Sdudy On Interface Structure Of Nanocomposite Permanent Magnetic Materials

Nanocomposite permanent material which having both high coercivity and magnetization possesses a high theoretical energy product, gaining rapid development in the last two decades. The main reason is the presence of exchange coupling that leads to remanence enhancement between hard and soft magnetic phase. In addition, nanocomposite permanent materials reduce the content of rare earth element and relatively inexpensive, owning a good prospect for development and act as the permanent functional device which are widely used in many high-tech industries such as computer, power source, aerospace, medical equipmen, etc. can also be prepared as magnetic recording medium and other magnetic devices. Although researchers have gained some high-performance Nanocomposite magnets, there is a very large gap with its theoretical value compared 120 MGOe. This is because the rapid decrease of coercivity while remanence enhanced, coercivity, thus limiting the improvement of energy product. Due to exchange coupling occurs primarily at the interface between the hard and soft phase, this paper introduces a way inserting non-magnetic phase between the hard and soft phase to study the influence of interface structure on properties of nanocomposite permanent magnetic materials.Hard/soft exchange-coupled SmCo/Fe bilayers with different thickness of soft magnetic layer were deposited on MgO(110) substrates by dc magnetron sputtering. The nucleation field of soft magnetic layer varies with the thickness of soft magnetic layer ranging from 6 nm to 40 nm was obtained by analyzing the magnetic hysteresis loops measured by SQUID-VSM at 25 K and 300 K. A critical improved equation was used to fit the relationship between the soft magnetic nucleation field and thickness and an ideal result was acquired. In order to study the influence of interface structure on magnetic properties of SmCo/Fe bilayers and exchange coupling, this paper introduces a non-magnetic interface layer between the hard and soft phase. The micro-magnetic theory was performed to fit the relationship between the soft magnetic nucleation field and thickness in various interface structure, giving the corresponding interface coupling constant. Compared experimental results with theoretical analysis, hard-soft magnetic exchange coupling weakened, the interface coupling constant and nucleation field decreased while irreversible field of hard magnetic phase increased with the inserting and increase of interface layer.