Carboxylated magnetic nanoparticles as MRI contrast agents: Relaxation measurements at different field strengths

► Magnetic resonance relaxation measurements were done at different field strengths. ► Results show characteristic differences between the tested carboxylated MFs. ► r1 and r2 relaxivities depend on the thickness of the protecting layer. ► MFs have high r2/r1 ratios at each magnetic field.