Progress in the Study of Unusually Large Anisotropic Magnetoresistance Effects
Our latest findings were published on August 25, 2009, in the Proceedings of the National Academy of Sciences. In cooperation with the National Institute of Materials Science of Japan, the Institute of Physics of the Chinese Academy of Sciences, Florida International University, and Louisiana State University, we have observed for the first time unusually large anisotropic magnetoresistance (Anisotropic Magnetoresistance) in perovskite-type manganese oxide single crystals. -AMR) effect, its value can reach more than 90%, which is nearly two orders of magnitude higher than the AMR effect in traditional ferromagnetic materials. Our study found that the anomalous AMR effect is closely related to the magnetic field-tunable metal-insulator transition in perovskite manganese oxides, thus providing a new idea for exploring new AMR materials and their applications.
In 1857, W. Thomson discovered that the resistivity of a material changes with the direction of the external magnetic field, a phenomenon known as the AMR effect. The AMR effect exists widely in various ferromagnetic materials, and has been widely used in read heads and magnetic sensors. Compared with giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), and colossal magnetoresistance (CMR) effects, the AMR effect in traditional ferromagnetic materials is small in value. For example, permalloy is a widely used AMR material, but its AMR value is only 1-2% at room temperature. due to lower sensitivity. In recent years, AMR devices are gradually being replaced by GMR and TMR devices. Our results show that in perovskite-type manganese oxide single crystals, even weak anisotropy can induce a very large AMR effect, which can even be higher than GMR and TMR, and the abnormal AMR effect is related to temperature has a non-monotonic relationship with the magnetic field. We propose a dimensional image model to give a good explanation for the above experimental results.
The research work was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences Innovation Team International Partnership Program, and the Zhejiang Province Outstanding Youth Team Project.
Resistance (left) and AMR (right) of perovskite manganese oxide La0.69Ca0.31MnO3 single crystal as a function of temperature and magnetic field
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