Size induced large upward shift of magnetic transition temperatures in nanowires of rare-earth transition metal alloy Gd x Co1−x (x = 0.4)

Highlights: • Gd and Co make a ferrimagnetic alloy with a magnetic compensation temperature T_cm. • Gd_0.4Co_0.6 alloy nanowire of diameter 100 nm was prepared by electrochemical method. • In nanowire T_cmis nearly 350 K shifted upward. • Change in the nature of the anisotropy energy (E_A) in nanowire is the reason of the large shift. It has been observed that in nanowires (diameter $\sim$ 100 nm) of a rare-earth (RE) transition metal (TM) alloy Gd_xCo_1−x(x = 0.4) the magnetic transition temperatures like the magnetization compensation temperatures $\left(T_{cm}\right)$ 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 $\left(M_S\right)$ remains high over the whole temperature range compared to that the bulk and at room temperature the enhancement in $M_S$ 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 $T_{cm}$ is linked to qualitative change in the nature of the anisotropy energy $E_A$ on size reduction, in particular in the temperature derivative $d{E}_A/dT$ that reaches more or less temperature independent value in the nanowires.