Substrate effects on magnetic properties of LSMO thin films.

Temperature and magnetic field dependence of magnetization in LSMO films of 7.6 and 13.2 nm thicknesses grown on SrTiO₃ (100) and LaAlO₃ (100) substrates, respectively, were investigated by vibrating sample magnetometer. Coercive field (H_C), exchange bias (H_ε), and saturation magnetization (M_S) were measured from zero-field-cooled hysteresis loops at 5 K. H_C and H_ε are determined at 5 K using the relation, H_C = (H_C1 + H_C2)/2 and H_ε = (H_C1 - H_C2)/2, where H_C2 and H_C2 are the two magnetic fields where magnetization changes sign in hysteresis loops. Results show that M_S values are 476, 210 emu/cm³ and Hc values are 142, 655 Oe for LSMO film grown on SrTiO₃ and LaAlO₃ respectively. The sample grown on LaAlO₃ has H_ε ∼ -98 Oe which suggests the possible presence of both ferromagnetic and antiferromagnetic phases while the LSMO film on SrTiO₃ does not have an exchange bias. Further studies on understanding the effect of the substrate on magnetic properties of LSMO are in process.