Exchange bias associated with phase separation in the perovskite cobaltite La 1 − x Sr x CoO 3
Exchange bias associated with phase separation in the perovskite cobaltite La 1 − x Sr x CoO 3
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DOI：
10.1103/physrevb.73.174419
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发表时间：
2006-05
影响因子：
3.7
通讯作者：
Yan-kun Tang;Young Sun;Zhaohua Cheng
中科院分区：
文献类型：
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作者：
Yan-kun Tang;Young Sun;Zhaohua Cheng
采用一种新的方法合成了LiTi_2O_4多晶样品（T-c约为12.3K），测量了其电阻率和Andreev反射谱。在90 K以上，电阻率随温度的变化符合Bloch-Gruneisen理论。这与电子-声子散射的图像是一致的。低于90 K和高于T-c时，它显示出T-2温度依赖性，表明T-c以上的费米液体行为。根据Ginzburg-Landau理论，从H-c ~ 2-T相图中估算出上临界场H-c ~ 2（0）约为11.6T。点接触Andreev反射谱给出2 Delta（0）/k（B）T（C）近似为4，表明LiTi_2 O_4是一种典型的中间耦合s波BCS超导体。我们还观察到在正常状态下的电阻驼峰和在老化样品上的ρ（T）曲线的过渡区附近的场致上弯。通过与新化合物的比较，表明上述奇异的rho（T）行为不是纯化学计量比LiTi_2 O_4化合物的本征特征。
We measured resistivity and Andreev reflection spectroscopy on LiTi2O4 polycrystalline samples (T-c approximate to 12.3 K) synthesized by a new method. Resistivity shows the metallic temperature dependence and is well fitted by the Bloch-Gruneisen theory above 90 K. This is consistent with the picture of electron-phonon scattering. Below 90 K and above T-c it shows T-2 temperature dependence suggesting Fermi liquid behavior above T-c. From the H-c2-T phase diagram the upper critical field H-c2(0) is estimated to be about 11.6 T based on the Ginzburg-Landau theory. Point-contact Andreev reflection spectroscopy gives 2 Delta(0)/k(B)T(C)approximate to 4 and reveals that LiTi2O4 is a typical intermediate-coupling s-wave BCS superconductor. We also observed the resistive hump in a normal state and the field-induced upturn near the transition region of the rho(T) curve on the aged samples. In comparison with the fresh one, it suggests that the above exotic rho(T) behavior is not an intrinsic character of the pure stoichiometric LiTi2O4 compound.