The recent discovery of Spin-ice is a spectacular example of non-coplanar spin arrangements that can arise in the pyrochlore A2B2O7 structure. We present magnetic and thermodynamic studies on the metallic-ferromagnet pyrochlore Sm2Mo2O7. Our studies, carried out on oriented crystals, suggest that the Sm spins have an ordered spin-ice ground state below about T* = 15 K. The temperature- and field-evolution of the ordered spin-ice state are governed by an antiferromagnetic coupling between the Sm and Mo spins. We propose that as a consequence of a robust feature of this coupling, the tetrahedra aligned with the external field adopt a "1-in, 3-out" spin structure as opposed to "3-in, 1-out" in dipolar spin ices, as the field exceeds a critical value.
@article{arxiv.0706.4145,
title = {Ordered spin-ice state in the geometrically frustrated metallic-ferromagnet Sm2Mo2O7},
author = {Surjeet Singh and R. Suryanarayanan and R. Tackett and G. Lawes and A. K. Sood and P. Berthet and A. Revcolevschi},
journal= {arXiv preprint arXiv:0706.4145},
year = {2009}
}