Magnetic and hyperthermia properties of Ni1−xCux nanoparticles coated with oleic acid and silica prepared via sol–gel method

We report the magnetic and magnetothermal properties of functionalized Ni 1− x Cu x nanoparticles prepared by the sol–gel method, with x = 0.20–0.28 and having a size less than 10 nm. Zero-field-cooled thermal demagnetization measurements show that the Curie temperature can be brought into therapeutic range (315–320 K) by Cu substitution in Ni 1− x Cu x alloys. An aqueous suspension of selected composition Ni 0.73 Cu 0.27 milled for 30, 60, 80, and 120 min was made using acrypol 934 polymers. NPs milled for 120 min remained suspended for 10 h. The specific loss power (SLP) generated by magnetic nanoparticles was found to be 1.6 W/g for x = 0.20 and 0.6 W/g for x = 0.28. The SLP values of functionalized Ni 0.73 Cu 0.27 NPs for powder, as well as aqueous suspensions, show a quadratic dependence at a magnetic field up to 180 Oe at a fixed frequency of 425 kHz, respectively. The obtained SLP values for fluid Ni 0.73 Cu 0.27 NPs lie in the range of 12–25 W/g. The linear response theory was used to calculate the effective anisotropy constant of Ni 1− x Cu x ( x = 0.20 to 0.28) NPs coated with oleic acid and is found to lie within the range 2–3 × 10 4 J/m 3 .