Clarification of Coercive Mechanism in Rare Earth Iron Nitride Sm-Fe-N magnet

为了阐明间隙N原子在微观尺度上对R2Fe&lt；17&gt；N_3中基磁性的作用，我们用三方晶系Y_2Fe^&lt；17&gt；Y_2Fe_&lt；17&gt；3.1&gt；和单晶Nd2Fe_&lt；17&gt；17&gt；N_3。将所得结果与能带结构计算结果进行了比较。为了阐明Sm_2Fe_&lt；17&gt；N_3的矫顽力机制，我们还考察了Sm_2Fe_&lt；17&gt；N_3单晶粉末的颗粒(粉末)大小和表面清洗对矫顽场μ_0H_c的影响。结果表明，μ_0H_c随颗粒尺寸的增大而单调减小，表明其矫顽力机制为成核型。表面清洗前，当Sm_2F_&lt；17&Gt；N_3粉末表面有多个成核位时，μ_0H_c的值较小，表现出较强的温度依赖性，而表面清洗使μ_0H_c的温度依赖性较弱。在这项工作中，我们得到了合成的最大能量积(BJH)_&lt；max&gt；=330kJ/m~3，这是我们所知的最高值。

For clarifying the role that the interstitial N atoms played on the microscopic scale for basic magnetism in R_2Fe_<17>N_3, we determined the enhancements of Fe magnetic moments on the crystallographically different atomic sites and crystalline electric field parameter A_2^0 upon nitrogenation by neutron diffraction studies of the rhombohedral Y_2Fe^<17> and Y_2Fe_<17>N_<3.1> and high-field magnetization measurements of single crystalline Nd_2Fe_<17> and Nd_2Fe_<17>N_3, respectively. The results obtained are compared with those estimated by the band structure calculation. For clarifying the coercivity mechanism in Sm_2Fe_<17>N_3, we also examined the particle (powder) size and surface cleaning effects on the coercive field μ_0H_c for the Sm_2Fe_<17>N_3 single crystal powder. The results indicate that μ_0H_c monotonically decreases with increasing the particle size, suggesting that the coercivity mechanism is of a nucleation type. When there are many nucleation sites on the surface of Sm_2F_<17>N_3 powder before surface cleaning, the value of μ_0H_c is relatively small and reveals strong temperature dependence, while μ_0H_c is strongly enhanced by surface cleaning, leading to relatively weak temperature dependence. In this work, we obtained the resultant maximum energu product (BJH)_<max> = 330 kJ/m3, which is the highest as far as we know.