Investigation On The Preparation And Magnetic Properties Of SmCo-based Rare Earth Permanent Magnets For High Temperature Applications

For permanent magnetic materials, the working temperature increases from room temperatuer to high temperatuer. This demands that the magnetic properties fluctuate slightly with increasing temperature as soon as possible. So, it is necessary to develop the permanent magnetic materials with excellent thermal stability. In order to meet the demands of high performance and high dependability for the micro-electronics systems and micro-mechanical systems, the permanent magnetic materials applied for micro-magnetic devices must be deposited directly on the parts used for providing magnetic field as films. With increased working temperature for the micro-magnetic devices in recent years and the hige temperature comes from the micro-machining technology unavoidably, the magnetic behavior at high temperatures for the permanent magnetic films is being paid more and more attentions. But the conventional permanent magnetic materials are difficult to meet the high temperature application demand. Since 1990s, the investigations about the permanent magnetic materials for high temperature applications become a fundamental aspect to take into account in magnetism and magnetic materials.SmCo based rare-earth permanent magnetic materials combingin large intrinsic magnetic properties with low temperature coefficient, are the most promising candidates for high temperature applications. In this paper, SmCo based bulk and film materials for high temperature applications are investigated using SEM, EDS, XRD, AFM, DSC and VSM. Firstly, the SmCo based permanent magnets have been prepared by powder metallurgy process. Effect of the preparing parameters and composition on the magnetic properties is investigated. Two kins of permanent magnets are successfully fabricated, which can work at 500℃. Applications of the SmCo based permanent magnets in the periodic permanent magnetic (PPM) focusing system with open magnetic rings are investigated. Analyzing the magneitc field distribution of the axial magnetized open magnetic rings, and the PPM focusing system with open magnetic rings are designed and fabricated. Secondly, the SmCo based films have been prepared by magnetron sputtering process.Effect of the sputtering parameters on the composition, microstructure, and magnetic properties are investigated, and the sputtering parameters mediated composition (SPMC) effect is discussed. Based on the investigation about the crystal dynamics and the effect of annealing process one the microstructure and magnetic properties of the deposited amorphous films, the TbCu7-type SmCo based films are successfully prepared. Subsequently, the influence of the film thickness, substrate heating temperature, underlayer materials and their thickness on the coercivity of the SmCo based films is investigated. The growth orientation and magnetic properties are improved effectively. Finally, the temperature dependence of magnetic properties for the SmCo based films from 25 to 300℃is investigated. Different magneitc circuit structures are designed for the SmCo based films, and the magneitc field distribution in the working gap is calculated. The results can provide important reference for the films applying in micro-magnetic devices.