Magnetic properties of ndfeb thin films grown by a pulsed laser deposition

Abstract

High energy product Nd₂Fe₁₄B films were grown onto Si(100) substrate by a KrF pulsed laser ablation using the targets of Nd_xFe_90.98-xB_9.02 (x=17.51~27.51). The films of the Nd₂Fe₁₄B single phase did not exhibit a preferred orientation. However, [221], [006] and [222] axes were prominent for the films grown at the substrate temperature above 680°C by using the target of Nd_27.51Fe_63.47B_9.02. This condition provided superior magnetic properties along the out-of-plane direction of films resulting in the magnetic properties of 4πM_s≅7 kG, 4πM_r≅4 kG, and iH_c≅1000 Oe. The deposition rate wasn’t influenced much by changing the substrate temperature (T_s), but it increased linearly by increasing the beam energy density. The beam density of 3 J/ cm² created the optimal condition for the highest 4πM_r andiH _c simultaneously. The higher content of Nd induced a higher coercivity and concentration of 4πM_r at the same time due to the finer grain size without a prominent change in 4πM_s. The films of x=27.51 exhibited a grain size of less than 12 nm while that of x= 17.51 produced a size about 15 nm.