Nd2(Fe1-xMnx)14B的低温内禀矫顽力

当x<0.5时,Nd₂(Fe_1-xMn_x)₁₄B可形成四方晶体结构,空间群为P4₂/mnm。在低温下,该赝三元化合物的大块铸态样品具有高矫顽力。此矫顽力不依赖于热处理等工艺过程,因此具有内禀性质。内禀矫顽力 _iH_c与样品的成分有关。Nd₂(Fe_1-xMn_x)₁₄B的起始磁化曲线具有传播场H_p,并且H_p的数值与 _iH_c接近。这表明内禀矫顽力是由畴壁钉扎造成的。研究了 _iH_c与温度的变化关系,并估算了钉扎位垒的强度。测量了Nd₂(Fe_1-xMn_x)₁₄B的居里温度和饱和磁化强度。在此赝三元化合物中,交换作用随Mn对Fe的替换而急剧降低。这使得畴壁厚度变窄。Nd₂(Fe_1-xMn_x)₁₄B的磁化和反磁化行为可用窄畴壁的特征来解释。 关键词：

INTRINSIC COERCIVITY AT LOW TEMPERATURES IN Nd2(Fe1-xMnx)14B

Nd₂(Fe_1-xMn_x)₁₄B crystallize in the tetragonal structure, space group P4₂/mnm, when x<0.5. A large coercive force has been observed at T = 1.5K in the as-cast bulk samples of the pseudoternary compounds. It does not depend on treatment such as milling, sintering and annealing. Accordingly, the coercive force must be intrinsic. The intrinsic coercive force _iH_c shows a composition dependence. The form of the virgin magnetization curve is characterized by a propagate field H_p. The value of H_p is close to that of _iH_c, indicating that the intrinsic coercive force is created by domain wall pinning. The temperature dependence of _iH_c were studied. The strength of the pinning potential barrier was estimated. The Curie temperature and saturation magnetization of Nd₂(Fe_1-xMn_x)₁₄B were measured. The exchange interaction in the pseudoternary compounds decreases dramatically with substitution of Mn for Fe. That results in a decrease of the thickness of domain walls. The magnetization and demagnetization behaviors in Nd₂(Fe_1-xMn_x)₁₄B can be understood in terms of narrow domain walls.