We present the frequency dependence of microwave-absorbing properties of La
1-xSrxMnO3 (x=0.4, 0.5, 0.6, and 0.7) powders at room temperature. The abso
rbing properties change gradually with x in the frequency range of 8-12 GHz
. The optimal absorption can be achieved for a x=0.4 sample and its microwa
ve loss peak value is about 25 dB. Further experimental results show that t
he absorption can be attributed to magnetic and dielectric losses and the m
icrowave loss peak corresponds to the maximum dielectric loss tangent tan d
elta (e) near 10.5 GHz. Furthermore, the absorbing properties of the oxides
mixed with carbonic fiber and Y-type planar hexagonal ferrite have been ru
dimentarily studied. Results show that these additives greatly enhance the
microwave-absorbing properties of the oxides. (C) 2001 American Institute o
f Physics.