Beijing National Laboratory for Condensed Matter Physics and State Key Laboratory of Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Nanoscale. 2018 Dec 20;11(1):246-257. doi: 10.1039/c8nr06449k.
The tunable, nonvolatile electrical modulation of magnetization at room temperature is firstly demonstrated in a magnetically hard amorphous SmCo film grown on a (011)-cut 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) substrate. Uniaxial in-plane anisotropy with hard and easy axes lying in the [100] and [01-1] directions, respectively, occurs. Bipolar electric field, E, across the thickness direction enhances the remnant magnetization, Mr, along the hard axis, while suppresses the Mr along the easy axis, and the maximal regulation is about -5.8% and +2.2%, respectively. Detailed analysis indicates that the induced effective uniaxial magnetic anisotropy field, which arises from the magnetostrictive properties of the amorphous SmCo thin film and the anisotropic strain from the PMN-PT substrate, is mainly responsible for the anisotropic tunability. The variation of the directional pair ordering of the SmCo film, which is caused by the anisotropic strain due to the electric field, also contributes to the tunability. More importantly, nonvolatile modulation and a stable two-state memory effect are demonstrated for the bipolar case, and in situ X-ray diffraction and X-ray diffraction reciprocal space mapping reveal that these phenomena originate from the electric-field-induced rhombohedral-orthorhombic phase transformation in the PMN-PT substrate. Moreover, by unipolarizing the ferroelectric substrate, a nonvolatile modulation is also observed. The anisotropic nonvolatile control of magnetization in SmCo amorphous films opens a new avenue for developing multifunctional information storage and novel spintronics devices based on hard magnetic materials.
在（011）取向的 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3（PMN-PT）基片上生长的磁硬非晶 SmCo 薄膜中，首次演示了在室温下可调谐、非易失性的磁各向异性的电调制。该薄膜具有单轴各向异性，易轴和难轴分别沿[100]和[01-1]方向，外加双轴电场 E 可以增强难轴方向的剩余磁化强度 Mr，同时抑制易轴方向的 Mr，最大调节幅度分别约为-5.8%和+2.2%。详细分析表明，诱导各向异性的有效单轴磁各向异性场主要来源于非晶 SmCo 薄膜的磁致伸缩特性和 PMN-PT 基片的各向异性应变，这是非易失性可调谐的主要原因。由电场引起的各向异性应变导致 SmCo 薄膜的定向对有序性发生变化，这也有助于可调谐性。更重要的是，双极情况下可以实现非易失性调制和稳定的双态存储效应，原位 X 射线衍射和 X 射线衍射倒易空间映射表明，这些现象源于 PMN-PT 基片中的电场诱导三方-正交相转变。此外，通过单极化铁电基片，也可以观察到非易失性调制。SmCo 非晶薄膜的各向异性非易失性磁控为基于硬磁材料的多功能信息存储和新型自旋电子器件开辟了新途径。
