FMR study of interlayer coupling in Fe/Cr superlattices: Temperature dependence

The ferromagnetic resonance in two Fe/Cr superlattices with a relatively large value of biquadratic coupling constant was studied in a temperature range from 400 K down to liquid helium temperature. Monocrystalline samples [Fe(30 (A) over circle)/Cr(10 (A) over circle)](10) and [Fe(20 (A) over circle)/Cr(11 (A) over circle)](8) were grown by means of the MBE technique on MgO [100] and Al2O3 [101] substrates, respectively. Measurements were performed in magnetic fields up to 10 kOe at frequencies ranging from 17 to 37 GHz under both transversal and longitudinal FMR excitation. Resonance spectra including the acoustic and the optical branches show significant temperature dependence. The interlayer coupling parameters were numerically calculated from the experimental spectra on the basis of the biquadratic coupling model. The data obtained for temperature dependence of both bilinear and biquadratic coupling constants were discussed in the framework of existing theories.