Epitaxial La 2 NiMnO 6 thin films have been grown on (001)-orientated SrTiO 3 using the pulsed laser deposition technique. The thin films samples are semiconducting and ferromagnetic with a Curie temperature close to 270 K, a coercive field of 920 Oe, and a saturation magnetization of 5 µ B per formula unit. Transmission electron microscopy, conducted at room temperature, reveals a majority phase having "I-centered" structure with a ≈ c ≈ a sub 2 and b ≈ 2a sub along with minority phase domains having a "P-type" structure (a sub being the lattice parameter of the cubic perovskite structure). A discussion on the absence of Ni/Mn long-range ordering, in light of recent literature on the ordered double-perovskite La 2 NiMnO 6 is presented.

The outermost member of the 112 family LaBaCo 2 O 5.5 has been synthesized using a multistep method to stabilize its structure. Its structural study, combining neutron powder diffraction and electron microscopy, shows that its orthorhombic matrix consists of layers of corner-shared CoO 6 octahedra interconnected through CoO 5 pyramids like in the other 112 cobaltates but contains small LaBaMn 2 O 5.5 -type domains (8%) due to local oxygen displacement. Its magnetic properties and magnetic structure evidence the following features: G-type antiferromagnetic/G-type ferrimagnetic/paramagnetic with T N ) 260 K and T C ) 326 K. This cobaltate differs from other 112 cobaltates by its antiferromagnetic structure which keeps the same symmetry as its ferrimagnetic phase, probably due to the size effect of La 3+ upon crystal field. Trivalent cobalt is shown to keep the intermediate spin state in the whole temperature range from 10 to 326 K.

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Epitaxial CaMnO 3 films grown with 2.3% tensile strain on (001)-oriented LaAlO 3 substrates are found to be incipiently ferroelectric below 25 K. Optical second harmonic generation (SHG) was used for the detection of the incipient polarization. The SHG analysis reveals that CaMnO 3 crystallites with in-plane orientation of the orthorhombic b axis contribute to an electric polarization oriented along the orthorhombic a (respectively c) axis in agreement with the predictions from density functional calculations.

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We study the geometry of needle-shaped domains in shape-memory alloys. Needleshaped domains are ubiquitously found in martensites around macroscopic interfaces between regions which are laminated in different directions, or close to macroscopic austenite/twinned-martensite interfaces. Their geometry results from the interplay of the local nonconvexity of the effective energy density with long-range (linear) interactions mediated by the elastic strain field, and is up to now poorly understood. We present a two-dimensional shape optimization model based on finite elasticity and discuss its numerical solution. Our results indicate that the tapering profile of the needles can be understood within finite elasticity, but not with linearized elasticity. The resulting tapering and bending reproduce the main features of experimental observations on Ni 65 Al 35 .