LETTER TO THE EDITOR: Temperature-tuned natural ferromagnetic resonances in ?

We present the results of an investigation into the zero-field microwave absorption in for frequencies ranging from 2 to 35 GHz. The temperature dependence of the microwave loss at zero applied field displays two peaks for frequencies less than 15 GHz. These peaks can be ascribed to temperature tuning of the internal anisotropy field to satisfy the conditions for ferromagnetic resonance.