反应磁控溅射氧化镍薄膜的自旋塞贝克效应

自旋塞贝克效应是由(亚)铁磁体中的温度梯度引起自旋塞贝克电压信号的现象,目前已成为热自旋电子学研究的热点领域之一。本文采用反应磁控溅射工艺在Si衬底上沉积NiO薄膜,分别研究了溅射功率、氧氩比例、溅射气压、衬底温度对NiO薄膜微观结构和表面形貌的影响,实验中反应磁控溅射最适工艺条件为溅射功率110 W、氧氩比例0.15(O₂ 15 mL/min; Ar 100 mL/min)、溅射气压0.3 Pa、衬底温度400 ℃。研究了Si/NiO/Pt结构中温度梯度(温差)、磁场角度、NiO厚度变化和Pt厚度变化对自旋塞贝克电压的影响。结果表明,自旋塞贝克电压与温差呈简单的线性关系,温差越大测得的自旋塞贝克电压越高;磁场角度与自旋塞贝克电压之间满足余弦函数关系式,即在0°和180°时所得自旋塞贝克电压最大,90°和270°时为零;反铁磁性绝缘层NiO的厚度越大,所测得的自旋塞贝克电压信号越强;顺磁金属层Pt的厚度越大,自旋塞贝克电压信号越弱。

Spin Seebeck Effect of Nickel Oxide Thin Films Prepared by Reactive Magnetron Sputtering

The spin Seebeck effect is a phenomenon of spin Seebeck voltage signal caused by temperature gradient in (sub) ferromagnet, which has become one of the hot research fields of thermal spintronics. In this paper, NiO thin films were deposited on Si substrates by reactive magnetron sputtering. The effects of sputtering power, oxygen-argon ratio, sputtering pressure and substrate temperature on the microstructure and surface morphology of NiO thin films were investigated. The optimum conditions of reactive magnetron sputtering are sputtering power 110 W, oxygen-argon ratio 0.15 (O₂ 15 mL/min; Ar 100 mL/min), sputtering pressure 0.3 Pa and substrate temperature 400 ℃. The effects of temperature gradient (temperature difference), magnetic field angle, NiO thickness and Pt thickness on spin Seebeck voltage in Si/NiO/Pt structure were studied. The results show that there is a simple linear relationship between the spin Seebeck voltage and the temperature difference, the larger of the temperature difference, the higher of the spin Seebeck voltage, and the relationship between the magnetic field angle and the spin Seebeck voltage satisfies the cosine function, that is, the spin Seebeck voltage is the maximum at 0° and 180°, and zero at 90° and 270°. The greater of the thickness of the antiferromagnetic insulating layer NiO, the stronger of the measured spin Seebeck voltage signal. The thicker of the paramagnetic metal layer Pt, the weaker of the spin Seebeck voltage signal.