  Recent experiments on Pd$_{3}$Fe intermetallics [Phys. Rev. Lett. 102, 237202
(2009)] have revealed that the system behaves like a classical invar alloy
under high pressure. The experimental pressure-volume relation suggests an
anomalous volume collapse and a substantial increase in bulk modulus around the
pressure where invar behavior is observed. With the help of first-principles
density functional theory based calculations, we have explored various magnetic
phases (ferromagnetic, fully and partially disordered local moment, spin
spiral) in order to understand the effect of pressure on magnetism. Our
calculations reveal that the system does not undergo a transition from a
ferromagnetic to a spin-disordered state as was thought to be the possible
mechanism to explain the invar behavior of this system. We rather suggest that
the anomaly in the system could possibly be due to the transition from a
collinear state to non-collinear magnetic states upon the application of
pressure.
