Magnetic moment of α″-Fe16N2 films (invited)

Abstract

In order to determine the value of the intrinsic magnetic moment of the α ″ phase, the films of nitrogen-martensite with various N content were fabricated under various reactive sputtering conditions. The magnetic moment of (α ″+α′)-Fe16N2 films is discussed in connection with the change of the unit-cell volume of the bct structure and the degree of N site ordering in nitrogen-martensite. As a result, it is found that (1) the same structure as bulk α ″-Fe16N2 is realized in the present films, (2) the saturation magnetization σs of the α′ phase increases about 4% with increasing unit-cell volume of the α′ phase, (3) the degree of N site ordering from α′ to α ″-Fe16N2 does not much affect σs, and (4) the experimentally obtained maximum value of σs for the (α ″+α′)-Fe16N2 film was 232 emu/g. The intrinsic value of σs in the α ″ phase (in the perfectly ordered state) is proposed to be no more than 240 emu/g at 300 K.