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INVESTIGATION OF THE METAL-TO-SEMIMETAL TRANSITION IN NiS BY Ni-MOSSBAUER SPECTROSCOPY

J. FINK, G. CZJZEK, H. SCHMIDT and K. RUEBENBAUER

Institut fiir Angewandte Kernphysik, Kernforschungszentrum Karlsruhe, GFR

J. M. D. COEY and R. BRUSETTI

Transitions de Phases, CNRS, Grenoble, France

Abstract.

 - Mossbauer spectroscopy with 61Ni has been employed to investigate vibrational, magnetic and electronic properties of hexagonal NiS in the semimetallic antiferromagnetic and in the metallic, Pauli-paramagnetic phase. Upon transition to the metallic state the recoilless fraction decreases significantly, corresponding to a change of the Debye-temperature by about 20 %. There is at most a small change of isomer shift at the transition. The relative decrease of the magnetic hyperfine field with temperature is proportional to T2, as expected for single-electron excitations in itinerant antiferromagnets. A decrease of the electric field gradient both with temperature and with increasing content of Ni-vacancies in the antiferromagnetic phase indicates changes of the electronic structure which may promote the transition to the metallic state.  


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