标题： 应变诱导的外延Ni-Mn-Ga薄膜马氏体相变及其与光学和磁光性质的相关性 显示英文标题

标题： Stress-induced Martensitic transformation in epitaxial Ni-Mn-Ga thin films and its correlation to optical and magneto-optical properties

摘要： 薄的外延Ni-Mn-Ga薄膜，厚度范围从8到160 nm，在0.7-6.4 eV的光谱范围内研究了其光学和磁光性质。 这些薄膜通过直流磁控溅射沉积在MgO基底上，基底上有应力中介的Cr缓冲层。 结构和磁性表征显示，厚度大于80 nm的薄膜发生了应力诱导的马氏体相变，而较薄的薄膜则保持由基底约束变形的奥氏体结构。 在马氏体样品中观察到了X型和Y型孪晶畴。 磁光法拉第效应光谱随着薄膜厚度的变化表现出显著的演化，展示了Ni-Mn-Ga的电子结构变化。 光谱椭偏仪和磁光法拉第光谱的结合使得能够推导出所研究样品的全介电张量的光谱依赖性。 三种磁光跃迁被拟合到非对角介电张量的光谱中，显示出与面内矫顽力的强相关性。 观察到的相关性突显了基底诱导应变对Ni-Mn-Ga薄膜的影响，并提供了与马氏体相变相关的电子结构变化的见解。 显示英文摘要

摘要： The optical and magneto-optical properties of thin epitaxial Ni-Mn-Ga films, with thicknesses ranging from 8 to 160 nm, were investigated across the spectral range of 0.7-6.4 eV. The films were deposited by DC magnetron sputtering on MgO substrate with stress-mediating Cr buffer layer. Structural and magnetic characterization revealed an stress-induced martensitic transformation for the films thicker than 80 nm, while thinner films remained in austenite structure deformed by substrate constraint. Both X-type and Y-type twin domains were observed in martensitic samples. Magneto-optical polar Kerr effect spectra showed notable evolution with film thicknesses, demonstrating changes in electronic structure of Ni-Mn-Ga. A combination of spectroscopic ellipsometry and magneto-optical Kerr spectroscopy allowed for the deduction of the spectral dependence of full permittivity tensor of investigated samples. Three magneto-optical transitions were fitted to the spectra of non-diagonal permittivity using semiclassical theory, showing strong correlations with in-plane coercivity. Observed correlations highlight the impact of substrate-induced strain on Ni-Mn-Ga films and provide insights into the electronic structure changes associated with the martensitic transformation.