Micromagnetic Exchange Coupled Hard / Soft Multilayer System

The multilayer exchange-spring magnets are noticed new materials, which were developed at the beginning of 1990s. The magnets can become a kind of high performance magnetic materials owing to high energy products and the possibility of being integrated in electronic devices. In this thesis, we do some research on the multilayer exchange-spring magnets based micromagnetic, as follows:(1) In this thesis, we have programed micromagnetic applied software on the basic of the micromagnetic theory, which is used mostly to simulate nanomagnets.(2) Studing the effects of the exchange coupling at the interfaces on the magnetic performance. The results show that the exchange coupling at the interfaces affect the magnetic performance of system greatly, the remanence and the intrinsic coercive field increase quickly initially, then reach saturation gradually.(3) Studing the effects of structure dimension on the magnetic performance. The results show that (a) The thickness of soft layer affect the magnetic performance of system greatly. The remanence enhances with the increase of the thickness of soft layer initially, then decreases gradually, while the thickness of soft layer reach some value. In the one-dimension quasi-static modal, the intrinsic coercive field decreases with increasing the thickness of soft layer, however, in the three-dimension dynamic modal, the intrinsic coercive field enhances with the increase of the thickness of soft layer initially, then decreases gradually while the thickness of soft layer reach some value. The maximum energy produce enhances with the increase of the thickness of soft layer initially, then decreases gradually while the thickness of soft layer reach some value, (b) The thickness of hard layer affect also the magnetic performance of system to some degree. With increasing the thickness of hard layer, both the remanence and the maximum energy produce decreases. For the thinner soft layer, the intrinsic coercive field enhances with increasingthe thickness of hard layer, however, when the thickness of soft layer is thicker, the changes of the intrinsic coercive field is ambiguity.(4) The results of the three-dimension dynamic simulation show: For layer thickness values less than the critical thickness( the two phases are rigidly coupled), The magnetization reversible process of the two layer are the consistent rotation of the magnetic moment. However, if the two layers are thicker, in the surface of film, the reversible process of the soft layer is complicated and the reversible process of the hard layer is to form nucleus on the boundary, then the nucleus displaces to the center of the surface of film. We find there are some relations between the thickness of hard layer and the critical dimension of the soft layer.(5) By studing the multilayer exchange-spring magnets of period and quasi-period structure, the total thickness of which is fixed, we find: the number of layer has great effect on the magnetic performance. Which is a directive meaning to the preparation of the multilayer exchange-spring magnets.