Intrinsic and extrinsic pressure effects in La0.7Ca0.3MnO3 thin films

The influence of quasihydrostatic pressure on the electrical transport in e pitaxial La0.7Ca0.3MnO3/MgO(100) thin films prepared by pulsed laser deposi tion (PLD) and metalorganic aerosol deposition (MAD) was studied for temper atures T=4.2-300 K and magnetic fields B=0-12 T. Usual or "intrinsic" press ure effect, characterized by a decrease of the resistance in the region of the metal-insulator transition T-MI was observed in PLD film for p=0-16 kba r and also in MAD films for p less than or equal to 8 kbar. An anomalous, o r "extrinsic" pressure effect, characterized by a 2-3 order of magnitude in crease of the resistance at low temperatures, persisting after the pressure release, was found for p > 8 kbar in films with extraordinarily high value s of the pressure coefficient d(T-MI)/dp=2.70-3.85 K/kbar. The lattice stra in originated from the substrate due to epitaxy was found to control the T- MI values and intrinsic pressure behavior in the films. The extrinsic press ure effect in MAD films is caused by a plastic deformation of the film, yie lding irreversible changes of the microstructure accompanied by a magnetore sistance, Delta R(B)/R(B), more than 10(3)% at 4.2 K < T < T-MI. (C) 2000 A merican Institute of Physics. [S0021-8979(00)05221-X].