  In this work, fabrication and characterization of magnetic properties of
EuFe2As2 and EuRbFe4As4 single crystals is reported. Magnetization measurements
of samples with well defined thin film geometry and crystal orientation
demonstrate a striking similarity in ferromagnetic properties of Eu subsystems
in these two compounds. Measurements with magnetic field applied along ab
crystal planes reveal meta-magnetic transition in both compounds. Numerical
studies employing the Jz1-Jz2 Heisenberg model suggest that the ground state of
the magnetic order in Eu subsystem for both compounds is the helical spin order
with the helical angle about 2pi/5, while the meta-magnetic transition is the
helix-to-fan first order phase transition.
