Raman Analysis Of AlxGa1-xN Films

Raman analysis of the E2 mode of AlxGal-xN in the composition range 0 ≤ x ≤ 1 is presented. The lineshape was observed to exhibit a significant asymmetry and broadening toward the high energy range. The spatial correlation model is discussed, and is shown to account for the lineshape. The model calculations also indicate the lack of a long-range order in the CVD (chemical vapor deposition) alloys. These results were confirmed by X-ray scattering: the relative intensity of the superlattice line was found to be negligible. The line broadening of the E2 mode was found to exhibit a maximum at a composition x∼0.5 indicative of a random disordered alloy system. The stress state of the alloys was found to be tensile and was attributed to the difference in the thermal expansion coefficients of the SiC substrate and the film.

FERROMAGNETISM AND ORDER IN NICKEL MANGANESE ALLOYS

An investigation of ferromagnetism in nickel manganese alloys containing up to 40 atomic per cent manganese has been carried out. Twenty alloys within this composition range were subjected to heat treatments such that the atomic arrangement within the alloys varied from disorder to a high degree of long range order.The degree of order of Ni3Mn calculated from measured saturation magnetization using the atomic model of ferromagnetism was consistent with the value calculated from the ratio of measured integrated intensity of the (110) X-ray diffraction superlattice line to that of line (111).The relationship between saturation magnetization and concentration for the disordered alloys can be explained adequately by the existence of short range order. A value of 3.4 Bohr magnetons for the effective magnetic moment of manganese atoms in a nickel lattice was deduced.