Chanda Amit, DeTellem Derick, Hai Pham Yen Thi, Shoup Jenae E, Duong Anh Tuan, Das Raja, Cho Sunglae, Voronine Dmitri V, Trinh M Tuan, Arena Dario A, Witanachchi Sarath, Srikanth Hariharan, Phan Manh-Huong
Department of Physics, University of South Florida, Tampa, Florida 33620, United States.
Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 12116, Viet Nam.
ACS Appl Mater Interfaces. 2022 Mar 23;14(11):13468-13479. doi: 10.1021/acsami.1c23284. Epub 2022 Mar 8.
Understanding the effects of phase transition, phase coexistence, and surface magnetism on the longitudinal spin Seebeck effect (LSSE) in a magnetic system is essential to manipulate the spin to charge current conversion efficiency for spincaloritronic applications. We aim to elucidate these effects by performing a comprehensive study of the temperature dependence of the LSSE in biphase iron oxide (BPIO = α-FeO + FeO) thin films grown on Si (100) and AlO (111) substrates. A combination of a temperature-dependent anomalous Nernst effect (ANE) and electrical resistivity measurements show that the contribution of the ANE from the BPIO layer is negligible in comparison to the intrinsic LSSE in the Si/BPIO/Pt heterostructure, even at room temperature. Below the Verwey transition of the FeO phase, the total signal across BPIO/Pt is dominated by the LSSE. Noticeable changes in the intrinsic LSSE signal for both Si/BPIO/Pt and AlO/BPIO/Pt heterostructures around the Verwey transition of the FeO phase and the antiferromagnetic (AFM) Morin transition of the α-FeO phase are observed. The LSSE signal for Si/BPIO/Pt is found to be almost 2 times greater than that for AlO/BPIO/Pt; however, an opposite trend is observed for the saturation magnetization. Magnetic force microscopy reveals the higher density of surface magnetic moments of the Si/BPIO film in comparison to the AlO/BPIO film, which underscores the dominant role of interfacial magnetism on the LSSE signal and thereby explains the larger LSSE for Si/BPIO/Pt.
了解磁系统中相变、相共存和表面磁性对纵向自旋塞贝克效应（LSSE）的影响对于操纵自旋到电荷电流转换效率以用于自旋热电子学应用至关重要。我们旨在通过对生长在Si（100）和AlO（111）衬底上的双相氧化铁（BPIO = α-FeO + FeO）薄膜中LSSE的温度依赖性进行全面研究来阐明这些影响。温度相关的反常能斯特效应（ANE）和电阻率测量结果表明，即使在室温下，与Si/BPIO/Pt异质结构中的固有LSSE相比，BPIO层的ANE贡献也可以忽略不计。在FeO相的韦尔韦转变温度以下，BPIO/Pt上的总信号由LSSE主导。在FeO相的韦尔韦转变和α-FeO相的反铁磁（AFM）莫林转变附近，观察到Si/BPIO/Pt和AlO/BPIO/Pt异质结构的固有LSSE信号有明显变化。发现Si/BPIO/Pt的LSSE信号几乎是AlO/BPIO/Pt的2倍；然而，饱和磁化强度呈现相反的趋势。磁力显微镜显示，与AlO/BPIO薄膜相比，Si/BPIO薄膜的表面磁矩密度更高，这突出了界面磁性对LSSE信号的主导作用，从而解释了Si/BPIO/Pt具有更大的LSSE。
