Apostolov Angel T, Apostolova Iliana N, Wesselinowa Julia Mihailowa
University of Architecture, Civil Engineering and Geodesy, 1046 Sofia, Bulgaria.
University of Forestry, 1756 Sofia, Bulgaria.
Materials (Basel). 2024 Apr 25;17(9):1995. doi: 10.3390/ma17091995.
The film thickness, temperature, substrate and doping dependence of the phonon energy ω and damping γ, as well as the electrical conductivity, of pure and Sr-doped LaMnO thin films near the phase transition temperature TN are investigated using a microscopic model and the Green's function technique. Due to the strong spin-phonon interaction, there appears a kink at TN in the temperature dependence of ω(T) and γ(T). The softening and hardening of the ω = 495 cm (A) and ω = 614 cm (B) modes is explained by the different sign of the anharmonic spin-phonon interaction constant . The damping increases with for both cases because it is proportional to R2. ω decreases whereas γ increases with an increasing Sr concentration. This is due to the strain caused by the difference between the ionic radii of the La and Sr ions. The film thickness dependence is also considered. ω and γ increase strongly with the decreasing film thickness. The electrical conductivity is enhanced after the doping of the LMO thin films with Sr, which could be used for energy storage applications. The observed results are in good qualitative agreement with the experimental data.
利用微观模型和格林函数技术，研究了纯LaMnO薄膜和掺Sr的LaMnO薄膜在相变温度TN附近的薄膜厚度、温度、衬底以及掺杂对声子能量ω和阻尼γ的影响，以及电导率的影响。由于强烈的自旋-声子相互作用，ω(T)和γ(T)的温度依赖性在TN处出现一个扭折。ω = 495 cm（A）和ω = 614 cm（B）模式的软化和硬化是由非谐自旋-声子相互作用常数的不同符号来解释的。两种情况下阻尼都随 增加，因为它与R2成正比。随着Sr浓度的增加，ω减小而γ增加。这是由于La和Sr离子的离子半径差异引起的应变。还考虑了薄膜厚度依赖性。ω和γ随薄膜厚度的减小而强烈增加。用Sr掺杂LMO薄膜后电导率增强，这可用于能量存储应用。观察结果与实验数据在定性上吻合良好。
