FERROMAGNETIC-RESONANCE IN A SYSTEM COMPOSED OF A FERROMAGNETIC SUBSTRATE AND AN EXCHANGE-COUPLED THIN FERROMAGNETIC OVERLAYER
FERROMAGNETIC-RESONANCE IN A SYSTEM COMPOSED OF A FERROMAGNETIC SUBSTRATE AND AN EXCHANGE-COUPLED THIN FERROMAGNETIC OVERLAYER
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DOI：
10.1103/physrevb.34.7788
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发表时间：
1986-12-01
影响因子：
3.7
通讯作者：
ARROTT, AS
中科院分区：
文献类型：
--
作者：
COCHRAN, JF;HEINRICH, B;ARROTT, AS
本文利用Rado和Ament的理论以及Rado和Weertman的一般交换边界条件，讨论了由薄铁磁层交换耦合到厚铁磁衬底的复合系统对微波辐射的吸收与磁场的关系。假设覆盖层和基底通过形式为E ex=-J M A B的表面交换相互作用相互作用。在弱耦合强度到中等耦合强度的限制下，覆盖层铁磁共振（FMR）被JM B/d形式的有效场移位，其中M B是衬底平衡磁化强度，d是覆盖层厚度。当耦合参数J使得覆盖层和衬底FMR发生在几乎相同的外加磁场值时，对衬底吸收的磁场强度和位置的显著影响发生：微波吸收呈现出具有可比强度的两个峰。在非常强的耦合（J = 10 - 4 cm）的极限下，覆盖层和衬底中的磁化一起进动，产生一个吸收峰，其场值从对应于非钉扎表面的隔离衬底FMR的场值偏移。峰位置的偏移以及线宽的变化是由于覆盖层的存在而引起的有效表面钉扎引起的。这种钉扎可以通过有效表面能来描述，该有效表面能包含来自自由表面处的表面钉扎能的贡献加上与覆盖层厚度成比例的贡献，并且该贡献取决于磁化强度的差异和衬底与覆盖层材料之间的体积磁晶各向异性场的差异。
The theory of Rado and Ament and the general exchange boundary conditions of Rado and Weertman have been used to discuss the magnetic field dependence of the absorption of microwave radiation by a composite system consisting of a thin ferromagnetic overlayer exchange coupled to a thick ferromagnetic substrate. The overlayer and substrate are assumed to interact through a surface exchange interaction of the form E ex=− J M A⋅ M B. In the limit of weak to moderate coupling strengths, the overlayer ferromagnetic resonance (FMR) is shifted by an effective field of the form JM B/d, where M B is the substrate equilibrium magnetization and d is the overlayer thickness. Pronounced effects on the strength and position in magnetic field of the substrate absorption occur when the coupling parameter J is such that the overlayer and substrate FMR’s occur at nearly the same value of applied magnetic field: The microwave absorption exhibits two peaks having comparable strengths. In the limit of very strong coupling (J∼ 10− 4 cm) the magnetizations in the overlayer and in the substrate precess together to yield one absorption peak at a field value which is shifted from that corresponding to the isolated substrate FMR for an unpinned surface. The shift in peak position, as well as changes in the linewidth, is caused by an effective surface pinning due to the presence of the overlayer. This pinning can be described by an effective surface energy which contains contributions from the surface pinning energy at the free surface plus contributions which are proportional to the overlayer thickness and which depend on the difference in magnetization and on the difference in volume magnetocrystalline anisotropy fields between the substrate and overlayer materials.