Investigations of the growth and the saturation magnetization of garnet single crystals Y3Fe5xGaxO12 and Y3Fe5xAlxO12

Abstract

Mixed garnets of the composition Y3Fe5xGaxO12 (x = 0, 0.58, 0.91, 1.26, 2.20, 3.07) and Y3Fe5xAlxO12 (x = 0, 0.57, 1.00, 1.92, 3.20) were grown from the flux melt with application of the “induced striation method” (ISM). Growth conditions, nucleation temperatures, solubility curves, and values of the molar heat of solution are given. Some data about flux grown Gd3Ga5O12 are added. The magnetization was measured and theoretically calculated from 4.2 K up to the Curie temperature. The site occupation of Ga3+ and Al3+ has been determined according to the models of Néel, Dionne, and Gilleo. Compensation and Curie points were calculated and compared with experimental results.

Application of Ion‐Doped Y3Fe5O12 Nanoparticles for Self‐Controlled Magnetic Hyperthermia

“…The points represent experimental data from other studies. [18,26,27,30] characteristics of the MNPs so that they become suitable for use in SCMH. The so-called "size and surface" effects change the values of the exchange interactions, the magnetocrystalline anisotropy, and the lattice constants of the surface relative to the volume.…”

“…In both cases, this reduces the Curie temperature compared with the undoped sample because the number of magnetic interactions per formula unit decreases. [ 26,27,30,31 ] The sites preferentially occupied by the nonmagnetic ions depend on their size in relation to the Fe 3+ ion (0.75 Å), as Al 3+ (0.50 Å) and Ga 3+ (0.62 Å), which have a smaller radius compared with the iron ion, preferentially occupy the tetrahedral places, while Sc 3+ (0.81 Å) and In 3+ (0.82 Å), which have a larger radius compared with the iron ion, occupy octahedral places. It was experimentally shown [ 32 ] that this was true for small concentrations of nonmagnetic ions x (e.g., for Al 3+ ions at they replace Fe 3+ ions only in tetrahedral sites, while for some of the aluminiumions occupy octahedral sites [ 19 ] as well as for Ga 3+ [ 33 ] ).…”

“…Dependence of the phase-transition temperature T C of bulk samples on the degree of doping x (x ¼ y þ z) for: 1) M ¼ Al; 2) M ¼ Ga; 3) M ¼ In; and 4) M ¼ Sc. The points represent experimental data from other studies [18,26,27,30].…”

Study of the mass transport during crystal growth from high-temperature solutions by the “high-resolution induced striation method”

“…Using A , = 2 pm/h K, c, = 0.92 g/cm3, Ub = 14 kcal/mol [4], p = 5.30 g/cm3, and T = 1280 K one gets D/G,nn = 6.1 x loe6 cmls in good agreement with the magnitudes D/G,E which were determined by "dissolution striations" [6] and preparation of LPE garnet films with non-rotating substrates.…”

“…is constant, the time dependence of dc,-ac d T --> -= const. dt aT dt (4) Neglecting the time dependences of Fn, Geffn, and V , the solution of (3) is…”