Magnetic oscillations in β″-(BEDT-TTF) 4(NH 4)[Fe(C 2O 4) 3]·DMF: Fermi surface study and frequency mixing

The interlayer magnetoresistance of the quasi-2D organic superconductor β″-(ET) ₄(NH ₄)[Fe(C ₂O ₄) ₃]·DMF has been investigated in pulsed magnetic fields of up to 55 T. According to band structure calculations, the Fermi surface results from the hybridisation of elliptical tubes yielding two compensated electron and hole orbits. Actually, the Fourier spectrum of the oscillatory magnetoresistance exhibits various frequencies which can be regarded as linear combinations of the two frequencies with the highest amplitude (F _a=(48±2) T and F _b=(241±5) T) corresponding to 1.2% and 6.0% of the first Brillouin zone area, respectively. The oscillatory spectrum can be accounted for by three compensated electron and hole orbits and combination frequencies typical of coupled orbits networks.