1. Dislocations in Thin Films of Ferroic Oxides
Institute of Materials Science
Dislocations in Thin Films of Ferroic Oxides
S. Pamir Alpay
Materials Science and Engineering
University of Connecticut
There are built-in (internal) magnetic fields induced by a spatially varying magnetization in a compositionally graded ferromagnet.
Ferroic materials (ferroelectrics, ferromagnets, ferroelastics…) find many applications as sensors and actuators. To be used in microelectronics, they are deposited in thin film form ( nm thick). The defects (dislocations, vacancies) introduced during this process have to be controlled carefully as these will reduce ALL functional properties.
LaAlO3
16.7 nm
PbTiO3 15 z x
Polarization (C/m2)
Magnetization measured with the magnetic field applied along the grading direction in a compositionally graded hexa-ferriete with composition BaCoxTixFe12-2xO19 with x = 0, 0.4, 1.2, 1.4, and 1.6. Open symbols: Magnetization measured with the magnetic field applied perpendicular to the grading direction. These data were collected at T=300K. Inset: M(H) loops near H=0.
Theoretically calculated spatial variation of the polarization in a 15 nm thick PbtiO3 film on LaAlO3 substrate. Strong polarization variations in the whole volume of the film will result in extremely high electrostatic fields that may entirely suppress ferroelectricity in ultra-thin films such as the one for which this simulation was carried out.
Should dislocations or other defects such as vacancies form in ferromagnetic materials, a similar built-in field as in the case of graded samples can be expected.