Mössbauer effect study of SrEu2Fe2O7

The antiferromagnetic ferrite SrEu₂Fe₂O₇ was studied by Mössbauer effect of⁵⁷Fe in the range 77 650 K. Analysis of the data gives a Neel temperature of 544 K±2 K and an extrapolated effective magnetic field H(OK) of 545 kG. Good fit to the spectrum at 290 K is obtained with H _eff=475 kG, δ=0.37 mm/s, 1/2 e ² qQ(1+ η ²/3)=0.70mm/s, θ and ϕ=90°. The Brillouin function for S=5/2 poorly fits the experimental data of hyperfine magnetic fields. In the critical range H _eff can be described by H(T)=H(0) D(1- T/T _N )^β, where β nearly 0.29. The quadrupole interaction parameter is quite temperature independent, of the order of 0.69 mm/s in the paramagnetic state. Agreement with the value obtained by a point charge calculation is good. The largest axis of the EFG tensor, V _zz , lies in the plane (110), making an angle of 22.6° with the c axis. The direction of magnetization is nearly perpendicular to V _zz in [110] direction.