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首页> 外文期刊>Physica, B. Condensed Matter >Evidence of superparamagnetic behaviour in an amorphous Ni62Mn38 film by ESR measurements
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Evidence of superparamagnetic behaviour in an amorphous Ni62Mn38 film by ESR measurements

机译：通过ESR测量在非晶态Ni62Mn38膜中超顺磁行为的证据

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Electron spin resonance (ESR) measurements were carried out on an amorphous Ni62Mn38 film in the temperature range of 4-300 It. The spectra comprise multi-peak resonance absorptions forming mainly two groups separated in the magnetic field; one of which corresponds to unresolved usual spin-wave resonance (SWR) modes, the other occurs at about H = 3 kG for the applied field parallel to the film surface and shows a rather less dependence on the field direction compared to those of the main SWR modes. It has been observed that the latter peak becomes more and more apparent (the amplitude intensifies and the linewidth decreases) with decreasing temperature and then starts again to broaden as the temperature is further decreased. This overall behaviour leads us to suggest that the sample consists of a large number of smaller clusters coupled weakly to each other. Macroscopic ferromagnetic state averaged over all these clusters gives us the usual SWR peaks. However, each weakly coupled cluster behaves as an almost free individual magnetic entity and therefore the latter peak can be attributed to the superparamagnetic resonance absorbtions. By fitting the theoretical SWR modes simultaneously to the corresponding experimental ones for parallel and perpendicular geometries, the exchange stiffness constant D, the exchange unidirectional anisotropy field H-exe, the bulk magnetic anisotropy constant 2K(eff)/M-0 and the surface pinning parameter QL have been obtained as a function of temperature. The results have been compared with the existing data for the NiMn alloys with different compositions. The role of the local spin fluctuations (LSFs) on the temperature dependence of the magnetic parameters mentioned above has been discussed. (C) 1998 Elsevier Science B.V, All rights reserved. [References: 27]
机译：在4-300 It的温度范围内对非晶态Ni62Mn38膜进行电子自旋共振（ESR）测量。频谱包括多峰共振吸收，主要形成两个在磁场中分离的基团。其中一个对应于未解决的通常的自旋波共振（SWR）模式，对于平行于薄膜表面的外加电场，另一个发生在大约H = 3 kG处，与主方向相比，对电场方向的依赖性较小SWR模式。已经观察到，随着温度的降低，后一个峰变得越来越明显（振幅增强，线宽减小），然后随着温度的进一步降低再次开始变宽。这种总体行为使我们建议样本由大量彼此弱耦合的较小簇组成。在所有这些簇上平均的宏观铁磁状态给出了通常的SWR峰。但是，每个弱耦合的簇表现为几乎自由的单个磁性实体，因此后一个峰可归因于超顺磁共振吸收。通过将理论SWR模式同时与相应的平行和垂直几何实验模式拟合，交换刚度常数D，交换单向各向异性场H-exe，体磁各向异性常数2K（eff）/ M-0和表面钉扎已获得参数QL作为温度的函数。将结果与具有不同组成的NiMn合金的现有数据进行了比较。已经讨论了局部自旋涨落（LSF）对上述磁参数的温度依赖性的作用。 （C）1998 Elsevier Science B.V，保留所有权利。 [参考：27]

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