EFFECT OF PERCOLATION IN AN INTERGROWTH STRUCTURE

The three systems LaSrAl1-xNixO4, LaSrAl1-xFexO4 and LaSrFe1-xNixO4 have the tetragonal K2NiF4 structure and a two-dimensional percolation limit xc approximately=0.59. A tolerance factor t>1 in LaSrAlO4 creates a large c/a axial ratio due to relief of compressive stress in the rocksalt layer. LaSrNiO4 contains low-spin Ni(III) with one itinerant sigma *(x2-y2) electron per Ni atom. LaSrFeO4 is an antiferromagnet with high-spin Fe3+ ions. For x xc. In LaSrFe1-xNixO4, the low-spin Ni(III) ions have a 3d(x2-y2) orbital more stable than the 3d(z2) orbital for all x, and antiferromagnetic coupling occurs for all x