A classification of magnetic superspace groups compatible with the helical and cycloidal magnetic modulations is presented. Helical modulations are compatible with groups from crystal classes 1, 2, 222, 4, 422, 3, 32, 6 and 622, while cycloidal modulations are compatible with groups from crystal classes 1, 2, m and mm2. For each magnetic crystal class, the directions of the symmetry‐allowed (non‐modulated) net ferromagnetic moment and electric polarization are given. The proposed classification of superspace groups is tested on experimental studies of type‐II multiferroics published in the literature.

中文翻译：

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不适用于螺旋和摆线调制的晶体对称性

提出了与螺旋和摆线磁调制兼容的磁超空间群的分类。螺旋调制与晶体等级1、2、222、4、422、3、32、6和622的组兼容，而摆线调制与晶体等级1、2，m和mm 2的组兼容。给出了对称允许（非调制）净铁磁矩和极化的方向。在文献中发表的II型多铁性化合物的实验研究中测试了提议的超空间组分类。