The generation of a single-magnon state is one of the central goals in the emerging field of quantum magnonics. Here, we propose a simple protocol to achieve this goal in anisotropic ferromagnets, where the magnons naturally form an equilibrium-squeezed vacuum state. Applying a static magnetic field to the anisotropic ferromagnet, the ferromagnet will be prepared in a squeezed coherent state due to the displacement introduced by the static magnetic field. When the amplitude of the magnetic field is properly chosen, we show that the two-magnon occupation could be zero due to destructive interference between the displacement and squeezing, leaving a large probability for occupation in the single-magnon state. This is the so-called unconventional magnon blockade. Employing the second-order correlation function to characterize the statistical property of magnons, we find the unconventional magnon blockade is robust against the system's decay. This robustness comes from the equilibrium nature of magnon squeezing. Our study provides a possible strategy for generating a stable single-magnon source.

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• Magnons
• Quantum state engineering
• Spin waves
• Ferromagnets