A NEW TECHNIQUE TO ASSESS ELECTRICAL BEHAVIOR BY MICROWAVE MEASUREMENTS, APPLICATION TO PEROVSKITES RNIO(3) (R=ND, SM)

An original technique to measure conductivity and Hall effect on powde red samples at microwave frequency is presented. A microwave electric field (E) over right arrow and a perpendicular magnetic field (B) over right arrow induce an effect on the motion of electric charges and a component of the movement appears along the direction (E) over right a rrow A (B) over right arrow. This motion generates, in a cavity, a new mode of oscillation. The analysis of the signal allows the study of t he charge carriers, especially the sign and the parameters tau/m and n . This new method has been used to measure the conductivity behaviour of perovskites Sm1-xNdxNiO3. It proved possible to detect the metal-in sulator transition at room temperature, as well as the nature of charg e carriers. (C) 1997 Elsevier Science Ltd.