Depression of particle growth with calcination at low temperature and their heat generation property in AC magnetic field for the nano-sized magnetic Y₃Fe₅O₁₂–nSmFeO₃ powders prepared by bead-milling

Abstract

Nano-sized Y₃Fe₅O₁₂–nSmFeO₃ mixed powder (ca. 20 nm in particle size) was prepared by bead-milling using 0.05 mmφ beads for 10 h. For the SmFeO₃-free sample (n = 0), the heat generation ability in an AC magnetic field (370 kHz, 1.77 kA·m⁻¹) was 0.34 W·g⁻¹ for the bead-milled sample, and it was increased by a calcination at low temperature. The maximum ability of 0.46 W·g⁻¹ in an AC magnetic field (370 kHz, 1.77 kA·m⁻¹) was obtained for the Y₃Fe₅O₁₂ (n = 0) sample (36.8 nm in particle size) calcined at 700°C. The heat generation mechanism changed from superparamagnetic to ferrimagnetic due to particle growth at 700°C for the n = 0 sample, because the heat generation ability (W·g⁻¹) depended on the cube of the magnetic field. A mixed SmFeO₃ phase acted as an impurity for depression of the particle growth for the Y₃Fe₅O₁₂ particles. The heat generation ability was slightly improved by the addition of SmFeO₃ and the maximum value was 0.48 W·g⁻¹ in an AC magnetic field (370 kHz, 1.77 kA·m⁻¹) for n = 0.2 and 0.4 samples. The maximum heat generation ability was decreased for the excessive SmFeO₃ mixed sample (n = 0.6). The calcination temperature for the formation of the ferrimagnetic material was increased by the SmFeO₃ addition due to the depression of particle growth.