固相反应法制备La_(0.6)Sr_(0.25)K_(0.15)MnO_3+xAg复合材料及其磁电阻效应研究

Study on Magnetoresistance Effect of La_(0. 6)Sr_(0. 25)K_(0. 15)MnO_3+xAg Composite Prepared by Solid State Reaction

采用固相反应法使提前制备好的La0．6Sr0．25K0．15MnO3与AgNO3复合，制备了La0．6Sr0．25K0．15MnO3＋xAg（x=0．04，0．06，0．08）系列复合样品。我们在样品的相结构、磁性质及其磁电阻效应方面进行了研究。通过相结构的研究发现：复合样品中除了有钙钛矿主相外还有少量Ag相和Mn3O3相。通过对样品的磁性测量发现：复合样品对母体样品的比饱和磁化强度和居里温度的影响很小。复合后，母体样品的磁电阻温度稳定性得到很好改善。当x=0．04时，在290—352K的温度范围内，磁电阻值稳定在5．0％±0．2％；当x=0．06时，在260—307K的温度范围内，磁电阻值保持在3．8％±0．2％；在282～339K内x=0．08的复合样品的磁电阻值保持在5．03％±0．12％。本征磁电阻与隧穿磁电阻竞争的结果是导致磁电阻值的温度稳定性的机制。

A series of samples La0.6Sr0.25K0.15MnO3＋xAg（x = 0, 0.04, 0.06, 0.08） were prepared by solid state reaction. Phase structure, magnetic properties and magnetoresistance effect were studied. Through the study of the phase structure, it has been found that the samples present La0.6 Sr0.25 K0.15 MnO3 Ag/Mn3O4. The magnetic measurements on samples revealed that the composition of samples has almost no effect on the saturation magnetization and Curie temperature. Temperature stability of magnetic resistance for the matrix samples was well improved by compositing Ag. In the temperature range of 290-352 K and under the 1.8 T external magnetic field, when x = 0. 04, MR maintained at 5.0% ± 0. 2%. In the temperature range of 260-307 K ,when x =0.06, MR maintained at 3.8% ±0.2%. When x =0.08, in the temperature range of 282-339 K , MR maintained at 5.03%± 0.12%. The temperature range is so wide, that it is very good for the practical application of MR. Mechanism of temperature stability of MR is the result of competition between the intrinsic magnetoresistance and the tunneling magnetoresistance.