Local magnetic moment and hyperfine field in hydrogenated iron and iron-vanadium alloy |
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Authors: | M E Elzain A A Yousif |
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Institution: | (1) Physics Department, College of Science, Sultan Qaboos University, P.O. Box 32486, Al-Khod, Sultanate of Oman |
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Abstract: | The local magnetic moment and hyperfine fieldB
hf at Fe and V sites in hydrogenated iron and iron-vanadium were calculated using the discrete variational method. The variations in andB
hf with H occupation of the octahedral (O) site were considered. It was found that when H occupies the O site neighbouring an Fe atom, both local moment and hyperfine field at this atom decrease linearly with increasing number of H atoms. The rate of decrease is larger for Fe in iron as compared to iron in vanadium. On the other hand, when H resides at an O site next neighbouring an Fe atom, whether in iron metal or in iron-vanadium, the Fe magnetic moment increases slowly, while the hyperfine field remains almost constant. The V moment in iron, which is negative (–0.83
B
), becomes less negative (–0.30
B) as H occupies the neighboring O sites, whereas slight changes occur (–0.88
B) when H is at the next neighbouring O site. The net effect of H on Fe in iron is to decrease the average magnetic moment at a rate of 1.2
B per H/Fe for low H content. On the other hand, the average Fe moment in an iron-vanadium alloy increases if H resides at O sites which are immediate neigbours of V and next neighbours of Fe. This may explain the development of a magnetic state on hydrogenation of Fe-V alloys, which is exhibited by the specific heat and susceptibility measurements. The changes in the isomer shift were found to agree with experimental trends. |
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