Abstract: In this paper we study doped yttrium garnet (YIG) nanoparticles Y_3 [Fe_(2-y) M_y ]_a (Fe_(3-z) M_z )_d O_12, (M= Al, Ga, Sc are nonmagnetic ions), appropriate for Self-Controlled Magnetic Hyperthermia (SCMH) for in vivo and in vitro applications. A microscopic model (modified Heisenberg Hamiltonian) is presented, describing the super-exchange magnetic interactions in the tetrahedral and octahedral sublattices and between them. A methodology is proposed for determining the inter-sublattice and intra-sublattice exchange constants for different degrees of doping as well as the constants of single-ion magnetic anisotropy in dependence of temperature, concentration of doped magnetic ions and size of the magnetic nanoparticle (MNP). Using the Green's functions method, for the mixed yttrium garnet nanoparticles, the dependence of SAR coefficient on the amplitude and the frequency of the alternating magnetic dield, the temperature, and the magnetic inter-exchange interaction are studied. The calculations are made for monodisperse, non-interacting single-domain, heterogeneous spherical MNPs of the core/shell type.

Keywords: Y_3 Fe_5 O_12 nanoparticles; Magnetic properties; Ion doping; Green's function theory

| DOI: 10.17148/IARJSET.2022.9219