High field Mossbauer spectroscopy provides a selective method of measurement of the magnetic susceptibility due to paramagnetic Mossbauer atoms, and is well adapted for isotropic ions. This method was successfully tested on crystalline KFeF4 above its Neel temperature. In the case of MnFeF5(H2O)2, a reversal of the susceptibility of the iron sublattice was observed near 145 K, and explained in agreement with previous data on the magnetic interactions.