Effect of Slow Ion Relaxation at Ferromagnetic Resonance in a CoFeB-LiNbO Metal-Insulator Nanocomposite

Metal-insulator nanocomposite (CoFeB) x (LiNbO 3 ) 1− x films are studied by the ferromagnetic resonance method in the temperature range of 4–320 K. In the low-temperature region, the maximum of the ferromagnetic resonance linewidth and a negative dynamic shift of the absorption peak, typical of the mechanism of slow ion relaxation on magnetic impurities, are found. The observed magnetic relaxation features can be caused by paramagnetic Co and Fe ions, which are dispersed in the dielectric LiNbO 3 matrix and are exchange-coupled to ferromagnetic CoFeB granules. Experimental temperature dependences of the ferromagnetic resonance linewidth and shift are in good agreement with theoretical curves obtained within the proposed approach.