Definition of a magnetic susceptibility of conglomerates with magnetite particles. Particularities of defining single particle susceptibility

Abstract

Data of a magnetic susceptibility of ferro-and the ferrimagnetic particles of many technogenic, natural, special media are especially demanded for the solution of various tasks connected with purposeful magnetic impact on these particles. One of productive approaches to definition of a magnetic susceptibility χ of these particles consists in receiving experimental data of a susceptibility of disperse samples 〈χ〉 with a disperse phase of these particles.The paper expounds and analyses the results of experiments on defining (by Faraday method in a magnetic field with intensity H=90–730kA/m) the magnetic susceptibility 〈χ〉 of disperse samples (conglomerates) with a given volume ratio γ of magnetite particles (γ=0.0065–0.25). The corresponding families of concentration and field dependences are provided alongside with discussing the applicability of linear and exponential functions to describe these dependences.We consider the possibility of defining single particles susceptibility χ (with simultaneous obtaining field dependence of this susceptibility) by the commonly used relation χ=〈χ〉/γ both at relatively small (preferable for accuracy reasons) values γ – to γ=0.02…0.025, as well as at increased values γ – up to γ=0.25.The data χ are provided depending on H and correlating with known data at H<90kA/m; they are obtained at small values γ when with almost double distance between the neighbouring particles (in comparison with their proper dimensions) the mutual adverse (to determine valid data χ)magnetic impact of particles is practically excluded. The article also gives the data χ received at increased values γ with almost halved distance between the surfaces of the neighbouring particles.It is specified that in the studied (post-extreme) area of H both variants of obtained field dependencesχare functionally identical within the accuracy of a constant, and close to an exponential dependence χ∼1/H0.75. With the account for the defined here value of constant-multiplier (0.8), it provides the grounds for obtaining valid data χ, employing the results of measuring 〈χ〉 for conglomerates with not obligatory small values of γ.It is demonstrated that being obtained by data χ, the calculated field dependence of the particle matter magnetic susceptibility χm (for the case when the particles are traditionally likened to balls with the characteristic for them demagnetising factor equalling 1/3) complies with the anticipated inverse function χm∼1/H in the studied area H (where magnetization M expressed as M=χH reaches saturation M=Const).