  In this paper we report successful synthesis and magnetic properties of
(Ca,Na)(Zn,Mn)2Sb2 as a new ferromagnetic dilute magnetic semiconductor (DMS).
In this DMS material the concentration of magnetic moments can be controlled
independently from the concentration of electric charge carriers that are
required for mediating magnetic interactions between these moments. This
feature allows us to separately investigate the effect of carriers and of spins
on the ferromagnetic properties of this new DMS alloy, and particularly of the
critical ferromagnetic behavior. We use modified Arrott plot technique to
establish critical exponents b, g, and d of this alloy. We find that at low Mn
concentrations (< 10 at.%), it is governed by short-range 3D-Ising behavior,
with experimental values of b, g, and d very close to theoretical 3D-Ising
values of 0.325, 1.24, and 4.815. However, as the Mn concentration increases,
this DMS material exhibits a mixed-phase behavior, with g retaining its
3D-Ising characteristics, but b crossing over to longer-range mean-field
behavior.
