The magnetic-field-driven effect of microwave detection in a manganite granular system

Abstract

We demonstrate the microwave detection effect in a granular La0.7Ca0.3MnO3 sample. Dc voltage generated by the sample in response to microwave irradiation below the Curie temperature is found to be dependent on the applied magnetic field. The magnetic field dependence of the dc voltage has a broad peak resembling an absorption line. The detection effect depends substantially on the magnetic history of the sample; however, identical measurement conditions provide reproducibility of the experimental results. The detected dc voltage increases linearly with microwave power and strongly depends on a bias current through the sample. According to the results of systematic measurements, there exist two contributions to a value of the detected output signal. The first is magneto-independent; it can be explained in the framework of a mechanism used traditionally for description of the rectification effect in metal–insulator–metal junctions with nonmagnetic metals. The other is magneto-dependent; it originates from the interplay between the spin-dependent current through magnetic tunnel junctions and spin dynamics of the grains, which form these junctions in the sample.

Magnetically driven high-frequency rectification in a cooperative system of magnetic tunnel junctions: Frequency dependence

“…What may be expected in the case of a cooperative system of the magnetic tunnel junctions? We observed the magnetically controlled effect of microwave radiation detection in a manganitebased granular material representing a ramified network of the magnetic tunnel junctions [4]. Similar to the case of a single tunnel junction, rectification of the high-frequency current is related to the polarized current through the boundaries between ferromagnetic grains, which serve as the magnetic tunnel junctions.…”

“…As in the previous study [4], we investigated La 0.7 Ca 0.3 MnO 3 samples prepared by a conventional solid state reaction method. Technological details, results of X-ray diffraction and scanning and transmission electron microscopic characterization of the samples, and data on their transport and magnetic properties were reported previously [4].…”

“…Technological details, results of X-ray diffraction and scanning and transmission electron microscopic characterization of the samples, and data on their transport and magnetic properties were reported previously [4]. Magnetic field dependences of magnetization presented here were measured using a vibrating sample magnetometer.…”

“…The detection effect, i.e., the occurrence of a constant voltage in a sample under the action of microwave radiation was measured using the experimental scheme described in [4], but in our case, instead of placing it into a resonator, the sample was fixed at the end of a bridged waveguide line operating in a TE 10 mode. This allowed investigations at different frequencies of microwave radiation as the sample was always in an antinode of the magnetic component of an electromagnetic field.…”

Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation

“…This system exhibits a great value of magnetoresistance and the magnetic-field-driven microwave detection effect [14,15]. The magnetoresistance and rectification effects in the granular manganite sample are caused by a ramified network of the magnetic tunnel junctions, which are formed by ferromagnetic conducting grains with insulator boundaries.…”