Abstract:
This thesis is in two parts: First part relates to tuning of the granular magneto-resistance
(MR), which naturally occurs in systems consisting of ferromagnetic (FM) metallic grain
and antiferromagnetic (AFM)/ insulating grain boundary(GB).We have explored Ni-NiO
system with varying grain size and morphology. Magneto-resistance (MR) measurements
on various samples have been made using standard four probe resistivity technique. Low
eld MR data shows an anomaly at 250 K in Ni-NiO sample with crystalline hexagonal Ni
plates. This is likely to be due to the variations in the grain size as well as the magnetic
interactions between the FM grain and the AFM GB.
In second part of thesis, synthesis, characterization and magnetization measurements
on a relatively unexplored layered 4d magnetic oxide, SrRu2O6 are presented. Graphene
like 2-D sheets of this oxide have been obtained using the technique of "Liquid Exfoliation"
for the rst time. Same technique has also been employed to obtain 2-D sheets of
Na2IrO3 as well. Preliminary measurements reveal micron sized sheets in case of SrRu2O6,
and nano scale rectangular sheets in case of Na2IrO3 with signi cant yield. Exfoliation
process in these two samples has been checked for reproducibility and yield factor for
multiple times. Further experiments are required to obtain the layer thickness and composition
in each case. Thermo-remnant magnetization (TRM) data on the bulk samples
show nite remanence which hints toward the possibility of magneto-strictive e ects in
both the systems.
