EPR Study of the Single-Ion Magnetic Anisotropy of the Fe3+ Ion in a Diamagnetic PbGaBO4 Crystal

Crystals of a diamagnetic PbGaBO4 analog containing a small amount (about 0.5 at %) of Fe3+ ions are grown. The single-ion EPR spectra of Fe3+ in PbGa1 – xFexBO4 single crystals are analyzed with allowance for a crystal structure. The existence of four magnetically nonequivalent positions of Fe3+ ions with different local anisotropy axis directions has been confirmed. The parameters of the spin Hamiltonian written in the approximation of the local orthorhombic symmetry of a paramagnetic center are determined. The values of single-ion anisotropy constants, which are unusually high for S ions, is shown to be caused by a strong distortion of the ligand environment of Fe3+ ions. The single-ion contribution to the energy of the total magnetic anisotropy of a magnetically concentrated PbGaBO4 crystal is estimated. Two-ion mechanisms of the Fe–Fe interaction anisotropy are assumed to play a dominant role in the formation of magnetic anisotropy in a magnetically concentrated crystal.