Electron magnetic resonance of iron-gallium borate single crystals

Electron magnetic resonance (EMR) studies of iron-gallium borate, FexGa1-xBO3, single crystals have been carried out in the frequency range ca. 8-38 GHz in magnetizing fields up to 10 kOe and the temperature range of 4-310 K. With decreasing x in the range of 0: 34 x 1, the EMR spectra show a gradual passage from a low-frequency antiferromagnetic resonance (AFMR) mode at x = 1 toward a coexistence of AFMR and cluster magnetic resonance arising, respectively, from completely and partially magnetically ordered crystal regions. Temperature and concentration dependences of magnetic characteristics of iron-gallium borates, namely, the Neel temperature, the Dzyaloshinskii-Moriya field, and the isotropic energy gap, have been determined by means of AFMR. In contrast to unmixed FeBO3, FexGa1-xBO3 crystals with 0: 34 x 0: 85 show anomalous nonmonotonic temperature dependences of the Dzyaloshinskii-Moriya field with a maximum well below the Neel temperature suggesting the occurrence of another magnetic transition in this temperature range. Published under license by AIP Publishing.