近日，课题组与合作者在无铅垂直取向纳米复合（VAN）薄膜的磁电耦合效应调控方面取得重要进展。研究团队通过引入铁电（FE）覆盖层封装策略，有效解决了传统VAN薄膜中因铁磁（FM）相暴露于铁电基体表面而导致的磁电耦合不充分问题。相关成果以“Enhanced magnetoelectric coupling invertically aligned nanocomposite thin films via ferroelectric capping layer encapsulation”为题发表于美国物理联合会期刊Applied Physics Letters(Appl. Phys. Lett. 128, 132904 (2026) )。

研究团队以NBT-CFO体系为模型，采用脉冲激光沉积在VAN薄膜表面沉积NBT铁电覆盖层。结果表明，覆盖层成功封装了暴露的CFO纳米柱，恢复了界面应变耦合完整性，表面粗糙度从11 nm降至3.1 nm。磁学测量显示，50 nm厚样品的垂直磁各向异性从3.08×10⁴ J/m³提高至9.49×10⁴ J/m³（增幅208%），矫顽场增加128%，且增强效应随厚度增加而减弱。磁电耦合性能方面，直接磁电（DME）系数从80提升至216 mV/(cm·Oe)（增幅170%），逆磁电（CME）系数从6.32×10⁻¹⁰提升至8.17×10⁻¹⁰ s/m（提升近30%），漏电流显著降低，工作电压窗口从±3 V扩展至±9 V。

该工作揭示的核心机制是：铁电覆盖层将暴露的铁磁相重新纳入应变网络，通过恢复界面磁弹耦合优化VAN薄膜性能。该策略具有普适性，可为高密度、低功耗磁电存储器件设计提供新思路。

Recently, our group, in collaboration with partners, has made progress in regulating the magnetoelectric coupling of lead-free vertically aligned nanocomposite (VAN) thin films. By introducing a ferroelectric (FE) capping layer encapsulation strategy, we addressed the issue of insufficient coupling caused by the exposure of ferromagnetic (FM) phases on the ferroelectric matrix surface. The related work is published in Applied Physics Letters under the title 'Enhanced magnetoelectric coupling invertically aligned nanocomposite thin films via ferroelectric capping layer encapsulation' (Appl. Phys. Lett. 128, 132904(2026)).

Using the NBT-CFO system as a model, we deposited an NBT FE capping layer on the VAN film surface via pulsed laser deposition. Results show that the capping layer successfully encapsulates the exposed CFO nanopillars, restoring interfacial strain coupling integrity, while the surface roughness decreases from 11 nm to 3.1 nm. Magnetic measurements reveal that for the 50 nm-thick sample, the perpendicular magnetic anisotropy increases from 3.08×10⁴ to 9.49×10⁴ J/m³ (an increase of 208%), and the coercive field increases by 128%; this enhancement weakens with increasing film thickness. Regarding magnetoelectric coupling performance, the direct magnetoelectric (DME) coefficient increases from 80 to 216 mV/(cm·Oe) (anincrease of 170%), and the converse magnetoelectric (CME) coefficient increases from 6.32×10⁻¹⁰ to 8.17×10⁻¹⁰ s/m (an increase of nearly 30%), while leakage current is significantly reduced and the operating voltage window expands from ±3 V to ±9 V.

This work reveals that the core mechanism is the reincorporation of exposed FM phases into the strain network via the FE capping layer, which optimizes VAN film performance by restoring interfacial magnetoelastic coupling. This universal strategy provides new insights for the design of high-density, low-power magnetoelectric memory devices.

图1 NBT覆盖层对NBT-CFO垂直取向纳米复合薄膜磁性的影响：(a)-(c)厚度分别为50、100和300 nm的NBT-CFO样品在NBT铁电覆盖层封盖前后，面外磁滞回线的对比；(d) NBT覆盖层引起的薄膜矫顽场变化幅度ΔHc%随薄膜厚度的演变；(e) NBT覆盖层封盖前，NBT相和CFO相的面外晶格应变状态示意图；(f) NBT覆盖层封盖后，NBT相和CFO相的面外晶格应变状态示意图。

论文第一作者为23级硕士研究生张晓暄。论文链接：https://pubs.aip.org/aip/apl/article/128/13/132904/3385876