A comparative study of nanosized iron oxide particles; magnetite (Fe3O4), maghemite (γ-Fe2O3) and hematite (α-Fe2O3), using ferromagnetic resonance

Abstract We investigated intra/inter particle interactions in single domain size magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ) and hematite (α-Fe 2 O 3 ) iron oxide particles. The magnetic analyses were done using vibrating sample magnetometer and magnetic resonance measurements that were taken from 5 to 300 K and from 120 to 300 K, respectively. The magnetic resonance analyses were done for the iron oxides, frozen under 5000 G fields in glycerol matrix. By changing the temperature, a change in resonance field lines was observed at each Fe 3 O 4 , γ-Fe 2 O 3 and α-Fe 2 O 3 nanoparticles. However, the fits in resonant lines showed that Lande g values (spectroscopic splitting factor) stayed stable with temperature decrease. The thermal sensitivities that were determined from Lande g factors, revealed three dominant interactions on resonant lines namely; the exchange coupling in between Fe 2+ , Fe 3+ and O − ( g 1  = 3.01 ± 0.08), Fe 3+ centers (1.88 ± 0.03 ⩽  g 2  ⩽ 2.02 ± 0.03, depending on iron oxide states) and flip flop of O − ions in between ionic states of Fe 2+ –O −1 and Fe 3+ –O −2 (2.35 ± 0.06 ⩽  g 3  ⩽ 2.44 ± 0.06, depending on iron oxide states).