  The DC transport properties of and the radio-frequency (RF) wave absorption
(at 1.33 MHz) in a ceramic sample of La_{0.5}Sr_{0.5}CoO_{3-\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.
