Synthesis and characterization of YBa2Cu3Ox thin films incorporating length-controlled nanorods
MELE Paolo, 松本 要, 本田 泰崇, 田中 敢 （九工大）； 一瀬 中 （電中研）； 吉田 隆, 一野 祐亮 （名大）； 向田 昌志 （九大）； 喜多 隆介 （静岡大）
Abstract:Jｃ of one-dimensional artificial pinning centers （APCs） such as BaZrO3， BaSnO3， Ba（Y0.5，Nb0.5）O3 nanorods decreases significantly when the magnetic field is inclined from the c-axis of the epitaxial YBCO films; in contrast， Jｃ of three-dimensional APCs such as Y2O3 nanoparticles is hardly changed. These behaviors depend on the different mechanism of vortex depinning from APCs. In the case of nanorods， a staircase state of the vortex line comes to stabilize in energy as the direction of the magnetic field is tilted from the direction of nanorod; however， the angular dependence of the pinning energy of nanoparticle is more gradual than that of nanorod. Nanorods can be changed into nanoparticles by controlling the nanorod length （8 nm – 120 nm in the present experiment）. The average distance among nanorods can be also easily tuned by changing the amount of the BaZrO3 or BaSnO3 addition. The broad peak of Jｃ in the c-axis direction on the angular dependence of Jｃ becomes small gradually as the length of the nanorod shortens. Simultaneously， the critical exponents at the vortex liquid-solid transition change from the Bose glass to the vortex glass. The relation between the dimension and the pinning mechanism of APCs will be discussed at the conference.