Magnetostrictive properties and detection efficiency of TbDyFe/FeCo composite materials for nondestructive testing

Abstract In order to develop a highly sensitive material for nondestructive testing (NDT), (Tb 0.3 Dy 0.7 )Fe 1.95 thin films were deposited on FeCo substrates at room temperature by magnetron sputtering and annealed. The magnetostrictive properties and the detection efficiency of the composite films were investigated. Results demonstrate that the detection efficiency roughly shows regular consistency with the magnetostrictive strain of the TbDyFe films. Heat treatment has a great effect on the crystalline state and the magnetostrictive strain of the composite materials. The as-deposited (Tb 0.3 Dy 0.7 )Fe 1.95 films are amorphous, and the saturation magnetostriction ( λ s ) is only 90 ppm. However, the nanostructured crystalline REFe 2 is partially separated out in amorphous matrix after annealing at 600 °C for 1 h, and the λ s increases to 265 ppm. Simultaneously, the detection efficiency of the composite materials is obviously improved compared to that of the as-deposited films. The detection signal of traditional FeCo strip is 0.4 V at the excitation power of 1.0 P and frequency of 128 kHz and that of the strip increases significantly by depositing one layer of (Tb 0.3 Dy 0.7 )Fe 1.95 film. The detection signal of the composite material annealed at 600 °C is the best, even reaching saturation value of 2.5 V (1.0 P, 128 kHz). The results may provide us with a method for preparing new materials for NDT.