抄録
Perovskite-type RE2/3AE1/3MnO3(RE=La, Pr; AE=Ca, Sr, Ba) ceramics were fabricated by a conventional ceramics technique, and their magnetic properties and magnetoresistance effect were measured. The Curie temperatures of all the studied samples were about 77 K, and in particular, that of La2/3Sr1/3MnO3, La2/3Ba1/3MnO3, Pr2/3Sr1/3MnO3 was above room temperature. The typical magnetic properties obtained from the magnetization curves measured at 77 K were Ms≈70-80 emu/g, Mr≈ 10 emu/g, and iHc ≈200 Oe.The temperature at which the ρ-T curves reached a maximum was about 50 K lower than their Curie temperature. The MR ratio of each sample was about -20∼-40% in the measurement conditions where T=77 K and H=15 kOe. At room temperature. three kinds of sample whose Curie temperature exceeded room temperature had an MR ratio of about -10%. whereas the rest of the samples had MR ratios of less than - 1%.
