[en] Hysteresis loops of melt-spun Nd₁₃Fe₇₇B₁₀ were measured at different temperatures between 4.2 K and 250 K. The loops were analysed on the basis of the micromagnetism using the finite element technique. By fitting the calculated _iH_c with the experiment, the value of the exchange constant across the inter-grain boundary was estimated to be about 90% of that across the inner-grain boundary. _iH_c increases to a maximum at the spin reorientation temperature T_s and then decreases with increasing temperature. With decrease of the exchange interaction across the grain boundary, _iH_c decreases below T_s and increases above T_s, and the Stoner-Wohlfarth model provides the theoretical lower and upper limits of _iH_c below and above T_s, respectively. The calculations reproduce the hysteresis loops fairly well. The magnetization proceeds by non-coherent rotation, and the spin distribution becomes quite non-uniform in some grains when H decreases to near _iH_c. (author)