arXiv subjects

S. Giri

Publications and source records attributed to S. Giri.

42 records · Page 3Linked to original sources

arXiv2007

Exchange bias with Fe substitution in LaMnO_3

The exchange bias (EB) in LaMn_{0.7}Fe_{0.3}O_3 is observed by the negative shift and training effect of the hysteresis loops, while the sample was cooled in external magnetic field. The analysis of cooling field dependence of EB gives the size of the ferromagnetic (FM) cluster ~ 25 Angstrom, where the magnetic anisotropy of FM cluster is found two order of magnitude higher than the FM bulk manganites. We propose that the nanoscale FM clusters are embedded in the glassy magnetic host with EB at the FM/glassy magnetic interface.

cond-mat.str-el↗

arXiv2007

A Conceptual DFT Approach Towards Developing New QSTR Models

Quantitative-structure-toxicity-relationship (QSTR) models are developed for predicting the toxicity (pIGC50) of 252 aliphatic compounds on Tetrahymena pyriformis. The single parameter models with a simple molecular descriptor, the number of atoms in the molecule, provide unbelievable results. Better QSTR models with two parameters result when global electrophilicity is used as the second descriptor. In order to tackle both charge- and frontier-controlled reactions the importance of the local electro (nucleo) philicities and atomic charges is also analyzed. Best possible three parameter QSTR models are prescribed.

physics.chem-ph↗

arXiv2006

An Atom Counting QSPR Protocol

A deceptively simple descriptor, viz. the number of carbon / non-hydrogenic atoms present in a molecule, is proposed for the development of useful quantitative-structure-property-relationship (QSPR) models. It is tested in models pertaining to the estimation of boiling point of alcohols, enthalpy of vaporization of polychlorinated biphenyls (PCBs), n-octanol / water partition coefficient of PCBs and chloroanisoles, pKa values of carboxylic acids, phenols and alcohols etc. Very high values of various regression coefficients (R2, R2CV, R2Ad) suggest the significance of this descriptor which further improves in the resulting two-parameter QSPR models with electrophilicity or its local variant as an additional descriptor.

physics.chem-ph↗

arXiv2006

Inhomogeneous phase separation and domain wall dynamics in the orthorhombically distorted La_{0.87}MnO_x

We observe the interesting magnetization and resistivity results in the orthorhombically distorted self doped manganite, La_{0.87}MnO_x. A significant irreversibility between zero-field-cooled and field-cooled resistivities as well as magnetization data is clearly observed up to a temperature which is well above the both paramagnetic to ferromagnetic (T_c) and metal to insulator transition (T_{MI}) temperatures. In the ferromagnetically ordered and metallic states the magnetotransport results suggest the influence of domain wall dynamics. Interesting scenario of memory effects through the domain wall dynamics is strikingly observed in the relaxation of resistivity in a limited temperature region. The characteristic features of magnetotransport behaviour are suggested duo to the co-existence of structurally driven inhomogeneous phase separation and domain wall dynamics.

cond-mat.str-el↗

arXiv2006

Magnetic field induced metastability in the self-doped manganites

We observe an interesting scenario of field induced metastabilities in the resistivity measurements. The resistivity exhibits a bifurcation of zero-field cooled and field-cooled (FC) temperature dependence below the paramagnetic to ferromagnetic transition ($T_c$). The clear evidence of {\it inverse} thermal hysteresis of resistivity is observed under FC condition in between 85 and 200 K, indicating the first order phase transition at $T_c$. The additional observation of minor hysteresis loops confirms the phase coexistence. The interesting features in the dynamics of resistivity is observed at 40 K, which is suggested due to the effect of domain wall dynamics.

cond-mat.str-el↗

arXiv2006

Interparticle interaction and size effect in polymer coated magnetite nanoparticles

Magnetization and Mossbauer studies have been performed on the polymer coated magnetite nanoparticles with particle size from 5.1 to 14.7 nm. The maximum in the temperature dependence of magnetization (TM) is found to be inconsistent with the particle size (DTEM). The effective magnetic anisotropy (Kan) is found to increase with the decrease of DTEM, which is attributed to the increase of surface anisotropy. The absence of coercivity and remanence of magnetization noticed well above TM indicates the superparamagnetic behaviour, which has also been observed in the temperature dependent Mossbauer results. The temperature dependence of hyperfine field is found to follow similar dependence of saturation magnetization for bulk magnetite.

cond-mat.mtrl-sci↗