Dynamics of particles with cubic magnetic anisotropy in a viscous liquid

•Specific absorption rate of nanoparticles with cubic anisotropy in viscous liquid is calculated.•The viscous and magnetic magnetization reversal modes of particles are obtained.•Heating ability of iron nanoparticles is much higher than that of uniaxial ones.•The range of applicability of linear response theory is investigated. We calculated the specific absorption rate (SAR) and relaxation time of a dilute assembly of spherical iron nanoparticles with cubic anisotropy distributed in a viscous liquid. The behavior of unit magnetization vector was investigated by the solution of stochastic Landau–Lifshitz equation. The spatial orientation of magnetic nanoparticle was determined by the set of stochastic equations for multiple particle directors. The particle viscous and magnetic magnetization reversal modes are revealed at low and sufficiently high amplitudes of alternating magnetic field, respectively. The SAR of iron nanoparticle assembly is shown to exceed significantly that of iron oxide nanoparticles with uniaxial anisotropy at the same amplitudes and frequencies of applied magnetic field. The linear response theory is shown to be valid only at small magnetic field amplitudes, H0 ≤ 50–70 Oe.