Magnetoelastic coupling of La0.7Sr0.3MnO3 films near the structural phase transition in SrTiO3

La0.7Sr0.3MnO3 (LSMO) films were grown on vicinal (miscut angle 0.1 ) SrTiO3(100) substrates by pulsed laser deposition at an oxygen partial pressure of 200 mTorr and a substrate temperature of 600 C. XRD and TEM cross-sectional investigations showed heteroepitaxial growth with excellent structural quality of the LSMO layer. Three films with thickness of 40, 15 and 5 nm, respectively, were selected for further magnetic characterization by SQUID magnetometry and ac susceptometry. In agreement with the high structural quality the films were found to be magnetically very soft with coercive fields below 1 mT near 100 K. These low coercivities enabled a detailed study of the coupling between the magnetic properties of the LSMO films and structural distortions that occur below the structural transition in the SrTiO3 substrates. Below 105 K the development of a two-step transition in the magnetic response is clearly observed. This is discussed in terms of the formation of two different types of magnetic domains with different coercivities in the LSMO film as a response to twinning in the SrTiO3 substrate