在5%Nb掺杂的SrTiO3衬底上用磁控溅射法外延生长了La1/aCa7/aMnO3薄膜形成异质结,该异质结有类似于传统P-n结的整流特性.磁场下扩散电压减小,当温度低于130 K以下,扩散电压的减小非常明显.这和在此温度以下,La1/8Ca7/aMnO3出现自旋倾斜态密切相关.我们计算出异质结的结电阻和磁致电阻(MR),在不同大小的正负偏压,不同磁场下,都得到负的MR值.我们给出界面附近的La1/8Ca7/8MnO3的能带结构并分析了外加磁场对洪德耦合,Jahn-Teller畸变等机制的作用,来解释该异质结的磁输运行为.结果有助于了解高Ca掺杂锰氧化物异质结的性质.
A heterojunction composed of La1/8 Ca7/8 MnO3 and Nb-doped SrTiO3 was fabricated, which shows rectifying characteristic like conventional p-n junctions. The diffusion voltage is slightly decreased under magnetic fields at high temperature and the effect of magnetic fields is more obvious at temperatures below 130 K, at which spin canting state appears in La1/8Ca7/8MnO3. A negative magnetoresistance was found in this heavily Ca-doped manganite heterojunction due to the majority spin carriers (MASCs) transport at the manganite-titanate interface. An energy band structure employing both Jahn-Teller distortion and Hund's coupling of electrons at the interface is used to explain the MASCs' magneto-transport behaviors.
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