Near-zero-moment ferromagnetism in the semiconductor SmN

Abstract

The magnetic behavior of SmN has been investigated in stoichiometric polycrystalline films. All samples show ferromagnetic order with Curie temperature ͑T C ͒ of 27Ϯ 3 K, evidenced by the occurrence of hysteresis below T C . 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 0.035 B 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 temperatureindependent 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 0.4 B per Sm ion, in agreement with expectations for the crystal-field modified effective moment on the Sm +3 ions.

Magnetic properties of ErN films

“…Using a parallel development of experimental and theoretical work, we have recently shown that GdN is a small gap semiconductor with potentially spin polarized carriers [3,4]. Subsequently, we have found that DyN and SmN are also ferromagnetic semiconductors in their ground states [5,6]. In the present paper we describe the magnetic properties of ErN films.…”

4f conduction in the magnetic semiconductor NdN

“…Experiment has shown the magnetisation of SmN is close to extinguished by this opposition. A value of 0.03 µ B per Sm 3+ ion is found that is furthermore dominated by the orbital contribution [30,31].…”

On the ferromagnetic ground state of SmN

“…In recent years, research into SmN has been driven by two main considerations; its potential for spintronic applications and its vanishingly small ferromagnetic moment. It is a member of the rare-earth nitride series, a group of materials owing their promise for spintronic applications to their status as intrinsic ferromagnetic semiconductors [1][2][3][4][5][6][7][8][9][10]. SmN is especially unique among the series, with a vanishingly small ordered moment arising from the near-cancellation of spin and orbital moments [4,5] fixed antiparallel by strong spin-orbit coupling.…”

“…It is a member of the rare-earth nitride series, a group of materials owing their promise for spintronic applications to their status as intrinsic ferromagnetic semiconductors [1][2][3][4][5][6][7][8][9][10]. SmN is especially unique among the series, with a vanishingly small ordered moment arising from the near-cancellation of spin and orbital moments [4,5] fixed antiparallel by strong spin-orbit coupling. So far the spintronic potential of the RENs remains largely untapped, though GdN has been integrated within spinfilters [11,12] and field effect transistors [13] while DyN has been incorporated into a magnetic tunnel junction [14].…”