In this paper a preparation method for high moment CoFe thin films with soft magnetic properties is reported. A full control of coercivity in a series of $20\text{-}\mathrm{nm}$ -thick CoFe films has been achieved without using seed layers, additives, or thermal annealing. The films were sputtered directly onto Si substrates and the coercivity was varied by changing the mean grain size in the sputtered films. The mean grain size was in turn controlled via the sputtering rate. A reduction in the coercivity has been observed from $120\mathrm{Oe}$ for samples with a mean grain size larger than $17\mathrm{nm}$ down to $12\mathrm{Oe}$ for a sample with a mean grain size of $7.2\mathrm{nm}$ . The results are in good agreement with the “random anisotropy model” relating the coercivity to the mean grain size in polycrystalline ferromagnetic films.

Magnetite (Fe₃O₄) is predicted to be half metallic at room temperature (RT) and it shows the highest Curie temperature among oxides. The use of Fe₃O₄ thin films is therefore promising for spintronic devices such as magnetic tunnel junctions (MTJs) and magnetoresistive sensors. The structural, magnetic and magnetotransport properties of magnetite are reported to be strongly dependent on the growth conditions. We have developed a very simple deposition chamber for growing thin magnetite films via a chemical vapour deposition (CVD) process based on the Fe₃(CO)₁₂ carbonyl precursor. The structural, morphological, and magnetic properties of the as deposited Fe₃O₄ films have been investigated by means of time of flight secondary ion mass spectrometry, grazing incidence x-ray diffraction, x-ray reflectivity, atomic force microscopy, conversion electron Mössbauer spectroscopy and superconducting quantum interference device magnetometry. Magnetotransport measurements show magnetoresistance up to −2.4% at RT at the maximum applied field of 1.1 T. Resistivity measurements in the 100–300 K temperature range reveal that the magnetotransport properties of the Fe₃O₄ films are governed by inter-granular tunnelling of the spin-polarized electrons. The spin polarization is estimated to be around −16%. A possible route for increasing the spin-polarized performances of our magnetite films is proposed. We have also deposited Fe₃O₄/MgO/Co stacks by using a combined CVD and atomic layer-deposition process. The trilayer's hysteresis curve evidences the presence of two distinct switching fields making it promising for magnetite-based MTJ applications.