Table 1.
Size, Structural Phase, and Magnetic Properties of the Nanoparticles 1
| f ≈ 10−4 Hz | T = 10 K, f ≈ 10−4 Hz | T = 300 K, f = 50 kHz | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Sample Name | TEM Particle Size d (nm) (σ) | Hydrodynamic Size Dh (nm) (σ) | Iron Oxide Majority Phase | TB (K) | μ0HC (mT) | μ0HK (mT) | Ms (Am2/kg) | Mr/Ms | μ0Hc (mT) | MS (Am2/kg) | Mr/Ms |
| γFe2O3-6nm | 6.3 (0.19) | 25.4 (0.27) | γ-Fe2O3 | ~70 | 7.5 | 55 | 0.16 | — | — | — | |
| γFe2O3-8nm | 7.6 (0.20) | 29.9 (0.23) | γ-Fe2O3 | ~90 | 11.0 | 42 | 59 | 0.20 | 0.9 | 26 | 0.05 |
| γFe2O3-12nm | 11.7 (0.16) | 58.4 (0.25) | γ-Fe2O3 | ~220 K | 25.5 | 57.3 | 65 | 0.30 | 5.5 | 32 | 0.28 |
| γFe2O3-14nm | 13.8 (0.18) | 96.8 (0.19) | γ-Fe2O3 | ~300 K | 25.1 | 54.7 | 79 | 0.29 | 10.6 | 32 | 0.45 |
| Fe3O4-14nm | 13.5 (0.19) | 160.7 (0.20) | Fe3O4/γ-Fe2O3 | >300 K | 39.0 | 84.1 | 71 | 0.31 | 10.0 | 32 | 0.26 |
| Fe3O4-35nm | 35 (0.20) | 88.1 (0.18) | Fe3O4 | >300 K | 27.7 | 57.9 | 80 | 0.29 | 15.8 | 77 | 0.72 |
| Fe3O4-350nm | 350 (0.24) | 2751 (0.45) | Fe3O4 | >>300 K | 24.1 | 90 | 0.17 | — | — | — | |
1 Particle size d and its polydispersity σ, hydrodynamic size in Z average Dh and its polydispersity σ, iron majority phase, blocking temperature Tb, coercive field Hc, anisotropy field Hk, saturation magnetization Ms, and remanence ratio Mr/Ms of the samples measured at 10 K at low frequency (estimated SQUID measuring time of a hysteresis cycle t ≈ 3600 s, therefore f ≈ 10−4 s) and at 300 K at high frequency (f = 52 kHz).