Carreira Santiago J, Aguirre Myriam H, Briatico Javier, Steren Laura B
Consejo Nacional de Investigaciones Científicas y Técnicas Argentina
Laboratorio de Nanoestructuras Magnéticas y Dispositivos, Dpto. Materia Condensada, Instituto de Nanociencia y Nanotecnología (INN), Centro Atómico Constituyentes (CNEA) 1650 San Martín Buenos Aires Argentina.
RSC Adv. 2019 Nov 25;9(66):38604-38611. doi: 10.1039/c9ra06552k.
Strong correlated manganites are still under intense research owing to their complex phase diagrams in terms of Sr-doping and their sensitivity to intrinsic and extrinsic structural deformations. Here, we performed X-ray absorption spectroscopy measurements of manganite bilayers to explore the effects that a local Sr-doping gradient produce on the charge and antiferromagnetic anisotropies. In order to gradually tune the Sr-doping level along the axis perpendicular to the samples we have grown a series of bilayers with different thicknesses of low-doped manganites (from 0 nm to 6 nm) deposited over a LaSrMnO metallic layer. This strategy permitted us to resolve with high accuracy the thickness region where the charge and spin anisotropies vary and the critical thickness over which the out of plane orbital asymmetry does not have any further modifications. We found that the antiferromagnetic spin axis points preferentially out of the sample plane regardless the capping layer thickness. However, it tilts partially into the sample plane far from this critical thickness, owing to the combined contributions of the external structural strain and electron doping. Furthermore, we found that the doping level of the capping layer strongly affects the critical thickness, giving clear evidence of the influence exerted by the electron doping on the orbital and magnetic configurations. These anisotropic changes induce subtle modifications on the domain reorientation of LaSrMnO, as evidenced from the magnetic hysteresis cycles.
强关联锰氧化物因其在锶掺杂方面复杂的相图以及对本征和非本征结构变形的敏感性，仍处于深入研究之中。在此，我们对锰氧化物双层膜进行了X射线吸收光谱测量，以探究局部锶掺杂梯度对电荷和反铁磁各向异性产生的影响。为了沿垂直于样品的轴逐渐调节锶掺杂水平，我们生长了一系列双层膜，其中低掺杂锰氧化物（厚度从0纳米到6纳米）沉积在LaSrMnO金属层上。这种策略使我们能够高精度地分辨出电荷和自旋各向异性发生变化的厚度区域，以及平面外轨道不对称性不再有进一步变化的临界厚度。我们发现，无论覆盖层厚度如何，反铁磁自旋轴优先指向样品平面之外。然而，由于外部结构应变和电子掺杂的共同作用，在远离该临界厚度时，它会部分倾斜到样品平面内。此外，我们发现覆盖层的掺杂水平强烈影响临界厚度，这清楚地证明了电子掺杂对轨道和磁构型的影响。这些各向异性变化对LaSrMnO的畴重新取向产生了细微的改变，这从磁滞回线中可以得到证明。
