Effect of strain and electric field on the electronic soft matter in manganite thin films

We have studied the effect of substrate-induced strain on the properties of the hole-doped manganite (La$_{1-y}$Pr$_{y}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$ ($y$ = 0.4, 0.5 and 0.6) in order to distinguish between the roles played by long-range strain interactions and quenched atomic disorder in forming the micrometer-scale phase separated state. We show that a fluid phase separated (FPS) state is formed at intermediate temperatures similar to the strain-liquid state in bulk compounds, which can be converted to a metallic state by applying an external electric field. In contrast to bulk compounds, at low temperatures a strain stabilized ferromagnetic metallic (FMM) state is formed in the $y$ = 0.4 and 0.5 samples. However, in the $y$ = 0.6 sample a static phase separated (SPS) state is formed similar to the strain-glass phase in bulk compounds. Hence, we show that long-range strain interaction plays a dominant role in forming the micrometer-scale phase separated state in manganite thin films.Comment: 4 pages, 3 figures included, RevTeX, Submitted to PR

Competing `soft' dielectric phases and detailed balance in thin film manganites

Using frequency dependent complex capacitance measurements on thin films of the mixed-valence manganite (La$_{1-y}$Pr$_{y}$)$_{1-x}$Ca$_{x}$MnO$_{3}$, we identify and resolve the individual dielectric responses of two competing dielectric phases. We characterize their competition over a large temperature range, revealing they are in dynamic competition both spatially and temporally. The phase competition is shown to be governed by the thermodynamic constraints imposed by detailed balance. The consequences of the detailed balance model strongly support the notion of an `electronically soft' material in which continuous conversions between dielectric phases with comparable free energies occur on time scales that are long compared with electron-phonon scattering times.Comment: 8 pages, 7 figure

Collapse of the charge ordering gap of Nd_{0.5}Sr_{0.5}MnO_{3} in an applied magnetic field

We report results of tunneling studies on the charge ordering compound Nd_{0.5}Sr_{0.5}MnO_{3} in a magnetic field up to 6T and for temperature down to 25K.We show that a gap (2\Delta_{CO} \approx 0.5eV opens up in the density of state (DOS) at the Fermilevel (E_F) on charge ordering (T_{CO}=150K) which collapses in an applied magnetic field when the charge ordered state melts. There is a clear correspondence between the behavior of the resistivity and the gap formation and its collapse in an applied magnetic field. We conclude that a gap in the DOS at E_F is necessary for the stability of the charge ordered state.Comment: 4 pages REVTeX, 5 postscript figures included, submitted to Phys. Rev. Let

The effect of substrate induced strain on the charge-ordering transition in Nd_{0.5}Sr_{0.5}MnO_{3} thin films

We report the synthesis and characterization of Nd_{0.5}Sr_{0.5}MnO_{3} thin films grown by the Pulsed Laser Deposition technique on 100 -oriented LaAlO_{3} substrates. X-ray diffraction (XRD) studies show that the films are 101 -oriented, with a strained and quasi-relaxed component, the latter increasing with film thickness. We observe that transport properties are strongly dependent on the thickness of the films. Variable temperature XRD down to 100 K suggests that this is caused by substrate induced strain on the films.Comment: 3 pages REVTeX, 4 figures included, submitted to AP