Determination of the Landau–Lifshitz damping parameter by means of complex susceptibility measurements

A new experimental method for the determination of the Landau–Lifshitz damping parameter, αα, based on measurements of the frequency and field dependence of the complex magnetic susceptibility, χ(ω,H)=χ′(ω,H)-iχ″(ω,H)χ(ω,H)=χ′(ω,H)-iχ″(ω,H), is proposed. The method centres on evaluating the ratio of fmax/fres, where fres is the resonance frequency and fmax is the maximum absorption frequency at resonance, of the sample susceptibility spectra, measured in strong polarizing fields. We have investigated three magnetic fluid samples, namely sample 1, sample 2 and sample 3. Sample 1 consisted of particles of Mn0.6Fe0.4Fe2O4 dispersed in kerosene, sample 2 consisted of magnetite particles dispersed in Isopar M and sample 3 was composed of particles of Mn0.66Zn0.34Fe2O4 dispersed in Isopar M  . The results obtained for the mean damping parameter of particles within the magnetic fluid samples are as follows: 〈α(Mn0.6Fe0.4Fe2O4)〉=0.057〈α(Mn0.6Fe0.4Fe2O4)〉=0.057 with the corresponding standard deviation SD=0.0104SD=0.0104; 〈α(Fe3O4)〉=0.1105〈α(Fe3O4)〉=0.1105 with the corresponding standard deviation, SD=0.034SD=0.034 and 〈α(Mn0.66Zn0.34Fe2O4)〉=0.096〈α(Mn0.66Zn0.34Fe2O4)〉=0.096 with the corresponding standard deviation, SD=0.037SD=0.037.