Depression of particle growth with calcination at low temperature and their heat generation property in AC magnetic field for the nano-sized magnetic Y<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>–<i>n</i>SmFeO<sub>3</sub> powders prepared by bead-milling

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.