The non-magnetic and non-Fermi-liquid CaRuO3 is the iso-structural analog of the ferromagnetic (FM) and Fermi-liquid SrRuO3. We show that an FM order in the orthorhombic CaRuO3 can be established by the means of tensile epitaxial strain. The structural and magnetic property correlations in the CaRuO3 films formed on SrTiO3 (100) substrate establish a scaling relation between the FM moment and the tensile strain. The strain dependent crossover from non-magnetic to FM CaRuO3 was observed to be associated with switching of non-Fermi liquid to Fermi-liquid behavior. The intrinsic nature of this strain-induced FM order manifests in the Hall resistivity too; the anomalous Hall component realizes in FM tensile-strained CaRuO3 films on SrTiO3 (100) whereas the non-magnetic compressive-strained films on LaAlO3 (100) exhibit only the ordinary Hall effect. These observations of an elusive FM order are consistent with the theoretical predictions of scaling of the tensile epitaxial strain and the magnetic order in tensile CaRuO3. We further establish that the tensile strain is more efficient than the chemical route to induce FM order in CaRuO3.

We have deposited NdNi1−xMnxO3 (0 ≤ x ≤ 0.10) thin films on SrTiO3 (001), NdGaO3 (001), and YAlO3 (100) substrates and studied the effects of Mn-doping and strain on the charge transport. The majority of charge carriers are holes. Both the in-plane strain and the Mn-doping affect the electrical transport of the films. The metallic state completely vanishes at Mn-doping of x = 0.10. All the films, including x = 0, deposited on SrTiO3 are insulating throughout the temperature range. We find that the resistivity data of all the insulating films fit to two different models, i.e., variable range hopping and Arrhenius equation, in two different temperature regions. The mechanism of charge-transport in the insulating films changes from one type to another and the temperature range of fittings depend on the level of Mn-doping. The results and analyses clearly show that there are contrasting effects of Mn-doping in the metallic and the insulating regions: on one hand, the resistivity increases with increasing Mn-doping in the metallic region; and on the other hand, the hopping/activation of charge carriers get promoted in the insulating region.

No abstract

This paper reports on the steady state and transient photoconductivity of Ge20Se70−xIn10Bix (x = 2, 4, 6, 8, 10) thermally evaporated thin films. The dark conductivity (σd) increases with the increase in the Bi content. The value of σd increases slowly from x = 2 to x = 6, but for x ⩾ 8 the increase is quite abrupt. Photoconductivity (σph) also increases with the increase in the Bi content. The dark activation energy (ΔEd) decreases with the increase in the Bi content. There is a drop in the photosensitivity (σph/σd) of films with the increase in Bi addition. The result of the intensity dependent steady state photoconductivity (σph) follows the power law with intensity (F), i.e. σph α Fγ where the value of γ is close to 0.5, suggesting the predominance of bimolecular recombination in these materials. The rise and decay of photocurrent show the increase in the differential lifetime (τd), with the increase in the Bi content, indicating a delay in the recombination rate of photo-generated charge carriers. This change is governed by the photo-generated carriers trapped in the intrinsic defects or light induced defect creation through structural changes. One can therefore also expect that the density of states increases with the increase in the Bi content in amorphous thin films. The dispersion parameter (α) of the localized state energy distribution, determined from the decay curves, is also reported.

We have fabricated multilayer structure of half-metallic ferromagnet La0.7Sr0.3MnO3 and insulator-metal transition system NdNiO3 on SrTiO3 (100) substrate; thin layers of the former are intercalated in the major matrix of the later. The two structures exhibit pseudomorphic structural coupling with each other. We show that a large increase in the conductivity and an enhanced irreversibility across insulator-metal transition of NdNiO3 may be realized by varying the thickness of La0.7Sr0.3MnO3 and the ratio of thickness of the two layers. Corroborated by the magnetization data, it is shown that the combined effect of structure and magnetism by interfacial coupling is a much better technique than the chemical modification to control the electrical transport of NdNiO3.