High frequency ESR studies of kagome antiferromagnets

Ba/sub 2/Sn/sub 2/Ga/sub 3/ZnCr/sub 7/O/sub 22/ is pyrochlore slab antiferromagnets and exhibits a strong frustration. The pyrochlore slab lattice consists of two 2D-kagome layers which sandwiches a triangular layer in between. In order to investigate the magnetic behaviors, high frequency ESR measurements of the diluted Ba/sub 2/Sn/sub 2/Ga/sub 10-7p/ZnCr/sub 7p/O/sub 22/ have been performed in the millimeter wave region (120 GHz and 228 GHz) at the temperatures from 4.2 K to 200 K. The concentration dependences of Cr/sup 3+/ magnetic ions were observed from p=0.01 p=1.