We investigate the unusual phase transitions in SrRuO3 and Sr0.5Ca0.5Ru1−xCrxO3 (x=0,0.05
and 0.1) employing x-ray diffraction, resistivity, magnetic studies and x-ray photoemission spectroscopy. Our results show the compounds undergo a crossover from itinerant ferromagnetism to
localized ferromagnetism. The combined studies suggest Ru and Cr be in the 4+ valence state. A
Griffith phase and an enhancement in Curie temperature (Tc) from 38 K to 107 K are observed with
Cr doping. A shift in the chemical potential towards the valence band is observed with Cr doping.
In the metallic samples, interestingly, a direct link between the resistivity and orthorhombic strain
is observed. We also observe a connection between orthorhombic strain and Tc in all the
samples. Detailed studies in this direction will be helpful to choose suitable substrate
materials for thin-film/device fabrication and hence manoeuvre its properties. In the
non-metallic samples, the resistivity is mainly governed due to disorder, electron-electron correlation effects and a reduction in the number of electrons at the Fermi level. The value of
the resistivity for the 5% Cr doped sample suggests semi-metallic behaviour. Understanding its
nature in detail using electron spectroscopic techniques could unravel the possibility of its utility
in high-mobility transistors at room temperature and its combined property with ferromagnetism
will be helpful in making spintronic devices.

We investigate the effect of sample preparation conditions on the link between the structural and physical properties of polycrystalline spin-orbit Mott insulator, Sr2IrO4. The samples were prepared in two batches. With the first batch prepared as per the commonly adopted procedure in literature and the second batch prepared adopting the same procedure as the first batch but with an additional annealing in vacuum. Interestingly, our results show that without change in the value of the Curie temperature (TC ), there occurs increase in the value of magnetization, resistivity, magneto-resistance (MR) and an increase in temperature range of stabilization of the canted antiferromagnetic structure. The temperature behaviour of the difference in the irreversible magnetization between the samples is in line with the difference in the Ir-O-Ir in-plane bond angle. At low temperatures, the conduction mechanism in the first batch of the sample is mainly governed by disorder while in the case of the other sample it is of Arrhenius type. The magneto-transport results have shown its strong link with the disorder and structural results. Although the nature and mechanism of the induced disorder needs to be investigated further, the present results throw light on the role of disorder and its connectivity between the structure and physical properties to understand its complex behaviours.

We investigate here the magnetic, transport, local structural and electronic properties of Co$_2$Mn$_1$$_-$$_x$Cr$_x$Al (x=0, 0.05, 0.1 and 0.2). Our results show that all the compounds stabilise in B2 phase and are ferromagnets. The results reveal disorder at the structural and magnetic levels. X-ray absorption near edge structure (XANES) analysis reveal signature of antisite disorder between Mn and Al atoms with equal ratio. The electronic structure calculations suggest enhancement in the half metallicity, localisation of electrons at the Fermi level and an increment in density of states (DOS) with doping. The combined results of electronic structure calculations and XANES studies suggest transfer of electrons to the Co site. The results of high temperature resistivity measurements suggest the conduction electrons are undergoing transition from delocalisation to weak localisation to activated behaviour with Cr doping. The extended x-ray absorption spectroscopic (EXAFS) analysis shows that the local structure around Mn atom is different from the global structure as obtained from the x-ray diffraction results.The behaviour of the edge region is in line with the trend as obtained from the compositional analysis. We observe link between the hybridisation of 3$\emph{d}$ like states at the Mn, Cr sites with that at the Co site and the transport properties. This could help in understanding the unusual decrement in the lattice parameter with doping. These results reveal the role of local structure in understanding the physical properties of such systems.