摘要
在加热到400℃的MgO(001)单晶基片上,用磁控溅射法沉积30 nm厚A1相FePt软磁薄膜,在T_a=[400℃,700℃]温度范围进行6 h热处理,使其发生不同程度的A1→L1_0转变.以此作为硬磁层,在100℃继续生长不同厚度的A1相FeP t,得到具有(001)织构的L1_0/A1-Fe Pt双层磁性交换弹簧.T_a≤600℃,硬磁层的覆盖率保持100%,但晶粒尺寸有差别.T_a=500℃和600℃,硬磁层的有序度分别为0.61和0.84,层中L1_0相与A1相共存,两相间的交换作用使薄膜出现垂直磁晶各向异性,磁化曲线呈方形.矫顽力在T_a=500℃时接近5 kOe.用T_a=500℃和600℃的硬磁层做成L1_0(001)/A1-Fe Pt双层薄膜,在软磁层厚度为20 nm时,磁化曲线仍然保持方形,而软磁层厚度增加到30 nm,反磁化曲线分成软磁层反转和硬磁层反转两个阶段,表明层间交换作用长度都在20 nm<lex<30 nm范围,是理想L1_0/A1-FePt交换弹性体系的2倍以上.经过分析认为,出现这种现象的原因在于硬磁层中L1_0相与A1相共存,降低了有效单轴磁晶各向异性能密度.这为根据需要设计磁性弹簧的性质提供了方便.
Soft A1-FePt （30 nm） films were magnetron-sputtered on MgO（001） single-crystal substrates at an elevated temperature of 400℃, and subsequently annealed at diffrent temperatures in range of Ta=[400℃, 700℃] for 6 h in order to turn them into hard magnets with different degrees of A1→L10 transformation. Then second layers of A1-FePt with different thicknesses were covered at 100℃ to obtain L10-FePt/A 1-FePt bilayer magnetic exchange springs with （001） textures. At Ta≤600℃, the coverage of hard layer was -100%, though the grain size increased with Ta. The surface roughness reduced from 2.45 to 1.02 nm if the film was annealed at Ta=500℃. The surface of hard layer flattened by annealing should benefit to improve the strength of interlayer exchange interaction. At Ta=500℃ and 600℃, Al-FePt and L10-FePt coexisted in the hard layer with an ordering degree of 0.61 and 0.84, respectively. The direction of magnetic easy axis began to switch from in plane to out of plane at Ta=500℃, indicating a vertical magnetocrystalline anisotropy was generated. The out-of-plane magnetization curves showed rectangle-like shapes at 500℃≤ T≤600℃, in spite of the soft phase left in hard layer, and a moderate coercive force of -5 kOe was obtained at Ta=500℃. This indicates the exchange interaction between coexistent two phases in hard layer was strong enough to pin the soft magnetic moments with the hard ones. At Ta=700℃, the coercive force exceeded 20 kOe, which is too huge to be affected by exchange springs. By using the film of Ta=500℃ as hard layer, LI0/A1-FePt bilayer film with 20 nm thick soft layer kept rigid behaviors with almost the same coercive force of single hard layer, and respective reversal steps for soft layer and hard layer appeared in the magnetization curve if the thickness of soft layer was 30 nm, with a reduced coercive force of -4 kOe. As double shoulders should appear in the hysteresis loop if the thickness of soft layer exceeds twice of domain wall thickness of hard laye
作者
魏娟
杜斌
李佳芹
姚雅芹
陈阳
李鱼辉
曾道富
李国庆
张昆华
闻明
WEI Juan DU Bin LI JiaQin YAO YaQin CHEN Yang LI YuHui ZENG DaoFu LI GuoQlng ZHANG KunHua WEN Ming(School of Physical Science and Technology, Southwest University, Chongqing 400715, China Kunming Institute of Precious Metals, Kunming 650106, China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2017年第15期1611-1619,共9页
Chinese Science Bulletin
基金
国家自然科学基金(51262015)
国家大学生创新创业训练计划(201510635044)资助
关键词
L10-FePt/A1-FePt双层薄膜
磁性弹簧
矫顽力
交换作用长度
Anisotropy
Annealing
Coercive force
Exchange interactions
Magnetic moments
Magnetism
Magnetization
Magnetization reversal
Magnetocrystalline anisotropy
Surface roughness
