Structural, electrical and magnetic properties of (Fe1-xMnx)75P15C10 amorphous alloys

Abstract

(Fe1-xMnx)75P15C10 amorphous alloys ribbons have been prepared by conventional melt-spinning technique (rapid cooling) with different wheel speeds in an argon atmosphere. The microstructural analysis were done by X-ray diffraction technique, Scanning electron microscopy (SEM). Both the XRD and SEM confirm the samples the amorphous (glassy) structure of the as made samples. The elemental analysis of the samples was carried out using energy dispersive X-ray spectroscopy (EDS) which reveals the presence of Fe, Mn, P and C elements in the sample. The glass transition temperature (Tg ) , the crystallization temperatures (Tx) and the mass loss and/or gain of all the samples were investigated by differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA). The electrical resistivity (𝜌) of amorphous (Fe1-xMnx)75P15C10 alloy ribbons have been studied as a function of temperature between 77K to 600K. It has been observed that the resistivity increases slightly with increasing temperature upto room temperature then it is increasing rapidly for x=0 and 0.05. At larger x, 𝜌(𝑇)develops a minimum at room temperature which can have different slopes, 𝑑𝜌𝑑𝑇 which has been ascribed to a superposition of scattering from the structural topological disorder and the spin topological disorder. The magnetic field dependence of magneto-resistanceΔ𝜌(𝐻) normalized to the resistivity of the sample in zero magnetic field 𝜌0 have been studied. It is observed that an anomalous change of MR% around 0.3 tesla occurs. Both positive and negative magnetoresistance have been observed as a function of applied magnetic field. The magnetic hysteresis (M–H) loop of the as-made samples show high saturation magnetization (Ms). The value of saturation magnetization is found to decrease with increasing Mn. This is attributed to the magneto-elastic scattering. The coercivity increases gradually with increasing Mn content up to 30 at. % Mn content. The increase in coercivity seems to be related to the decrease in glass-forming ability with increasing Mn content. The variation of complex permeability (real and imaginary part respectively) as a function of frequency from 100Hz-120MHz show high effective permeability of 2.2×104 . The value of effective permeability is found to have decreased with increasing Mn contents .These anomalous magnetic properties lead to the suggestion that the antiferromagnetic interactions introduced by Mn atoms cause deviations from a pure ferromagnetic structure at low Mn concentrations. However at higher Mn contents a competing ferro and antiferromagnetic interaction might result in a frustrating system resulting in magnetic relaxation.