Magnetic Dilution Study in La sub 2 Cu sub (1-x) (Mg or Zn) sub (x) O sub 4

Magnetic dilution effects in La sub 2 Cu sub (1-x) (Mg or Zn) sub (x) O sub 4 have been investigated through the measurements of Cu EPR signal, lattice parameters, transition temperature (T sub 0->T) from orthorhombic to tetragonal structure, and Neel temperature (T sub N). We found that lattice symmetry (orthorhombicity) and in-plane Cu-Cu distance are rather insensitive on the replacement of magnetic Cu ions by nonmagnetic Mg or Zn ions and that the weak reduction of T sub N by Mg or Zn substitution is comparable with that in other quasi-2D-Heisenberg magnets (for example, Rb sub 2 Cu sub (1-x) Mg sub (x) F sub 4 or K sub 2 Cu sub (1-y) (Mg or Zn) sub (x) F sub 4), which is in contrast to the rapid reduction of T sub N in oxygen- or divalent-ion-doped La sub 2 CuO sub 4.