Quantum jumps in the magnetization of a magnet with antiferromagnetic impurities - art. no. 184415

The differential magnetic susceptibility of GdxY3-xFe5O12 (0.01 < x < 0.2) polycrystalline compounds is studied in the temperature range 0.6 to 4.2 K and in pulsed magnetic fields up to 50 T. The magnetization of the compound with the lowest Gd content (x = 0.01) shows instead of a classical, a quan tum (stepwise) phase transition to a completely saturated ferromagnetic pha se at T = 0.6 K, in magnetic fields around 33 T. To explain these results, a Heisenberg ferrimagnetic model with weakly coupled antiferromagnetic impu rities is used. Following this model, the nonequidistance of the energy lev els of the impurity ions causes the occurrence of susceptibility oscillatio ns under a variation of external magnetic fields.