Quantitative analysis of spin wave dynamics in ferrimagnets across compensation points

Rare-earth transition-metal ferrimagnets have two strongly coupled sublattices of distinct chemical nature, which give rise to complex and fast dynamics great interest spintronics. However, the remains less understood than ferromagnets. We measure spin wave (SW) spectra a GdFeCo film by Brillouin light scattering spectroscopy (BLS) across its compensation temperatures---temperatures at either sublattices' magnetizations or their angular moments cancel out, mimicking an antiferromagnet. find SW modes per vector with thermal dependencies, cross field-dependent temperature. develop analytical model based on corresponding rare earth transition metal, reproduces quantitatively evolution temperature field. This validates proposed energy dynamical ferrimagnet, demonstrates usefulness BLS in study this promising class materials.