High temperature axial ratios c/a in hcp-based #x03B5;-type interstitial nitrides MNy with <F>M=Mn</F>, Fe, Ni

Axial ratios c/a of a series of manganese, iron and nickel nitrides MNy (<F>0.33<y<0.50</F>) with an hcp arrangement of M and with N in octahedral interstices, exhibiting #x03B5;-type ordering at room temperature in hexagonal superlattices with <F>a#x03B5;=31/2ahcp</F> and <F>c#x03B5;=chcp</F>, were analysed as a function of temperature and N content. c/a ratios are mainly affected by changes in the overall N content as well as by the temperature-dependent evolution of the magnetic ordering of the transition metals. However, ordering–disordering processes of N do not significantly affect the c/a ratios in the investigated materials. [Copyright &y& Elsevier]