In-situ Scanning Transmission Electron Microscopy Annealing Studies of Ni1-xCrx Nanocluster and Correlation with Magnetic Properties

Metallic nanostructures show unique physical and chemical properties compared to their bulk counterparts due to their high surface area to volume ratio. For instance, magnetic nanoclusters (NCs) show superparamagnetic behavior only when they are below a certain critical size [1]. In addition, intrinsic magnetic properties such as the Curie temperature (Tc), saturation magnetization (Ms), and coercivity are mainly determined by the crystal structure, stoichiometry, and morphology of the NCs. In particular, the Tc of Ni1-xCrx NCs drops sharply with increasing Cr concentration [2]. This feature is very attractive and provides a way to tune the Tc of Ni1-xCrx NCs between temperatures of 314 and 319 K. One important application of this special feature is localized hyperthermia [3]. Hyperthermia is a method used to treat a variety of tumors by increasing the temperature of the body. Cancer cells are more susceptible to high temperatures (314-319 K) than normal tissue cells, which can survive temperatures up to 333 K. Thus, magnetic NCs in an alternating magnetic field can be used to induce heating of specific regions of the body [2].