Whereas dc measurements of magnetic susceptibility, χ, fail to distinguish between local and weak itinerant ferromagnets, radio-frequency (rf) measurements of χ in the ferromagnetic state show dramatic differences between the two. We present sensitive tunnel-diode resonator measurements of χ in the weak itinerant ferromagnet ZrZn2 at a frequency of 23 MHz. Below Curie temperature, TC ≈ 26 K, th...
