Most magnetic materials host one or two types of magnon — collective spin excitations that propagate like waves through the lattice. You tune the field, the magnon frequency shifts, and the physics is predictable. Chromium oxychloride (CrOCl) breaks this pattern. Ren et al. (arXiv:2603.12865) show that sweeping the magnetic field through this van der Waals antiferromagnet produces an entire portfolio of distinct magnon branches, each appearing and disappearing at different field thresholds.
At low fields, the canted antiferromagnetic phase produces magnons shaped by strong bi-axial anisotropy. As the field increases, the system transitions through ferrimagnetic states that create two entirely new magnon branches. These partly coexist with the lower-energy canted-phase branch, meaning the material simultaneously hosts magnons from spatially separated magnetic phases — different regions of the same crystal hosting different magnetic orders at the same time.
The richness comes from competition. CrOCl has multiple exchange interactions pulling the spins in different directions, and several nearly degenerate ground states. The external field doesn't just tilt one order — it navigates between many, and the magnonic excitations at each stage reflect the local symmetry of whichever order currently wins.
A single material, a single knob (magnetic field), and a catalog of magnonic excitations. Most magnonics research engineers different materials for different magnon properties. CrOCl suggests the library is already present in one crystal — you just need to read different pages by turning the field to different strengths.
The portfolio metaphor is apt. Diversification in magnon types from a single source, where the mix depends on external conditions. The asset allocation is the physics.