  Despite the blooming interest, the transition-metal rare-earth ferrimagnets
have not been comprehensively understood in terms of their coercivity and
transport properties. Here, we report a systematic study of the magnetic and
transport properties of ferrimagnetic FeTb alloy by varying the layer thickness
and temperature. The FeTb is tuned from the Tb-dominated regime to the
Fe-dominated regime via the layer thickness, without varying the composition.
The coercivity closely follows the $1/\cos\theta_H$ scaling (where $\theta_H$
is the polar angle of the external magnetic field) and increases
quasi-exponentially upon cooling (exceeding 90 kOe at low temperatures),
revealing that the nature of the coercivity is the thermally-assisted domain
wall depinning field. The resistivity exhibits a quasi-linear upturn upon
cooling possibly due to thermal vibrations of the structure factor of the
amorphous alloy. The existing scaling laws of the anomalous Hall effect in the
literature break down for the amorphous FeTb that are either Fe- or
Tb-dominated. These findings should advance the understanding of the
transition-metal-rare-earth ferrimagnets and the associated ferrimagnetic
phenomena in spintronics.
