Nd-Fe-B/FeCo多层纳米复合膜的结构和磁性

制备了Nd₂₈Fe₆₆B₆/Fe₅₀Co₅₀多层纳米复合磁性薄膜，对溅射态和650℃退火处理15 min试样的相成分分析和微结构的观察显示，溅射态薄膜呈非晶态，经650℃退火处理15 min后，薄膜主要相成分为硬磁性Nd₂Fe₁₄B相和软磁性相FeCo(110)相.Nd₂Fe₁₄B相呈柱状，其易磁化c轴垂直于膜面，尺寸约10 nm.在硬磁性相和软磁性相之间存在少量富Nd相和非晶态，富Nd相大小约7 nm.磁性测量和分析表明，1)该系列薄膜退火态具有垂直于膜面的磁晶各向异性.2)对于固定厚度(10 nm)层Nd-Fe-B和不同厚度(t_FeCo=1—100 nm)层FeCo多层纳米复合膜,剩磁随软磁相FeCo 厚度的增加快速增加，而矫顽力则减小.当t_FeCo=5 nm时，最大磁能积达到200 kJ/m³. 3)硬磁相Nd-Fe-B层和软磁相FeCo层之间交换耦合导致剩磁和磁能积增强. 关键词： Nd-Fe-B/FeCo多层纳米复合膜 交换耦合 磁各向异性

Nanostructure and hard magnetic properties of exchange coupled Nd-Fe-B/FeCo multilayer films

The nanocomposite Nd-Fe-B/FeCo mutilayer films have been prepared by rf sputtering. XRD results and HRTEM observation showed that as-deposited films deposited at substrate temperature of 300K were amorphous. The columnar grains of Nd₂Fe₁₄B phase with the c-axis perpendicular to the film plane developed after annealing at 923 K for 15 min. Nd₂Fe₁₄B grain size was about 10 nm in average and Nd-O particles of about 7 nm were dispersed within the grains and along the grain boundaries. The magnetization of these samples is found to increase with increasing FeCo layer thickness (t_FeCo) and the coercivity decreases with increasing t_FeCo. The multilayer films of maximum energy product is 200 kJ/m³ for t_FeCo=5 nm at room temperature. The enhancement of the remanence and energy product in nanocomposite films is attributed to the exchange coupling between the magnetically hard and soft phases.