Identifying efficient pathways to control and modify the order parameter of a macroscopic phase in materials is an important ongoing challenge. One way to do this is via the excitation of a high-frequency mode that couples to the order, and this is the ultimate goal of the field of ultrafast phase transitions^1,2. This is an especially interesting research direction in magnetism, where the coupling between spin and lattice excitations is required for magnetization reversal^3,4. However, previous attempts^5,6 have not demonstrated switching between magnetic states via resonant pumping of phonon modes. Here we show how an ultrafast resonant excitation of the longitudinal optical phonon modes in magnetic garnet films switches magnetization into a peculiar quadrupolar magnetic domain pattern, revealing the magneto-elastic mechanism of the switching. In contrast, the excitation of strongly absorbing transverse phonon modes results in a thermal demagnetization effect only.

确定有效的途径来控制和修改材料中宏观相的有序参数是一项重要的持续挑战。一种方法是通过激发耦合到顺序的高频模式，这是超快相变^1,2领域的最终目标。这是磁性中一个特别有趣的研究方向，其中自旋和晶格激发之间的耦合是磁化反转^3,4所必需的。然而，以前的尝试^5,6还没有证明通过声子模式的共振泵浦在磁态之间切换。在这里，我们展示了磁性石榴石薄膜中纵向光学声子模式的超快共振激发如何将磁化转换为特殊的四极磁畴模式，揭示了转换的磁弹性机制。相反，强吸收横向声子模式的激发仅导致热退磁效应。