Spin orbital reorientation transitions induced by magnetic field

Here we report on a new effect similar to the spin reorientation transition (SRT) that takes place at two magnetic fields of B-SORT1 and B-SORT2. The effect is observed in the magnetization curves of small Mn3+ magnetic clusters in the wurtzite GaN (being in a paramagnetic state) calculated using crystal field model approach. The obtained results suggest that the computed magnetic anisotropy (MA) reverses its sign on increasing B across B-SORT. However, a detailed analysis shows that MA is unchanged for high magnetic fields. We show that the observed effect arises from the interplay of the crystalline environment and the spin-orbit coupling lambda(S) over cap(L) over cap, therefore we name it spin orbital reorientation transition (SORT). The value of B-SORT1 depends on the crystal field model parameters and the number of ions.. in a given cluster, whereas B-SORT2 is controlled mostly by the magnitude of the spin-orbit coupling lambda. The explanation of SORT is given in terms of the spin M-S and orbital momentum M-L contributions to the total magnetization M = M-S + M-L.The similar effect should also be present in other materials with not completely quenched (non zero) orbital angular momentum L, a uniaxial magnetic anisotropy and the positive value of lambda.