Institute of Physics of the NAS of Ukraine, Kyiv 03680, Ukraine.
J Phys Condens Matter. 2013 Feb 13;25(6):066009. doi: 10.1088/0953-8984/25/6/066009. Epub 2013 Jan 11.
The mechanisms and properties of the equilibrium magnetization process for nanogranular films with perpendicular anisotropy placed in a tilted magnetic field are considered. The contributions of the effects of canting and flipping of the granules' magnetic moments to the process of film magnetization are studied. A critical behavior of the film magnetization at the transition, induced by a tilted magnetic field, from a state with non-uniform orientation of the granules' magnetic moments to one with a similar orientation is revealed. The results obtained within the two-level model of the orientation of the particles' magnetic moments are in good agreement with the experimental data for Co-Al(2)O(3) (61 at.% Co) granular film. The perpendicular anisotropy of the granules in this film originates mainly from their elongated shape. It is shown that in the non-uniform state the magnetostatic energy of a granular film with similarly oriented elongated granules can be described by the sum of contributions of two types: quasi-single-granular and quasi-film. The effective constant of the single-particle anisotropy of the granules in this case turns out to be dependent on the factor of volume filling of the film by granules, but not on its magnetization.
考虑了具有垂直各向异性的纳米颗粒薄膜在倾斜磁场中的平衡磁化过程的机制和特性。研究了磁各向异性的倾斜对颗粒磁矩倾斜和翻转效应在薄膜磁化过程中的贡献。揭示了在颗粒磁矩取向的两能级模型内，薄膜磁化在倾斜磁场诱导的从具有不均匀颗粒磁矩取向的状态到具有相似取向的状态的转变过程中的临界行为。对于 Co-Al(2)O(3)（61 原子% Co）纳米颗粒薄膜，获得的结果与实验数据非常吻合。该薄膜中颗粒的垂直各向异性主要源于其拉长的形状。结果表明，在非均匀状态下，具有相似取向的拉长颗粒的磁各向异性能可以通过两种类型的贡献之和来描述：准单颗粒和准薄膜。在这种情况下，颗粒的单粒子各向异性的有效常数取决于颗粒填充薄膜的体积填充因子，但与薄膜的磁化强度无关。
