超巨磁阻测辐射热仪

COLOSSAL MAGNETORESISTANCE BOLOMETER 

基于超巨磁阻 (CMR)材料在金属 绝缘体 (M I)转变点附近的巨大电阻变化 ,设计并测试了一种新型超巨磁阻测辐射热仪 (CMRbolometer) .用外延法生长的La0 .67Ca0 .3 3 MnO3薄膜作为测辐射热仪的辐射敏感元件 ,测量了该器件对黑体和He Ne激光器的光学响应 .所测的信号、噪声都随调制频率的上升而下降 ,但对于He Ne激光源 ,它的信噪比却没有明显的改变 .测量了薄膜铁磁金属态和顺磁绝缘态的信号 温度关系 ,最强的信号出现在靠近M I转变点 (居里点 )附近的铁磁态范围 .由于薄膜的居里点温度TC 随制备条件的不同 ,可从 70K变化到 35 0K ,所以该器件的最大特点是能在室温下工作 .从这个角度看 ,它可弥补高温超导测辐射热仪只能工作于液氮温区的缺点 .初步测量显示 ,该器件的探测率接近 10 7cmHz1/ 2 W-1,热响应时间约为 2 0ms.与高温超导测辐射热仪相比 ,超巨磁阻测辐射热仪的时间常量偏大 ,探测率偏低 .然而 。

Based on the sharp resistance change near the metal\|insulator transition (M\|I) of the colossal magnetoresistance (CMR) materials, we design and test a new type CMR bolometer. La 0.67 Ca 0.33 MnO 3 epitaxial thin films were used as the photosensitive element of the bolometer, and the optical response of this device to the He\|Ne laser and the blackbody were measured. The measured signal and noise decrease with increasing modulation frequency; however, the signal\|to\|noise ratio shows no obvious change for the He\|Ne laser. The temperature dependence of signal was measured in both ferromagnetic metallic and paramagnetic insulating states. It shows that the strongest signal appears in the ferromagnetic state very close to the M\|I point. The film's Curie temperature can span from 70 to 350?K, depending on the manufacture conditions. So, working near or at room temperature characterizes this CMR thin film bolometer. In this sense, it compensates the weakness of the high\|temperature superconductor bolometer that can be used only around the liquid Nitrogen (LN) temperature. The measured detectivity is about 10 7 cmHz 1/2 /W and the thermal response constant is 20ms for this device. Compared with the high\|temperature superconductor bolometer, the time constant of CMR bolometer is longer and the detectivity is lower. However, there is much room to improve yet.