Magnetic Properties Of Fe-based Alloys Research Articles

Magnetic properties and structure of (Fe100-xGex)0.95Ni0.05 alloys (x = 0, 5, 10, 15, 20)

In this paper structural and magnetic properties of Fe-based alloys (Fe100-xGex)0.95Ni0.05 (x = 0, 5, 10, 15, 20) were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), magnetic and 57Fe Mössbauer spectroscopy measurements. Also, Density Functional Theory (DFT) calculations were used to study preferred crystal structure for Fe–Ni alloys with different Ge concentration. The results indicate that the addition of less than 20% Ge leads to preferred formation of alloys with bcc-type structure. The XRD measurement shows that all the investigated compounds have a body-centred cubic structure and the lattice constant increases with an increase in Ge concentration in the alloy from 2.87092 A˙ (x = 0) to 2.88594 A˙ (x = 20). The investigation of magnetic properties of (Fe100-xGex)0.95Ni0.05 proved their ferromagnetic behaviour, but magnetic moment per atom decreases with an increase in Ge concentration in the alloy from 2.31 μB (x = 0) to 1.66 μB (x = 20). In a temperature of about 820 K structural transformation from body-centred to face-centred cubic structure was observed for all the alloys. The temperature of this transformation was constant and independent of Fe or Ge concentration in the alloy.

Magnetic properties of Fe-based alloys

The magnetic properties of fcc FexNi1−x and FexCo1−x alloys grown on Cu(100) were investigated in an element-specific fashion. The technique employed was linear dichroism in photoemission, which by varying the chirality can also determine the magnetization axis. We observed a different behavior for the two alloys at Fe concentrations above 60%. At this concentration the FexNi1−x alloy shows a strong reduction of the Fe dichroism associated with the invar instability. This is in contrast to the FexCo1−x alloy, where the Fe dichroism stays essentially constant across the concentration. Despite these differences both systems show a change of the easy axis at roughly the same electron count. For small Fe concentrations the easy axis is in-plane along the [011] direction. This changes into the [001] direction at Fe63Ni37, which is at 0.7 excess electrons per atom when compared with Fe. This is different to the bulk, where a change occurs at Fe25Ni75. We find the easy axis change for FexCo1−x to occur at 49% Fe. This would be equivalent to 0.5 excess electrons when compared with Fe.