Spin orbital reorientation transitions induced by magnetic field

Abstract

Here we report on a new effect similar to the spin reorientation transition (SRT) that takes place at two magnetic fields of BSORT1 and BSORT2. 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 BSORT. 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 λSˆLˆ, therefore we name it spin orbital reorientation transition (SORT). The value of BSORT1 depends on the crystal field model parameters and the number of ions N in a given cluster, whereas BSORT2 is controlled mostly by the magnitude of the spin–orbit coupling λ. The explanation of SORT is given in terms of the spin MS and orbital momentum ML contributions to the total magnetization M=MS+ML. 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 λ.