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

3d过渡金属合金的磁化强度的成分依赖性很好地描述与Slater Pauling曲线。价电子数在刚性带模型解释这一行为中起着至关重要的作用，并且在Fe和Co之间的bcc合金中达到最高值。例如，减少原子间距离。因此，在电子数为26附近出现高磁化材料并且具有比环境压力下更大的晶格常数是合理的。获得更大原子间距的直接途径是利用外延生长技术。但是，相反，本项目引入间隙原子，如氮或碳，到体心立方矩阵与希望产生块体材料。我们采用的方法在以下句子中描述：将Fe-N或Fe-C的高温相淬火至室温，并冷却至4。2K的Fe-N合金，通过马氏体相变转变为具有铁磁性的bet结构。六点。%N时，bet相的体积分数增加到91%，并获得了215 emu/g的自发磁化强度。120 ℃热处理使其部分转变为α”相，但未观察到巨磁化。Fe-C系也发生了磁场诱发马氏体相变，但磁化强度比Fe-N系小。以Mn替代Fe，改变3d电子数为目的，在Fe-N合金中未能产生单一的γ相。

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.