Electromagnetic-wave/ferromagnetic-material studies with magneto-optics are active, having the applications in magneto-optic recording, computer data-storage, waveguides, etc. In this paper, we investigate a variable-coefficient modified Kadomtsev–Petviashvili system for the electromagnetic waves in an isotropic charge-free infinite ferromagnetic thin film with the potential application in magneto-optic recording. With respect to the electromagnetic waves in the ferromagnetic film, symbolic computation helps us work out (1) two sets of the variable-coefficient-dependent auto-Bäcklund transformations via the generalized Laurent series in the neighborhood of the non-characteristic singular manifold, along with some solitonic features, (2) the variable-coefficient-dependent bilinear forms and (3) two branches of the variable-coefficient-dependent $N$-solitonic solutions with $N$ being a positive integer. Relevant constraints on the variable coefficients are presented. We hope that the results could be of some use in magneto-optic recording, computer data-storage and waveguides.

磁光的电磁波/铁磁材料研究很活跃，在磁光记录、计算机数据存储、波导等方面都有应用。各向同性无电荷无限铁磁薄膜中的电磁波在磁光记录中的潜在应用。关于铁磁薄膜中的电磁波，符号计算帮助我们计算出 (1) 通过非特征奇异流形邻域中的广义洛朗级数，沿具有一些孤子特征，（2）依赖于变量的双线性形式和（3）依赖于变量的两个分支$N$-孤子解决方案 $N$是一个正整数。给出了对可变系数的相关约束。我们希望结果可以在磁光记录、计算机数据存储和波导方面有所帮助。