The ferromagnetic phase of ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnO}}_3$ thin films has been investigated through measurements of magnetization loops at different temperatures, zero-field-cooled and field-cooled magnetization curves obtained under different magnetic fields. We have found that the main sources of the “bulk” coercivity in manganite films are the film/substrate interface and film surface. The temperature dependence of the coercivity is described by a “strong domain-wall pinning” model, independently of the thickness and substrate. The magnetization-vs-temperature curves, measured under different magnetic fields $(10\mathrm{}\hspace{0.5em}\mathrm{Oe}<H<\mathrm{}2.5\mathrm{}\hspace{0.5em}\mathrm{kOe}),$ have been explained in terms of the magnetic hysteresis of the films. We find no evidence of glass states or of the existence of single-domain clusters, as suggested by other authors.

• Received 8 July 2001

DOI:https://doi.org/10.1103/PhysRevB.65.094431