Ferromagnetism and strong magnetic anisotropy of the PbMnBO4 orthoborate single crystals

The PbMnBO4 orthoborate single crystals were first grown and their magnetic properties and ferromagnetic resonance were studied. It was found that the ferromagnetic state below the Curie temperature TC=31K is characterized by the strong magnetic anisotropy. The significant effective anisotropy fields of PbMnBO4 determine the energy gap in the FMR spectrum, which is extraordinary large for ferromagnets (112GHz at T=4.2K). It was shown that the static Jahn–Teller effect characteristic of the Mn3+ ion leads to both the ferromagnetic ordering and the strong magnetic anisotropy in the crystal. In the strong external magnetic field the induced ferromagnetic ordering is retained in the crystal above the Curie temperature up to the temperatures multiply higher than TC. A weak anomaly of the dielectric permittivity was observed in PbMnBO4 at the Curie temperature at which the long-range ferromagnetic order is established.