Investigation on magnetic properties of parallel and perpendicular oriented Nd₂Fe₁₄B/Fe₆₅Co₃₅/Nd₂Fe₁₄B films by the micro-magnetism finite element method

In present study, the hysteresis loops and the magnetic reversal process of both the parallel and the perpendicular oriented Nd₂Fe₁₄B/Fe₆₅Co₃₅/Nd₂Fe₁₄B trilayers with different soft phase thicknesses were studied by the micro-magnetism finite element method. Analysis of magnetization vectors' evolution in demagnetization process indicates that the parallel and the perpendicular oriented trilayers exhibit different magnetic reversal behaviors. All the demagnetization curves of the perpendicular oriented trilayers exhibits "single phase" behavior, while noticeable kinks presents in the demagnetization curves of the parallel oriented trilayers with the soft phase thickness equal to or larger than 12 nm. Moreover, as the thickness of the soft phase increases, the remanence (Br) of the parallel and the perpendicular oriented trilayers increases first, peaks respectively at 1.90 and 1.93 T, respectively, and then decreases again. On the other hand, the coercivity (μ₀H_c) of the parallel and the perpendicular oriented trilayers drops monotonically with the increase of soft layers thickness. As a result, the optimal maximum energy product [(BH)_max] of the parallel and the perpendicular oriented trilayers are 630 kJ/m³ and 592 kJ/m³, respectively. Deviation degree of orientation was simulated for the perpendicular oriented trilayers with Ls=10 nm. - Highlights: • The magnetic properties of Nd₂Fe₁₄B/Fe₆₅Co₃₅/Nd₂Fe₁₄B trilayers were simulated. • Magnetization vectors' evolution in demagnetization process was analyzed. • Deviation degree of orientation was added in the simulation