Giant radio-frequency magnetoabsorption effect in the cobaltite ceramic La0.5Sr0.5CoO3

The DC transport properties of and the radio-frequency (RF) wave absorption (at 1.33 MHz) in a ceramic sample of La0.5Sr0.5CoO3-delta are measured. The Curie temperature T-c of the sample is about 250 K. A giant negative magnetoabsorption effect is found. In the vicinity of T-c, the absolute value of the magnetoabsorption is about 38% in the rather low magnetic field 2.1 kOe. This differs drastically from the measured DC magnetoresistance (MR) delta(H)=[R(0)-R(H)]/R(0) which is a mere 0.26% near T-c in the same field and increases to about 2.15% in H=20 kOe. The phenomenon can be understood taking into account that the magnetoabsorption is determined by influence of magnetic field on the conductivity and the magnetic permeability, while the MR is determined solely by the former. The magnetoabsorption effect can be used to develop RF devices controlled by magnetic field and temperature. (C) 2003 American Institute of Physics.