  Bulk samples of La2.3-xYxCa0.7Mn2O7, x=0,0.3,0.5, with layered perovskite
structure have been synthesized and investigated with respect to their
electrical, electronic and magnetic properties. It is found that
La1.8Y0.5Ca0.7Mn2O7 has tetragonal structure and is a metallic ferromagnet with
a magnetic transition temperature of 170 K. The compound shows metallic
behavior below 140 K and has a large magnetoresistance (MR)
Delta-rho/rho(0)~94% at 100 K at 34 kOe. For x=0 and 0.3 the structure is
monoclinic with a suppression of metallicity. For x=0 the material is an
ferromagnetic insulator. We observed a large increase in the coefficient of the
linear term in specific heat with decreasing x. As far as we are aware, this is
the first report of an electron doped manganite showing metal-insulator
transition and ferromagnetism.
