arXiv subjects

Mohit Chandra

Publications and source records attributed to Mohit Chandra.

21 records · Page 2Linked to original sources

arXiv2019

Enhancement of magnetoelectric coupling in Cr doped Mn2O3

The effect of Cr doping with nominal compositions Mn2-xCrxO3 (0 less than equal to x less than equal to 0.10) has been undertaken to investigate its effect on structural, magnetic, dielectric and magnetoelectric properties. The Cr doping transformed the room temperature crystal structure from orthorhombic to cubic symmetry. Similar to alpha-Mn2O3, two magnetic transitions have been observed in the Cr doped samples. The effect of Cr doping is significant on the low temperature transition i.e. the lower magnetic transition shifted towards higher temperature (25 K for pristine to 40 K for x=0.10) whereas the high temperature transition decreases slightly with increasing Cr content. A clear frequency independent transition is observed in complex dielectric measurements for all compositions around high temperature magnetic ordering. Interestingly, the magnetodielectric behaviour enhanced enormously approx 21% with Cr substitution as compared to pristine Mn2O3.

cond-mat.mtrl-sci↗

arXiv2018

Exact Passive-Aggressive Algorithms for Learning to Rank Using Interval Labels

In this paper, we propose exact passive-aggressive (PA) online algorithms for learning to rank. The proposed algorithms can be used even when we have interval labels instead of actual labels for examples. The proposed algorithms solve a convex optimization problem at every trial. We find exact solution to those optimization problems to determine the updated parameters. We propose support class algorithm (SCA) which finds the active constraints using the KKT conditions of the optimization problems. These active constrains form support set which determines the set of thresholds that need to be updated. We derive update rules for PA, PA-I and PA-II. We show that the proposed algorithms maintain the ordering of the thresholds after every trial. We provide the mistake bounds of the proposed algorithms in both ideal and general settings. We also show experimentally that the proposed algorithms successfully learn accurate classifiers using interval labels as well as exact labels. Proposed algorithms also do well compared to other approaches.

cs.LG↗

arXiv2018

Multiferroicity and magnetoelastic coupling in alpha-Mn2O3: A binary perovskite

Multiferroics where at least two primary ferroic orders are present and coupled in a single system constitute an important class of materials. They attracted special consideration as they present both intriguing fundamental physics problems and technological importance for potential multifunctional devices. Here, we present the evidence of multiferroicity and magnetoelectric (ME) coupling in alpha-Mn2O3; a unique binary perovskite. Corresponding to the antiferromagnetic (AFM) ordering around 80K, a clear frequency independent transition is observed in the dielectric permittivity. We showed that electric polarization emerges near AFM regime that can be modulated with magnetic field. The detailed structural analysis using synchrotron radiation X-ray diffraction demonstrates the increase in structural distortion with decreasing temperature, as well as changes in the unit cell parameters and bond lengths across the ferroelectric and magnetic ordering temperatures. This observation of multiferroicity and magnetoelastic coupling in alpha-Mn2O3 provides insights for the exploration of ME coupling in related materials.

cond-mat.mtrl-sci↗