層状構造La_<2-2x>Ca_<1+2x>Mn_2O_7の磁気状態図 (<特集>磁性体物理)

概要

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Polycrystalline samples of the layered perovskite La_2-_<2x>Ca_1+_<2x>Mn_2O_7 with quasi-two-dimensional Mn-O networks were synthesized, and a magnetic phase diagram obtained. La_2-_<2x>Ca_1+<2x>Mn_2O_7 has a two-type spin exchange interaction, one of which reflects the properties of the a-b plane, and the other properties of the c axis (out-of-plane) direction. As a result, for 0.22≦x≦0.5, there are three regions: PI (paramagnetic insulator), FI (ferromagnetic insulator), and FM (ferromagnetic metal). We observed a giant magnetoresistance (GMR) of Δρ/ρ_0 = 64% (77 K, 1.8 T, x = 0.25), which is much larger than that reported for the three-dimensional perovskite La_1-_xCa_xMnO_3. These results could be interpreted as due to anisotropic exchange interactions of La_2-_<2x>Ca_1+_<2x>Mn_2O_7.
社団法人日本磁気学会の論文
1997-04-15