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 fieldH(OK) of 545 kG. Good fit to the spectrum at 290 K is obtained withH _eff=475 kG, δ=0.37 mm/s, 1/2e ² qQ(1+η ²/3)=0.70mm/s, θ and ?=90°. The Brillouin function forS=5/2 poorly fits the experimental data of hyperfine magnetic fields. In the critical rangeH _eff can be described byH(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 thec axis. The direction of magnetization is nearly perpendicular toV _zz in 110] direction.