Procedure for the production of particles in which the particles have a SAR value (specific absorption rate) of between 10 and 40 W per g of Fe for a magnetic field intensity of 4 kA / m and an alternating magnetic field frequency of 100 kHz comprising the following steps: A1) preparation of a composition of at least one compound containing iron A in at least one organic solvent DV1, B1) heating the composition for at least 10 minutes until reaching a temperature in the range from 50 ° C to a temperature 50 ° C below the actual reaction temperature according to step C1 of the iron-containing compound A, C1) heating the composition to a temperature between 200 ° C and 400 ° C, the duration being of the heating phase for at least 30 minutes, D1) purification of the particles obtained by extraction with Soxhlet for a period of between 1 and 8 hours, E1) suspension of the nanoparticles purified in water or in an aqueous solution of an acid, F1) addition of a surfactant compound to the aqueous suspension obtained according to step E1, H1) purification of the aqueous dispersion obtained from the particles, I1) production of a dispersion of the particles according to step H1 in a mixture of water solvents and a water miscible solvent, J1) addition of an alkoxysilane to the dispersion of the particles in the solvent mixture obtained according to step I1, K1) particle purification .Procedimiento para la producción de partículas en el que las partículas presentan un valor SAR (tasa de absorción específica) de entre 10 y 40 W por cada g de Fe para una intensidad del campo magnético de 4 kA/m y una frecuencia del campo magnético alterno de 100 kHz que comprende los siguientes pasos: A1) preparación de una composición de al menos un compuesto que contiene hierro A en al menos un disolvente orgánico DV1, B1) calentamiento de la composición durante al menos 10 minutos hasta alcanzar una temperatura en el intervalo desde 50 °C hasta una temperatura 50 °C por debajo de la temperatur
