Near-zero moment ferromagnetism in the semiconductor SmN
Journal Article

Published: Thursday, November 06, 2008
Journal: Physical Review B, Volume 78, Number 17, Pages 174406

Authors (1 total): A. Preston

Abstract: The magnetic behavior of SmN has been investigated in stoichiometric polycrystalline films. All samples show ferromagnetic order with Curie temperature (TC) of 27±3 K, evidenced by the occurrence of hysteresis below TC. The ferromagnetic state is characterized by a very small moment and a large coercive field, exceeding even the maximum applied field of 6 T below about 15 K. The residual magnetization at 2 K, measured after cooling in the maximum field, is 0.035µB per Sm. Such a remarkably small moment results from a near cancellation of the spin and orbital contributions for Sm+3 in SmN. Coupling to an applied field is therefore weak, explaining the huge coercive field. The susceptibility in the paramagnetic phase shows temperature-independent Van Vleck and Curie-Weiss contributions. The Van Vleck contribution is in quantitative agreement with the field-induced admixture of the J=(7/2) excited state and the (5/2) ground state. The Curie-Weiss contribution returns a Curie temperature that agrees with the onset of ferromagnetic hysteresis, and a conventional paramagnetic moment with an effective moment of 0.4µB per Sm ion, in agreement with expectations for the crystal-field modified effective moment on the Sm+3 ions.