Effect of hydrogen charging on the magnetic and magnetoelastic properties of amorphous ferromagnetic alloys

In this study, the effect of hydrogen absorption on the electrochemical, magnetic and magnetoelastic properties of amorphous Fe73.5M1Nb3Si13.5B9 (M=Cu,Pt,Ag,Pd,Mn) have been investigated. The samples produced by the melt spinning method were cut 4cm long and 0.25 cm width. Hydrogen was charged cathodically for 5-40 minutes with the cathodic current density of 10-60 mA using 0.5 M H2SO4 solution with 0.1 g/İt AS2O3 as a poison. The cyclic polarisation curves were obtained using BAS100B electrochemical system. In the electrochemical measurement three electrodes were used and the potential values were reed with respect to a Ag/AgCl reference electrode. The structure of samples that annealed 475, 525 and 575 °C for 1 hour was investigated using X-ray diffractometer (Rigaku-Radb) system and no charge in amorphous structure before and after hydrogenization was observed. The magnetization (M-H) curves were measured using LakeShore 480 Fluxmeter at ac (50Hz). The magnetic field dependence of Young's modulus (AE effect) was measured by the vibrating read method. The second mode was excited with a free length of 2 cm. The Young's modulus values are normalized to the saturation modulus value (Es). Experimental results reveal that the hydrogen atoms charged in the amorphous ferromagnetic alloys are in a very unstable state. It was found that hydrogenization changes the shape of M-H curves of Fe-based amorphous alloys, but with evolving of hydrogen, M-H curves regains previous shape gradually. In addition, it was also observed that the partial substitution of Pt, Mn, Ag, Pd for Cu in Fe73.5Cu1Nb3Si13.5B9 alloys has a great influence in the hydrogen absorption properties. As a result, it was concluded that hydrogen in amorphous ferromagnetic alloys changes their magnetic and magnetoelastic properties significantly.KEYWORDS : FINEMET, amorphous ferromagnetic alloys, nanocrystalline alloys, hydrogen charging, magnetic properties, magnetoelastic properties, Young's modulus. IV