La_(0.67)Ca_(0.33)MnO_(3-δ)体材料的巨磁电阻特性

GIANT MAGNETORESISTANCE PROPERTIES OF La 0.67 Ca 0.33 MnO 3-δ BULK MATERIALS

利用高温烧结法制备了多晶立方结构的Ｌａ０．６７Ｃａ０．３３ ＭｎＯ３－δ体材料。材料的居里温度（ＴＣ）为２８０Ｋ，其金属半导体转变温度（Ｔｐ） 为２７０Ｋ，接近于ＴＣ。外加磁场下的磁电阻（ＭＲ） 峰值温度与Ｔｐ 十分接近。外加磁场为０．６Ｔ 和５Ｔ时，材料的ＭＲ 峰置分别达到４０％ 和７６％ 。材料具有显著的巨磁电阻效应。在液氮温度附近，也观察到了相当大的磁电阻效应。利用高温烧结法制备了多晶立方结构的Ｌａ０．６７Ｃａ０．３３ ＭｎＯ３－δ体材料。材料的居里温度（ＴＣ）为２８０Ｋ，其金属半导体转变温度（Ｔｐ） 为２７０Ｋ，接近于ＴＣ。外加磁场下的磁电阻（ＭＲ） 峰值温度与Ｔｐ 十分接近。外加磁场为０．６Ｔ 和５Ｔ时，材料的ＭＲ 峰置分别达到４０％ 和７６％ 。材料具有显著的巨磁电阻效应。在液氮温度附近，也观察到了相当大的磁电阻效应。

Cubic polycrystalline bulk materials of La 0.67 Ca 0.33 MnO 3-δ were synthesized by sintering at high temperature. The samples showed a metal semiconductor transition at 270K, which was close to their Curie temperature, T C , 280K. The magnetoresistance (MR) peak temperature appeared at the temperature very close to T p . The MR peak value reached 76% under 5·10 4Oe field, and still reached 40% under a low field of 6·10 3Oe, both indicating a notable giant magnetoresistance (GMR) effect. There still existed relatively large MR effect at low temperatures near 77K, which was related to the transport behavior of the carriers near the grain boundaries.