Synthesis of GdFeO3 nanoparticles via low-temperature reverse co-precipitation: the effect of strong agglomeration on the magnetic behavior

Abstract

Gadolinium orthoferrite (GdFeO 3 ) seems to have potential as a dual-modal contrast agent for magnetic resonance imaging (MRI), thus its preparation in the form of ultrafine superparamagnetic nanoparticles is currently of great interest. In this work, nanocrystalline GdFeO 3 was successfully synthesized by the heat treatment (750 C, 4 h) of gadolinium and iron(III) hydroxides reversely co-precipitated at low temperature (0 C). Initial and resulting powders were analyzed by EDX, SEM, PXRD, Mssbauer spectroscopy, vibration magnetometry, etc. Gadolinium orthoferrite was formed as isometric nanocrystals with an average size of 233 nm, which were strongly agglomerated into clusters of about 200 nm in diameter. It was shown that the individual GdFeO 3 nanocrystals are superparamagnetic, but in the cluster form, they exhibit a collective weak ferromagnetic behavior. After ultrasonic-assisted disintegration of GdFeO 3 to a colloidal solution form, these clusters remained stable due to their strong agglomeration and low zeta potential value of 1 mV. Thus, it is concluded that the further use of the synthesized GdFeO 3 nanoparticles as a basis of MRI contrast agents will be possible only after the suppression of their clustering.