The M(T) and M(H) curves were measured to study the spin-ordered state in MnF3 at low temperatures. In order to obtain the temperature dependence of magnetization, Mn3+ NMR resonance frequency was measured as a function of temperature. The resulting curve fits well to the initial temperature dependence of the magnetization expected for antiferromagnets with magnetic anisotropy, T(3/2)exp(-E-G/k(B)T), with an energy gap E-G of about 30 K. From the comparison of the M(H) curve and classical theory, the relation between the anisotropy energy, K-a, and the exchange coupling constant between the nearest neighbors, J(1), was found to be K-a similar to - 1.8J(1) + 9.8 in the absolute temperature unit. 0 2016 Elsevier B.V. All rights reserved.