THE EFFECT OF THE CRYSTAL-FIELD ON MAGNETIZATION STEPS DUE TO EXCHANGE-COUPLED EU2-XEUXSE( OPEN AND CLOSED TRIPLETS IN PB1)

The values of the magnetic fields at which magnetization steps (MSs) o ccur due to exchange-coupled open and closed triplets of Eu2+ ions (S = 7/2) are calculated for a Pb1-xEuxSe single crystal, taking into acc ount the crystal-field (CF) interaction, which causes the isotropic se paration between two consecutive MSs, Delta B = Bl+1 - B-l(I = 1, 2,.. ., 6), where B-l is the value of the [th MS, that exists in the absenc e of the crystal field to become anisotropic with respect to the orien tation of the external magnetic field (B). The contribution of the sin gle-ion anisotropic CF by an exchange-coupled open tripler (OT) leads to an average separation, Delta B-av(OT-CF), 10% higher than Delta B w hen B \\ [100], and 5 and 8% lower than Delta B for B \\ [110] and B \ \ [111], respectively. As for the exchange-coupled closed tripler (CT) , it was estimated that Delta B-av(OT-CF), 10% higher than Delta B whe n B \\ [100], and 3.4 and 4.1% lower than Delta B when B \\ [110] and B \\ [111], respectively. Furthermore, the values of Delta B-l(OT-CF) and Delta B-l(CT-CF) were found to depend on 1(1 = 1,...,6 for OT, and I = 1,...,9 for CT), varying by up to about 40%.