Low temperature magnetization and the law of approach to ferromagnetic saturation is investigated for sputtered amorphous films of composition F80−xNixB20 in the temperature range between 10 and 240 K, and in magnetic fields up to 4 T. The spontaneous magnetization, Ms, follows Bloch's T3/2−law and the high‐field magnetization obeys an l/H1/2−law indicating the presence of small elastic stress sources of diameters <4 nm. Annealing effects of ‐Ms and the spin‐wave stiffness constant are attributed to an increase of the magnetic exchange coupling.

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The specific heat of magnetite (Fe3O4) is measured from 5 to 130 K for two single crystals and near the Verwey transition temperature Tv (110 K ≤ T ≦ 130 K) for various polycrystalline samples. The data are compared to the large number of previous measurements. It is observed that the presence of vacancies in undoped Fe3O4 plays a dominant role in lowering and broadening Tv and diminishing ΔH. One of the single crystals has an entropy change of 6.24 J/K mol at Tv = 123.6 K (ΔH = 770 J/mol), which ie among the highest values observed up to date. It is concluded furthermore that in pure magnetite there exists only one anomaly in the low temperature specific heat Cp (1.5 K ≦ T ≦ 300 K) : the Verwey transition at Tv = 124 K, which is displayed by a single peak in Cp. This result is in contrast to numerous earlier measurements.

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