Rekayasa Struktur dan Sifat Material Komposit sistem Ba0.5Sr0.5Fe12-xMnx/2Tix/2O19-La0,7Ba0,3MnO3 (x = 0; 0.1; 0.2; 0.3; 0.4; 0.5) sebagai Penyerap Gelombang Elektromagnetik = Modified structures and material properties for composite system based on Ba0.5Sr0.5Fe12-xMnx/2Tix/2O19-La0.7Ba0.3MnO3 (x = 0; 0.1; 0.2; 0.3; 0.4; 0.5) as electromagnetic wave absorber