硬/软磁复合材料的一致转动模型及其磁滞回线

Coherent Rotation Model and Hysteresis Loops of Hard/Soft Magnetic Composite Materials

运用微磁学方法讨论了Stoner-Wohlfarth(SW)模型中单畴粒子的矫顽力、临界场、磁滞回线及其磁能积.当外场与粒子易磁化轴的夹角α≤45°时,矫顽力等于临界场;当α>45°时,矫顽力比临界场小得多.将SW模型简化成更简单的一致转动模型,计算了由硬磁、软磁两相构成的复合双层膜.计算结果表明,当硬软磁两相的易磁化轴都与外磁场平行(α=0°)时,对于λ(=Ks/Kh)值,其磁滞回线为矩形,即临界场等于矫顽力.随着λ的增大,矫顽力和临界场都增大;当外磁场与硬磁相的易轴平行,与软磁相的易轴垂直(α=90°)时,磁滞回线还是矩形的,但矫顽力和临界场随着λ的增大而减小.

Coercivity, critical magnetic field, hysteresis loop and energy product of the isolated crystallite in the Stoner-Wohlfarth （SW） model have been calculated using a micromagnetic approach. For α≤45°, which is the angle between the applied magnetic field and easy axis, the coercivity equals to the critical field, while tbe coercivity is much smaller than the critical field for α〉45°. And then, SW model is simplified to a more brief coherent rotation model, where the coercivity and the critical field of the hard/soft magnetic composite bilayers have been calculated. It is found that when both of the e axes for the hard and soft magnetic phases are parallel to the applied magnetic field （ α= 0°）, hysteresis loops are rectangular for the same λ（ =K^s/K^k ）, i.e. , the critical field equals to the coercivity. In addition, both of critical field and coercivity go up as λ increases. When the applied magnetic field is parallel to the easy axis in the hard magnetic phase and perpendicular to that in the soft one （α= 90°）, hysteresis loops are still rectangular, but critical field and coercivity decrease with the increasing of λ.