Size-dependent magnetic and magnetothermal properties of gadolinium silicide nanoparticles.

Gadolinium silicide (Gd 5 Si 4 ) nanoparticles are an interesting class of materials due to their high magnetization, low Curie temperature, low toxicity in biological environments and their multifunctional properties. We report the magnetic and magnetothermal properties of gadolinium silicide (Gd 5 Si 4 ) nanoparticles prepared by surfactant-assisted ball milling of arc melted bulk ingots of the compound. Using different milling times and speeds, a wide range of crystallite sizes (13-43 nm) could be produced and a reduction in Curie temperature ( T C ) from 340 K to 317 K was achieved, making these nanoparticles suitable for self-controlled magnetic hyperthermia applications. The magnetothermal effect was measured in applied AC magnetic fields of amplitude 164-239 Oe and frequencies 163-519 kHz. All particles showed magnetic heating with a strong dependence of the specific absorption rate (SAR) on the average crystallite size. The highest SAR of 3.7 W g -1 was measured for 43 nm sized nanoparticles of Gd 5 Si 4 . The high SAR and low T C , (within the therapeutic range for magnetothermal therapy) makes the Gd 5 Si 4 behave like self-regulating heat switches that would be suitable for self-controlled magnetic hyperthermia applications after biocompatibility and cytotoxicity tests.