Magnetic properties of monodispersed submicromic α-Fe2O3 particles

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Abstract
Magnetic properties are reported of recently prepared spherical hematite (α‐Fe2O3) particles of narrow size distributions with average diameters (d) varying between 20 and 300 nm. Mass magnetization (σ) of these particles has been determined as a function of temperature (T) up to 1000 K and of magnetic field (H) as high as 22 kOe. Specifically, magnetic behavior of α‐Fe2O3 particles of d = 300 nm is described in detail. Their Curie (Néel) temperature has been determined to be 960 K. The Bean‐Livingston plot indicates a change in magnetic anisotropy from higher symmetry at room temperatures to unidirectional behavior at elevated temperatures. This observation is consistent with the change of saturation and remanent magnetization with T. The measurements of σ on different size particles indicate that below 100 nm the particle magnetic susceptibility increases with decreasing size.

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