Evolution of microstructure and magnetic properties in Co-Pt alloys bracketing the eutectoid composition
Evolution of microstructure and magnetic properties in Co-Pt alloys bracketing the eutectoid composition
复制标题
共析成分的 Co-Pt 合金显微组织和磁性能的演变
DOI：
10.1016/j.jmmm.2014.09.054
复制
发表时间：
2015
影响因子：
2.7
通讯作者：
J. Floro
中科院分区：
文献类型：
--
作者：
Priya Ghatwai;E. Vetter;M. Hrdy;W. Soffa;J. Floro
这项工作将具有Al-→L10+L12共析成分的Co-PT合金时效时的磁性能的演变与微观组织相关联。Co41.7Pt58.3的磁性随退火时间和温度的变化而变化，与微结构长度、相分数和有序度的变化相对应。这种合金的最大矫直力为4kOe，最大剩磁比为0.8，当应变的L10纳米粒子嵌入到A1基质中时，该合金在相变的早期阶段就出现了。当颗粒尺寸小于40 nm时，观察到较强的交换耦合。虽然L10纳米粒子严格低于零场作用下的单磁区临界尺寸，但我们认为，磁区壁钉扎的形式控制了峰值矫顽力样品中的磁化反转。在完全消耗A1相的长期时效后，X射线定量分析表明也存在L12相，这表明两相区域比预期的要宽。成分为Co37.6Pt62.4的样品时效后只形成软铁磁性L12。
This work correlates the evolution of magnetic properties with microstructure for aging of Co–Pt alloys with compositions bracketing the A1→L10+L12eutectoid at about 60 at% Pt. The magnetic properties of Co41.7Pt58.3were observed to vary intricately with annealing time and temperature, corresponding to changes in microstructural lengthscales, phase fractions, and degree of ordering. This alloy exhibited a maximum coercivity of 4 kOe and a maximum remanence ratio of 0.8, occurring at an early stage of transformation when strained L10nanoparticles are embedded in the A1 matrix. For particle sizes below 40 nm, robust exchange coupling is observed. Although the L10nanoparticles are rigorously below the single-domain critical size for zero applied field, we argue that a form of domain wall pinning controls magnetization reversal in the peak coercivity sample. After extended aging that completely consumes the A1 phase, quantitative x-ray analysis indicates that the L12phase is also present, suggesting that two-phase region is broader than expected. Samples with composition Co37.6Pt62.4formed only soft ferromagnetic L12upon aging.