A comparative study of the magnetic and electrical properties of perovskite oxides and the corresponding two-dimensional oxides of K 2NiF 4 structure
Electrical and magnetic properties of several oxide systems of K 2NiF 4 structure have been compared to those of the corresponding perovskites. Members of the La 1- xSr 1+ xCoO 4 system are all semiconductors with a high activation energy for conduction unlike La 1- xSr xCoO 3 ( x ≥ 0.3) which is metallic; the latter oxides are ferromagnetic. La 0.5Sr 1.5CoO 4 shows a magnetization of 0.5 μ B at 0 K (compared to 1.5 μ B of La 0.5Sr 0.5CoO 3), but the high-temperature susceptibilities of the two systems are comparable. In SrO · (La 0.5Sr 0.5MnO 3) n, both magnetization and electrical conductivity increase with the increase in n approaching the value of the perovskite La 0.5Sr 0.5MnO 3. LaSrMn 0.5Ni 0.5(Co 0.5)O 4 shows no evidence of long-range ferromagnetic ordering unlike the perovskite LaMn 0.5Ni 0.5(Co 0.5)O 3; high-temperature susceptibility behavior of these two insulating systems is, however, similar. LaSr 1- xBa xNiO 4 exhibits high electrical resistivity with the resistivity increasing proportionately with the magnetic susceptibility (note that LaNiO 3 is a Pauli-paramagnetic metal). High-temperature susceptibility of LaSrNiO 4 and LaNiO 3 are comparable. Susceptibility measurements show no evidence for long-range ordering in LaSrFe 1- xNi xO 4 unlike in LaFe 1- xNi xO 3 ( x ≤ 0.35) and the electrical resistivity of the former is considerably higher. Electrical resistivity of Sr 2RuO 4 is more than an order of magnitude higher than that of SrRuO 3. Some generalizations of the properties of two- and three-dimensional oxide systems have emerged from these experimental observations.