Thermal investigations of the acoustic emission in polycrystalline ferrimagnets

Acoustic emission (AE) has been studied along hysteresis loops from 77 K up to the Curie temperature T_c on a YIG and on a Ni-Zn ferrite. It is found that the AE activity is proportional to the hysteresis losses, which confirms previous measurements at room temperature on a larger set of materials, and which reinforces the idea that domain wall creation/annihilation is the origin of both AE and hysteresis losses. The temperature dependence of the AE is interpreted in terms of a frequency shift of the AE spectrum and of self-absorption/dispersion of the AE by the domain walls and/or by the diffusion centers