Control of the magnetic properties of LaMnO$_{3}$ epitaxial thin films grown by Pulsed Laser Deposition

LaMnO$_{3}$ (LMO), the parent compound of colossal magnetoresistance based manganites has gained renewed attention as a building block in heterostructures with unexpected properties. In its bulk phase, stoichiometric LMO is an A-type antiferromagnetic (AFM) insulator (T$_{N}=$140K) with orthorhombic structure that easily accommodate an oxygen excess by generating cationic (La or Mn) vacancies. As a result, a fraction of Mn $^{3+}$ changes to Mn $^{4+}$ leading to a double-exchange mediated ferromagnetic (FM) behavior. In thin films the AFM phase has been elusive up to now and thin films with FM ordering are usually reported. In this work, we have systematically studied the growth process of LaMnO$_{3}$ thin films by pulsed laser deposition on SrTiO$_{3}$ (001) substrates under different oxygen partial pressures (PO$_{2})$. A close correlation between the structure (explored by XRD) and the magnetic properties (SQUID measurements) of the films with PO$_{2}$ has been identified. At high PO$_{2}$ FM behavior is observed. In contrast, at very low PO$_{2}$, the results obtained for unit cell volume (close to stoichiometric bulk values) and magnetic moment (0.2 $\mu_{B}$/Mn) strongly indicate antiferromagnetic ordering.