The effect of in situ oxygen and vacuum annealings on the low bandwidth manganite Gd_1−x Ca _x MnO₃ (GCMO) thin film with x = 0.4 was investigated. Based on the magnetic measurements, the AFM–FM coupling is suppressed by the vacuum annealing treatment via destroying the double exchange interaction and increasing the unit cell volume by converting the Mn⁴⁺ to the Mn³⁺. Consequently, resistance increases significantly compared to pristine film. The results are explained by a model obtained from the positron annihilation studies, where the vacuum annealing increased the annihilation lifetime in A and B sites due to the formation of vacancy complexes V _A,B–V _O, which was not the case in the pristine sample. The positron annihilation analysis indicated that most of the open volume defects have been detected in the interface region rather than on the subsurface layer and this result is confirmed by detailed x-ray reflection analysis. On the other hand, the effect of oxygen annealing on the unit cell volume and magnetization was insignificant. This is in agreement with positron annihilation results which demonstrated that the introduction of oxygen does not change the number of cation vacancies significantly. This work demonstrates that the modification of oxygen vacancies and vacancy complexes can tune magnetic and electronic structure of the epitaxial thin films to provide new functionalities in future applications.

研究了原位氧气和真空退火对x = 0.4的低带宽锰酸盐Gd _{1- x} Ca _x MnO ₃ (GCMO) 薄膜的影响。基于磁性测量，真空退火处理通过破坏双交换相互作用和通过将 Mn ⁴⁺转化为 Mn ³⁺来增加晶胞体积来抑制 AFM-FM 耦合。因此，与原始薄膜相比，电阻显着增加。结果由从正电子湮没研究中获得的模型解释，其中真空退火由于空位复合物的形成而增加了 A 和 B 位点的湮灭寿命 V _A,B – V _O，在原始样品中并非如此。正电子湮灭分析表明，大多数开放体积缺陷是在界面区域而不是在地下层检测到的，这一结果通过详细的 X 射线反射分析得到证实。另一方面，氧退火对晶胞体积和磁化强度的影响微不足道。这与正电子湮灭结果一致，正电子湮灭结果表明氧的引入不会显着改变阳离子空位的数量。这项工作表明，氧空位和空位复合物的修饰可以调整外延薄膜的磁性和电子结构，为未来的应用提供新的功能。