Magnetic field effect on hemin

Abstract Magnetic behaviour of hemin has been investigated by means of magnetostatic methods, AC-susceptibility measurements and EPR spectroscopy. The measurements were made using polycrystalline and oriented samples of hemin in the temperature range 2.3–292 K and in magnetic fields up to 6 T. In the paramagnetic region, the susceptibility obeys the Curie–Weiss law with positive Curie–Weiss temperature. At low temperature, a rapid increase of the susceptibility is noticed but up to 2 K no long-range correlations are observed. The studies show that the iron ion in hemin exists in two spin states ( S= 5 2 and 1 2 ). The applied magnetic field increases the occupation of the low-spin state. Hemin shows high-field-induced magnetic anisotropy which, similar to the susceptibility, increases with decreasing temperature.