Nd-Fe-Co-B永磁合金的磁性和穆斯堡尔效应的研究

STUDIES OF MAGNETIC PROPERTIES AND MOSSBAUER SPECTROSCOPY OF Nd-Fe-Co-B PERMANENT MAGNETS

本文研究了Nd_(17)(Fe_(1-x)Co_x)_(75)B_8(x=0,0.05,0.1,0.2和0.3)永磁合金的磁性和穆斯堡尔谱。得到了合金中四方相、富B相和富Nd相的穆斯堡尔参数——同质异能位移、电四极分裂和超精细场随Co含量的变化关系;根据合金中各含铁物相及四方相中各铁晶位的穆斯堡尔亚谱面积定量估算了各物相的体积分数和铁、钴原子在四方相各晶位的分布情况;由四方相穆斯堡尔谱第2与第3条谱线的强度比计算了合金的磁矩取向角。并从上述穆斯堡尔谱中获得的微观结构方面的结果讨论了合金的剩磁、矫顽力和居里温度。

Magnetic properties and Mossbauer spectroscopy of Nd_(17)(Fe_(1-x) Co_x)_(75)B_8 (x=0, 0.05, 0.1, 0.2 and 0.3) alloys have been studied. The dependences of isomer shifts, quadrupole splits and hyperfine fields on Co concentration have been obtained. The results show that hyperfine fields on six iron sites decrease with increasing Co concentration, but the slopes are different. The slopes are biggest for the J_2 and c sites and smallest for e site. The distributions of Co and Fe atoms on six iron sites are calculated by the Mossbauer subspectral areas. Co atoms preferentially occupy the k_2 and J_2 sites and Fe atoms preferentially occupy the j_1 site and randomly the k_1 site. The e and c sites seem to be only occupied by Fe atoms. The preferential occupation of the k_2 and j_2 site for Co atoms is a cause of increasing Curie temperature. X-ray, metallographic and Mossbauer effect experiments show that there exists Nd(Fe, Co)_2 phase at Co concentration x≥0.1 and its amount is about 3%. It leads to a rapid decrease of coercivity. The volume percentages of every phases, the orientation angles and moments of Fe, Co and Nd atoms are calculated with the Mossbauer quantitative phase analysis, with the ratio of the second to the third line and with the relationship between the hyperfine field and moment of Fe atom respectively. Further, according to above results, the magnetization and remanence of alloys are estimated, which correspond with experimental results.