond lengths. Ferroelectric (FE) P-E hysteresis loops reflect subdued and conductive ferroelectricity with increased Fe-substitution, traced to the reduced polyhedral buckling. Dielectric ε'(T) results showing highly doping-dependent anomaly at the Néel temperature signify strong magnetostrictive tunability and imply linear magneto-electric (ME) coupling. We recognize a correspondence of the structure-property changes versus Fe-doping, with the reported magnetostrictive effects upon cooling below TN. Correlations of AFM-FE-ME properties with their relevant microstructural attributes underline the spin-lattice-dipole coupling and provide significant characteristic figures.

cond-mat.str-el↗