  Ferrimagnetic alloys are extensively studied for their unique magnetic
properties leading to possible applications in perpendicular magnetic
recording, due to their deterministic ultrafast switching and heat assisted
magnetic recording capabilities. On a prototype ferrimagnetic alloy we
demonstrate fascinating properties that occur close to a critical temperature
where the magnetization is vanishing, just as in an antiferromagnet. From the
X-ray magnetic circular dichroism measurements, an anomalous 'wing shape'
hysteresis loop is observed slightly above the compensation temperature. This
bears the characteristics of an intrinsic exchange bias effect, referred to as
atomic exchange bias. We further exploit the X-ray magnetic linear dichroism
(XMLD) contrast for probing non-collinear states which allows us to
discriminate between two main reversal mechanisms, namely perpendicular domain
wall formation versus spin-flop transition. Ultimately, we analyze the
elemental magnetic moments for the surface and the bulk parts, separately,
which allows to identify in the phase diagram the temperature window where this
effect takes place. Moreover, we suggests that this effect is a general
phenomenon in ferrimagnetic thin films which may also contribue to the
understanding of the mechanism behind the all optical switching effect.
