Barium strontium titanate (Ba 0.8 Sr 0.2 TiO 3 , BST) nanocrystalline ceramics have been synthesized by high energy ball milling. As the sintering temperature increases from 1200 ℃ to 1350 ℃, the average grain size of BST ceramics increases from 86 nm to 123 nm. The X-ray diffraction (XRD) studies show that these ceramics are tetragonal. The phase and grain size of the sintered pellets have been estimated from the XRD patterns, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The effect of grain size on dielectric and ferroelectric properties is studied. The dielectric and piezoelectric parameters are greatly improved at room temperature with increase in grain size. The Curie transition temperature is found to shift slightly towards higher temperatures as the grain increases from 86 nm to 123 nm. The coercive field decreases and the remnant polarization and spontaneous polarization increase as the grain size of BST nano ceramics increases. These ceramics are promising materials for tunable capacitor device applications.

In perpendicularly magnetized Pd/Co/Pd trilayers, the hydrogenation not only increased Kerr signal but also significantly enhanced the magnetic coercivity (HC) by 17%. The reversibility was demonstrated by cyclic H2 exposure. The time constants of hydrogen absorption and desorption effect on HC range from tens to hundreds seconds, depending on the H2 gas pressure. The magneto-optical Kerr signal and magnetic coercivity was simultaneously recorded during H2 absorption and desorption. These multifarious signals respond differently and provide a detailed understanding of hydrogenation effect on the functional Pd/Co/Pd trilayers.

Sizeable magnetic circular dichroism of artificially precipitated Co clusters in amorphous carbon AIP Advances 2, 032142 (2012) Ferromagnetic properties of GdN thin films studied by temperature dependent circular polarized spectroscopy Appl. Phys. Lett. 101, 072403 (2012) Carrier-dopant exchange interactions in Mn-doped PbS colloidal quantum dots Appl. Phys. Lett. 101, 062410 (2012) Faraday rotation effect in periodic graphene structureThe hydrogenation induced change of magneto-optical Kerr effect (MOKE) was studied in n ML Pd/30 ML Fe bilayers on Al 2 O 3 (0001). With the increasing of Pd thickness from 3 ML to 60 ML, the MOKE extinction angle was gradually shifted by 0.6 and the enhancement of Kerr intensity reached 35%-40% after exposure to 1 atm hydrogen. The reversibility of this significant change was demonstrated by cyclic desorption and reabsorption of hydrogen. This study reveals the sensitive MO response in the combination of a magnetic Fe thin film with a highly hydrogenated Pd capping layer. V C 2012 American Institute of Physics. [http://dx.

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