Size induced large upward shift of magnetic transition temperatures in nanowires of rare-earth transition metal alloy GdxCo1−x(x = 0.4)

Abstract

It has been observed that in nanowires (diameter ∼ 100 nm) of a rare-earth (RE) transition metal (TM) alloy GdxCo1−x(x = 0.4) the magnetic transition temperatures like the magnetization compensation temperatures (Tcm) can be shifted upward by nearly 350 K compared to that of the bulk and be made as high as 850 K. The saturation magnetization (MS) remains high over the whole temperature range compared to that the bulk and at room temperature the enhancement in MS is 33%. This enhances the applicability of the RE-TM alloy to well above the room temperature. The magnetic experiments were carried out in the temperature range 80 K–1100 K on the alloy nanowires grown by electrochemical synthesis in the nanopores of Anodic Aluminium Oxide (AAO) templates. It has been established that the large shift in the Tcm is linked to qualitative change in the nature of the anisotropy energy EA on size reduction, in particular in the temperature derivative dEA/dT that reaches more or less temperature independent value in the nanowires.