Search for a new bulk ferromagnet with controlling interatomic distance and valence electron number

用Slater-Pauling曲线很好地描述了三维过渡金属合金磁化强度的成分依赖关系。价电子数在解释硬带模型的这种行为中起着至关重要的作用，在Fe和Co之间的bcc合金中达到了最高值。通过高压实验也知道，三维bcc合金的磁化强度随着压力的增加而降低，即原子间距离的减小。因此，在电子数为26附近有可能出现高磁化材料，并且晶格常数比环境压力下大。实现更大原子间距离的直接途径是利用外延生长技术。但是，目前的项目是在bcc基体中引入氮或碳等间隙原子，以期生产出块状材料。下面的句子描述了我们采用的方法；Fe-N或Fe-C高温相淬火至室温，冷却至4℃。为了使其通过马氏体相变转变为具有铁磁性的bet组织，在Fe-N合金上施加35t的高磁场。6。在零磁场条件下，bet相的体积分数从160 emu/g提高到91%，自发磁化强度达到215 emu/g。120℃热处理使其部分转变为α”相，但未观察到强磁化现象。Fe-C体系也发生了马氏体相变，但磁化强度小于Fe-N体系。我们在Fe- n合金中用Mn代替Fe，目的是改变三维电子数，但未能产生单相γ。

Composition dependence of magnetization for the 3d transition metal alloys is well described with the Slater-Pauling curve. The valence electron number plays an essentially important role to explain this behavior with the rigid band model and the highest value is attained in bcc alloys between Fe and Co. It is also known through high pressure experiments that magnetization of 3d bcc alloys decreases with increasing pressure, i. e., decreasing interatomic distance. Therefore, it is plausible to appear a high magnetization material at vicinity of electron number of 26 and with a larger lattice constant than at ambient pressure. The straight way to access the larger interatomic distance is to utilize epitaxial growth technique. But, instead, present project introduces interstitial atoms, such as nitrogen or carbon, into bcc matrix with a hope to produce bulk material. The method we employed is described in following sentences ; the high temperature phase of fee Fe-N or Fe-C is quenched to room temperature, and cooled to 4. 2K in order to transform them into bet structure with ferroiagnetism via the Martensitic transformation, fith application of high magnetic field of 35 T on the Fe-N alloy with 9. 6 at. %N, volume fraction of the bet phase increased to 91 % and attained spontaneous magnetization of 215 emu/g from 160 emu/g for zero magnetic field. Heat treatment at 120C partially transforms it into α" phase, but no indication of giant magnetization was observed. The magnetic field induced Martensitic transformation also took place in the Fe-C system, but resulted in smaller magnetization than Fe-N system. We substituted Mn for Fe in Fe-N alloy with aim of changing 3d electron number, but failed to produce single phase of γ.