Mossbauer studies on the spiral antiferromagnetic coupling in iron oxychloride

Fe-57 Mossbauer spectroscopy has been used to study the noncolinear spiral antiferromagnetic coupling in FeOCl. The paramagnetic to antiferromagnetic transition occurs at 85 +/- 1 K. Our Mossbauer studies confirm that the preferential orientations of the spin of Fe3+ which are crystallographically of equivalent sites are parallel to the b and C axes with varied timescale of spin-spin relaxation as a result of competition among the intralayer antiferromagnetic superexchange coupling. ferromagnetic direct exchange coupling, and mixed interlayer dipolar-dipolar interaction. (C) 2002 Elsevier Science B.V. All rights reserved.