Electric field-modified segregation in crystal fibers of colossal magnetoresistive La0.7Ca0.3MnO3

Manganites are materials with a high potential for applications in magnetic sensors, head-reading magnetoresistives hard disk, RAM memories and actuator devices, among others. Laser heated floating zone (LHFZ) growth of manganite fibers is a suitable technique to obtain high-quality crystals. In this study, an electric field was simultaneously applied to LHFZ in order to control the solidification morphology. Manganite fibers of La0.7Ca0.3MnO3 composition were grown under an applied DC electric current density in the range 0−15.2 A/cm2. At 11.4 A/cm2 the solid/liquid (S/L) interface morphology changes from planar to cellular. The electric field promotes constitutional supercooling conditions by field-freezing the system, and the Ca effective segregation coefficient increasing from k=0.60 towards the unity. At the same time, when the current density increases from 11.4 to 15.2A/cm2, the intercellular spacing reduces from 22 to 11 μm.