Strain-induced robust magnetic anisotropy and room temperature magnetoelectric coupling effect in epitaxial SmFeO 3 film
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Published online 14 August 2020 | https://doi.org/10.1007/s40843-020-1391-3
Strain-induced robust magnetic anisotropy and room temperature magnetoelectric coupling effect in epitaxial SmFeO3 film 1,2,3†
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Jun Zhang , Wuhong Xue , Tiancong Su , Huihui Ji , Zhi Yan , Guowei Zhou , 1,3 1,3* Zhiyong Quan and Xiaohong Xu ABSTRACT Rare-earth orthoferrite SmFeO3 is an outstanding single-phase multiferroic material, holding great potential in novel low-power electronic devices. Nevertheless, simultaneous magnetic and ferroelectric orders as well as magnetoelectric (ME) coupling effect at room temperature (RT) in this system have not been demonstrated yet. In this study, epitaxial SmFeO3 films were successfully prepared onto tensile-strain Nb-SrTiO3 (Nb-STO) substrates by a pulsed laser deposition (PLD) method. Measurement results show that the films exhibit obvious ferromagnetic and ferroelectric orders at RT. Meanwhile, the magnetic anisotropy gradually changes from out-of-plane (OP) to in-plane (IP) direction with increasing film thickness, which is attributed to the variations of O 2p-Fe 3d hybridization intensity and Fe 3dorbit occupancy caused by the strain-relaxed effect. Moreover, electrically driven reversible magnetic switching further proves that the SmFeO3 films exhibit the RT ME coupling effect, suggesting promising applications in new-generation electric-write magnetic-read data storage devices. Keywords: SmFeO3 film, multiferroicity, magnetoelectric coupling, magnetic anisotropy
INTRODUCTION Single-phase multiferroics, presenting the coexistence of ferroelectric and magnetic orders simultaneously, have been considered as one class of the most promising materials because of their vast application potential in spintronic devices, information storage, sensors, etc. [1–
6]. However, traditional theory holds that the two orders have incompatible occupation rules and thus lead to extremely rare multiferroic materials in nature [7]. Recently, spin-induced improper ferroelectricity has been widely explored in some oxide materials [8–11]. In such systems, the ferroelectric and magnetic orders bind each other and may exhibit strong magnetoelectric (ME) coupling effect. In order to explain the origin of the magnetically induced ferroelectricity, a large number of theoretical models were proposed one after another, such as reverse Dzyaloshinskii-Moriya (D-M) interaction [12], spin-dependent p-d hybridization and exchange striction mechanism [13,14]. So far, numerous single-phase multiferroic materials have been found, such as (Y, Sr, Gd, Dy, Tb, Ho, Lu)MnO3 films [15–18], (Dy, Gd, Tb, Ho, Er, Lu)CrO3 films [19–23], (Gd, Dy, Yb)FeO3 films [24–26], EuTiO3 films [27], hexaferrite Ba2−xSrxMg2Fe12O22 single crystal [28], and LaFeO3 polycrystal [29]. Despite rich characteristics and fascinating physics, the low working temperature and weak saturation magnetization (Ms) restrict the practical applications of these materials. In addition, some nanocomposite single-phase systems were also studied. For
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