EPR and optical absorption studies on Gd3+ ions in ammonium hydrogen malonate single crystals

X-Band electron paramagnetic resonance (EPR) studies of Gd3+ ions in ammonium hydrogen malonate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of four physically equivalent but magnetically inequivalent sites. The zero-field splitting parameters and g factor are determined. The Gd3+ ion is in 8S state; its levels are split by the action of the crystalline electric field of monoclinic symmetry. The optical absorption spectra of Gd3+ ions in single crystals of ammonium hydrogen malonate are also recorded at room temperature. The energy levels of the 4f7 configuration are calculated and compared with those observed experimentally. The values of E1=5854±11, E2=31±0.36, E3=592±3.3 and ζ4f=1595±25 cm−1 are found to give the best over-all agreement between experimentally observed and calculated levels.