【摘要】 用磁测量和X射线衍射方法研究了R₁₅B₇Fe₇₈（R=MM,Pr,Nd,Sm,Gd,Y）和Nd₁₅B7(Fe_1-xM_x)₇₈（M=Co,Mn,Cr）的结构和内禀磁性。X射线衍射实验表明,这些化合物皆属四方结构。R₁₅B₇Fe₂₈的晶格常数随稀土原子序数的增加而减小,反映了镧系收缩的特点。居里温度随稀土金属原子序数的增加而增高,反映了稀土-铁原子间的间接交换作用的影响,Gd₁₅B₇Fe₇₈具有最高的居里温度。在Nd₁₅B₇(Fe_1-xM_z)₇₈中,以Co代Fe时,晶格常数随x的增加而减小;居里温度随x的增加而单调显著上升。以Mn代Fe时,晶格常数随x的增加而增大;居里温度则随x的增加而急剧下降。居里温度的变化,说明R₁₅B₇Fe₇₈的居里温度主要由3d过渡族原子间的直接交换作用所决定的。以Co代Fe,当x=0.2时,Nd₁₅B₇(Fe_1-xCo_x)₇₈的饱和磁化强度出现极值。更多还原

【Abstract】 The crystallographic structure and intrinsic magnetic properties of R₁₅ B₇ Fe₇₈（R=MM, Pr, Nd, Sm, Gd and Y） and Nd₁₅B₇(Fe_1-xM_x)₇₈（M=Co, Mn and Cr） have been studied by magnetic measurements and X-ray diffraction experiments. These compounds crystallize in a tetragonal structure. The Lanthanide contraction results in a decrease of lattice parameters with increasing atomic number of rare earth elements. The curie temperature T_c is found to be increased with increasing atomic number of R, and T_c of Gd₁₅B₇Fe₇₈ is the highest, which shows the effect of R-Fe exchange interaction. For the series of Nd₁₅B₇(Fe_1-xM_x)₇₈, curie temperature T_c increases significantly with the content of Co, whereas the substitution of Fe with Mn results in a sharp decrease of curie temperature. The sensitive effect of substitution of Fe with other 3d-transition metals on curie temperature indicates that the curie temperature of R₁₅B₇Fe₇₈ is essentialy determined by 3d-3d atoms exchange interaction. The variation of saturation magnetization of Nd₁₅B₇(Fe_1-xCo_x)₇₈ as a function of the content x of Co shows a maximum around x=0.2.更多还原