X-ray photoelectron spectroscopy study of sputter-annealed Ni2.1Mn0.9Ga surface

The modifications in surface composition of Ni_2.1Mn_0.9Ga ferromagnetic shape memory alloy have been investigated using X-ray photoelectron spectroscopy (XPS) under various sputtering and annealing conditions. XPS core-level spectra show that sputtering makes the surface Ni rich. However, by annealing, the Mn content at the surface increases and at about 390 °C the bulk composition is restored. The valence band spectra show evidence of Ni related extra states for the sputtered surface, which decrease with annealing. This behavior is in agreement with the change in surface composition derived from the core-level spectra.