Low temperature magnetic properties and Raman spectrum of highly (111)-oriented rhombohedral BiFeO3 (BFO) thin films epitaxially grown on (111) SrTiO3 substrates by pulsed laser deposition have been studied. Zero field cooled (ZFC) and field cooled (FC) magnetization curves display divergence at characteristic temperature Tirr (H), which are magnetic field dependent, suggesting a spin-glass like behavior of the film. The change in magnetic ordering results in anomalous phonon behavior such as the extraordinary enhancement and appearance of new Raman modes due to Brillouin zone folding below ∼200 K.

The effects of the growth conditions and the lattice strains of pulsed laser deposited (PLD) La0.7Sr0.3MnO3 (LSMO) thin films upon the magnetic behavior have been studied using magneto-optical Kerr effect (MOKE) at room temperature. First, the structural quality of the films was investigated by XRD and the surface morphology was studied using AFM. It is shown that both surface morphology and crystallinity are optimized when the target-to-substrate distance and the oxygen pressure are chosen in agreement with a PD3 scaling law. Secondly, hysteresis loops have been recorded along the [100], [110] and [001] directions and the easy directions of magnetization have been determined for both stress states, i.e. tension on SrTiO3 and compression on LaAlO3. In tensile films, the whole plane is found to be easy, whereas, in compressive films, the easy axis should be an intermediate direction between the film's plane and its normal. Moreover, tensile films deposited under optimized growth conditions exhibit the largest anisotropy coefficient (K1eff = -6.9×105 erg/cm3).

We report the growth and characterization of Nd0.5Sr0.5MnO3 thin films deposited by the Pulsed Laser Deposition (PLD) technique on [100]-oriented LaAlO3 substrates. X-ray diffraction (XRD) studies show that the films are [101]-oriented, with a strained and quasi-relaxed component, the latter increasing with film thickness. A post-annealing under oxygen leads to a quasi-relaxed film with a metallic behavior. We also observe that transport properties are strongly dependent on the thickness of the films. Variable temperature XRD down to 100 K suggests that this is caused by substrate-induced strain on the films.

We have synthesized ceramics of A2FeReO6 double-perovskites A2FeReO6 (A=Ba, Ca). Structural characterizations indicate a cubic structure with a=8.0854(1) Å for Ba2FeReO6 and a distorted monoclinic symmetry with a=5.396(1) Å, b=5.522(1) Å, c=7.688(2) Å and β=90.4° for Ca2FeReO6. The barium compound is metallic from 5K to 385K, i.e. no metal-insulator transition has been seen up to 385K, and the calcium compound is semiconducting from 5K to 385K. Magnetization measurements show a ferrimagnetic behavior for both materials, with Tc =315 K for Ba2FeReO6 and above 385K for Ca2FeReO6. At 5K we observed, only for Ba2FeReO6, a negative magnetoresistance of 10% in a magnetic field of 5T. Electrical, magnetic and thermal properties are discussed and compared to those of the analogous compounds Sr2Fe(Mo,Re)O6 recently studied.

L'étude microstructurale des films minces supraconducteurs de formule générale : ${\rm (CaCuO_2)}_m{\rm (Ba_2CuO_2CO_3)}_n$, déposés à partir d'une seule cible, a montré qu'ils sont formés de nombreuses intercroissances. Ceci les rend pratiquement inutilisables pour des caractérisations physiques fines. Dans cet article sont présentées les étapes de la mise en oeuvre du système multicible nécessaire à la croissance d'un empilement régulier.