Abstract: The present invention relates to compounds represented by the formula: ##STR1## wherein R.sup.1 is (1) an optionally substituted alkyl group which may be bonded through a hetero atom, (2) an optionally substituted acyl group, (3) an alkylsulfonyl group, (4) an alkylsulfinyl group, or (5) an optionally substituted sulfamoyl group; A is --N.dbd. or -CH.dbd.; R.sup.2 is a hydrogen atom or an alkyl group which may optionally be substituted with halogen and which may be bonded through a hetero atom;X.sup.1 is halogen or a lower alkyl group;X.sup.2 is a hydrogen atom or a fluorine atom;R.sup.3 is a hydrogen atom, halogen or a lower alkyl group;and R.sup.4 is a hydrogen atom, an optionally substituted alkyl group or an acyl group, provided that when R.sup.1 is (1) a C.sub.1-4 alkanoyl group, (2) benzoyl, (3) trifluoroacetyl, (4) sulfamoyl which may optionally be substituted with a C.sub.1-4 alkyl group, (5) a C.sub.1-4 alkyl group which may optionally be substituted with hydroxy, halogen or a C.sub.

Abstract: A wave absorber is provided which has a wave absorption characteristic of 20 dB in a frequency band of 1 GHz to 20 GHz, is nonflammable, compact and lightweight, and has excellent durability. A porous ferrite is produced as the base material for which is an Ni--Zn type ferrite which has an excellent wave absorption characteristic in the high frequency range, and this serves as a wave absorber formed in the shape of a pyramid or triangular prism.