Se discute el efecto que tiene el contenido de agua en las propiedades magnéticas y estructurales de la goethita. Se sintetizaron cuatro muestras, dos a partir de precursores Fe(II) y dos de Fe(III); se caracterizaron por difracción de rayos X, análisis termogravimétrico, método BET, espectroscopia Mössbauer y medidas de magnetización. Los resultados sugieren que las muestras preparadas a partir de Fe(II) exhiben mayor contenido de agua, son menos cristalinas y no presentan ordenamiento magnético a temperatura ambiente (TA), en contraste con las Fe(III); el exceso de contenido de agua decrece el campo de saturación y las muestras exhiben exchange bias a 10K.

We have studied the effect of water content on the magnetic and structural properties of goethite. For that purpose, four samples were prepared using two different hydrothermal methods, two of them is derived on the Fe(II) precursors and the other two from Fe(III) precursors. The samples were characterized by XRD, TGA, BET, Mössbauer spectrometry at RT, 77 and 4.2 K and ZFC/FC curves. The results suggest that the goethites from the Fe(II) precursors are less crystalline, have higher water contents and do not show magnetic ordered structure at RT in comparison to the goethites from the Fe(III) precursors. Our results suggest that both structural and adsorbed water contents decreases the magnetic hyperfine field at 4.2 K, and all samples exhibited exchange bias at 10K.