A comparative study of the magnetic and electrical properties of perovskite oxides and the corresponding two-dimensional oxides of K₂NiF₄ structure

Abstract

Electrical and magnetic properties of several oxide systems of K₂NiF₄ structure have been compared to those of the corresponding perovskites. Members of the La_1−xSr_1+xCoO₄ system are all semiconductors with a high activation energy for conduction unlike La_1−xSr_xCoO₃ (x≥0.3) which is metallic; the latter oxides are ferromagnetic. La_0.5Sr_1.5CoO₄ shows a magnetization of 0.5 μ_B at 0 K (compared to 1.5 μ_B of La_0.5Sr_0.5CoO₃), but the high-temperature susceptibilities of the two systems are comparable. In SrO·(La_0.5Sr_0.5MnO₃)_n, both magnetization and electrical conductivity increase with the increase in n approaching the value of the perovskite La_0.5Sr_0.5MnO₃. LaSrMn_0.5Ni_0.5(Co_0.5)O₄ shows no evidence of long-range ferromagnetic ordering unlike the perovskite LaMn_0.5Ni_0.5(Co_0.5)O₃; high-temperature susceptibility behavior of these two insulating systems is, however, similar. LaSr_1−xBa_xNiO₄ exhibits high electrical resistivity with the resistivity increasing proportionately with the magnetic susceptibility (note that LaNiO₃ is a Pauli-paramagnetic metal). High-temperature susceptibility of LaSrNiO₄ and LaNiO₃ are comparable. Susceptibility measurements show no evidence for long-range ordering in LaSrFe_1−xNixO₄ unlike in LaFe_1−xNi_xO₃ (x≤0.35) and the electrical resistivity of the former is considerably higher. Electrical resistivity of Sr₂RuO₄ is more than an order of magnitude higher than that of SrRuO₃. Some generalizations of the properties of two- and three-dimensional oxide systems have emerged from these experimental observations.