Magnetoresistance studies of La2/3Sr1/3MnO3La_{2/3} Sr_{1/3} MnO_3 - YBa2Cu3O7YBa_2 Cu_3 O_7 - La2/3Sr1/3MnO3La_{2/3} Sr_{1/3} Mn O_3 trilayers with ferromagnetic coupling along the nodal direction of YBa2Cu3O7YBa_2 Cu_3 O_7

I have successfully prepared (110) trilayers of \LSMO-\YBCO-\LSMO. Magnetization measurements on these samples reveal a stronger coupling between the ferromagnetic layers. The coupling is an order of magnitude higher than that seen in the case of (001) trilayers. Magnetoresistance measurements show a first order transition in the data coinciding with the antiferromagnetic regime deduced from the magnetization measurements. I have also measured the anisotropic magnetoresistance (AMR) of these samples revealing an unusually high AMR ($\sim 72000$). I attribute such a high AMR to the pair breaking effects in these films.Comment: 12 pages, 7 figure

A comparative study of angle dependent magnetoresistance in [001] and [110] La2/3Sr1/3MnO3La_{2/3}Sr_{1/3}MnO_3

The angle dependent magnetoresistance study on [001] and [110] La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ thin films show that the anisotropy energy of [110] films is higher when compared with a [001] oriented La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ film of similar thickness. The data has been analyzed in the light of multidomain model and it is seen that this model correctly explains the observed behavior.Comment: 8pages, 2 figure

Nucleation of diamond films on heterogeneous substrates: a review

Diamond thin films are known to have properties similar to bulk diamond and have applications in both industry and fundamental studies in academia. The high surface energy of diamond makes it extremely difficult to grow diamond films on foreign substrates. Hence, to grow diamond films on non-diamond substrates, a nucleation step is needed. In this review various techniques used for diamond nucleation/seeding will be discussed. At present electrostatic seeding by diamond nanoparticles is the most commonly used seeding technique for nanocrystalline growth. In this technique the substrate is dipped in a nanodiamond solution to form a mono layer of diamond seeds. These seeds when exposed to appropriate conditions grow to form diamond layers. This technique is suitable for most substrates. For heteroepitaxial growth, bias enhanced nucleation is the primary technique. In this technique the substrate is biased to form diamond nuclei in the initial stages of growth. This technique can be used for any conducting flat surface. For growth on ceramics, polishing by diamond grit or electrostatic seeding can be used. Polishing the ceramics with diamond powder leaves small diamond particles embedded in the substrate. These small particles then act as seeds for subsequent diamond growth. Apart from these techniques, chemical nucleation, interlayer driven nucleation and mixed techniques have been discussed. The advantages and disadvantages of individual techniques have also been discussed

Superconducting nano-mechanical diamond resonators

In this work we present the fabrication and characterization of superconducting nano-mechanical resonators made from nanocrystalline boron doped diamond (BDD). The oscillators can be driven and read out in their superconducting state and show quality factors as high as 40,000 at a resonance frequency of around 10 MHz. Mechanical damping is studied for magnetic fields up to 3 T where the resonators still show superconducting properties. Due to their simple fabrication procedure, the devices can easily be coupled to other superconducting circuits and their performance is comparable with state-of-the-art technology.Comment: 5 pages 6 figures, Accepted for publication in Carbo

Growth of [110] La2/3_{2 / 3}Sr1/3_{1 / 3}MnO3_{3} - YBa2_{2}Cu3_{3}O7_{7} heterostructures

YBa$_{2}$Cu$_{3}$O$_{7}$ - La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ heterostructures of [110] orientation are grown to allow direct injection of spin polarized holes from the La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ into the CuO$_2$ superconducting planes. The magnetic response of the structure at T $<$ T$_{sc}$ shows both diamagnetic and ferromagnetic moments with [001] direction as magnetic easy axis. While the superconducting transition temperature (T$_{sc}$) of these structures is sharp ($\Delta$T$_{sc} \simeq$ 2.5 K), the critical current density (J$_c$) follows a dependence of the type $J_c = J{_o}(1-\frac{T}{T_{sc}})^{3/2}$ with highly suppressed J$_o$ ($\simeq 2 \times 10^4$ A/cm$^2$) indicating strong pair breaking effects of the ferromagnetic boundary.Comment: 12 pages five figure

Chemical mechanical polishing of thin film diamond

The demonstration that Nanocrystalline Diamond (NCD) can retain the superior Young's modulus (1,100 GPa) of single crystal diamond twinned with its ability to be grown at low temperatures (<450 {\deg}C) has driven a revival into the growth and applications of NCD thin films. However, owing to the competitive growth of crystals the resulting film has a roughness that evolves with film thickness, preventing NCD films from reaching their full potential in devices where a smooth film is required. To reduce this roughness, films have been polished using Chemical Mechanical Polishing (CMP). A Logitech Tribo CMP tool equipped with a polyurethane/polyester polishing cloth and an alkaline colloidal silica polishing fluid has been used to polish NCD films. The resulting films have been characterised with Atomic Force Microscopy, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. Root mean square roughness values have been reduced from 18.3 nm to 1.7 nm over 25 {\mu}m$^2$, with roughness values as low as 0.42 nm over ~ 0.25 {\mu}m$^2$. A polishing mechanism of wet oxidation of the surface, attachment of silica particles and subsequent shearing away of carbon has also been proposed.Comment: 6 pages, 6 figure

Correlation between incoherent phase fluctuations and disorder in Y1−x_{1-x}Prx_xBa2_2Cu3_3O7−δ_{7-\delta} epitaxial films from Nernst effect measurements

Measurements of Nernst effect, resistivity and Hall angle on epitaxial films of Y$_{1-x}$Pr$_x$Ba$_2$Cu$_3$O$_{7-\delta}$(Pr-YBCO, 0$\leq x\leq$0.4) are reported over a broad range of temperature and magnetic field. While the Hall and resistivity data suggest a broad pseudogap regime in accordance with earlier results, these first measurements of the Nernst effect on Pr-YBCO show a large signal above the superconducting transition temperature(T$_c$). This effect is attributed to vortex-like excitations in the phase incoherent condensate existing above T$_c$. A correlation between disorder and the width of the phase fluctuation regime has been established for the YBCO family of cuprates, which suggests a T$_c\approx$110K for disorder-free YBa$_2$Cu$_3$O$_{7-\delta}$.Comment: 5 pages, 6 figure