High-field anomalies of equilibrium and ultrafast magnetism in rare-earth--transition-metal ferromagnets

Physical Review B: Condensed Matter and Materials Physics. 2019. Vol. 100. P. 174427.

Zvezdin A.

Magneto-optical spectroscopy in fields up to 30 T reveals anomalies in the equilibrium and ultrafast magnetic properties of the ferrimagnetic rare-earth–transition-metal alloy TbFeCo. In particular, near the magnetization compensation temperature, each of the magnetizations of the antiferromagnetically coupled Tb and FeCo sublattices show triple hysteresis loops. Contrary to state-of-the-art theory, which explains such loops by sample inhomogeneities, here we show that they are an intrinsic property of the rare-earth ferrimagnets. Assuming that the rare-earth ions are paramagnetic and have a nonzero orbital momentum in the ground state and, therefore, a large magnetic anisotropy, we are able to reproduce the experimentally observed behavior in equilibrium. The same theory is also able to describe the experimentally observed critical slowdown of the spin dynamics near the magnetization compensation temperature, emphasizing the role played by the orbital momentum in static and ultrafast magnetism of ferrimagnets.

Keywords: ferromagnetism, ферромагнетизм