中文摘要：

利用不同的测量方法，研究了MnFeP1-xAsx（0．32〈x〈0．66）材料巡游电子变磁性转变附近一级相变与其他物理性质变化的关系．可以发现，材料的一级相变是一个温度滞后为10K，但持续发生在至少66K的一个很大的温度区间的结构相变．磁性相变与一级相变的温度点并不对应．晶格突变与居里温度和一级相变温度点并不一一对应，属于磁致伸缩的机制，来源于磁弹性耦合．实验指出，顺磁-铁磁转变是在一级相变的过程中，由于晶格的连续变化，导致了a-b面内最近邻Fe-Fe原子间的距离增大，而非观察到的晶格突变所引起。

英文摘要：

The resistance, magnetization and strain measurements have been carried out on MnFeP0.45 As0.55 compound. We found that, at variance with what is commonly believed, the critical temperature points for the first order transition, paramagnetismferromagnetism transition, and lattice anomaly are not identical. The first order transition goes on in a quite wide temperature range with a thermal hysteresis of about 10K. In the duration of the first order transition, the paramagnetism-ferromagnetism transition is observed, which indicates that they are not related to the lattice anomaly. Thus, we attribute it to the continuous change of the lattice parameters due to the structure transition based on our observation and Zach et al.＇ s work. On the other hand, the lattice anomaly occurs at lower temperature than that of the first order structural and magnetic transitions. We conclude that it is a magnetostrictive behavior associated with the magnetoelastic coupling below the Curie temperature.