La0.7Ca0.3MnO3 thin films grown on SrTiO3 (100) substrates by off-axis sputtering technique exhibit a fully strained film when the thickness of films is thinner than 25 nm. Transport and magnetic properties of the films for the magnetic field applied parallel to the surface of the films were consistent and could be easily explained by the domain-rotation model. However, these properties were not consistent when the field applied perpendicular to the substrate. The critical field for which peak resistivity was observed in the magnetoresistance measurement, Hc′(⊥) ∼ 79,500 A m- 1, one order of magnitude higher than the coercive field, Hc(⊥) ∼ 7950 A m- 1. The peak width of the in-plane X-ray diffraction peak (200) of the films as measured by a five-axis X-ray diffractometer showed an exponential decrease to the thickness of films. This broadening cannot be explained by the strain effect alone. We found that nanostructures, such as the ferromagnetic phase segregation in the paramagnetic matrix or the columnar structure in films that introduced excess domain walls, could be responsible for the inconsistency between Hc′(⊥) and Hc(⊥).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry