Broadening of ferromagnetic resonance linewidth in

We studied electron spin resonance (ESR) in an ordered double perovskite Ba 2 FeMoO 6 with the Curie temperature T C = 340 K . The T-independent gyromagnetic factor at T > T C is estimated as g ∼ 2 , suggesting that Fe 3 + is probed in the paramagnetic resonance. Below T C , the resonance signal shifts to lower fields with broadening of the linewidth. The linewidth increases down to our lowest temperature. Using the two-magnon scattering relaxation mechanism quantitatively reproduces the temperature dependence of the linewidth.