College Park, Maryland      June 6 - 10 , 2004

ACNS Home Meeting Announcement Committees and Contacts Registration Abstract Submission Travel Reimbursement Dates to Remember

T1-C2 (9:00 AM): Commensurate-Incommensurate Magnetic Phase Transition in Magnetoelectric Single Crystal LiNiPO₄

D. Vaknin, J. L. Zarestky (Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011)

Neutron scattering studies of single-crystal LiNiPO₄ reveal a spontaneous first-order commensurate-incommensurate magnetic phase transition. Short- and long-range incommensurate phases are intermediate between the high temperature paramagnetic and the low temperature antiferromagnetic phases. The modulated structure has a predominant antiferromagnetic component, giving rise to satellite peaks in the vicinity of the fundamental antiferromagnetic Bragg reflection, and a ferromagnetic component giving rise to peaks at small momentum-transfers around the origin at (0,± Q,0). The wavelength of the modulated magnetic structure varies continuously with temperature. It is argued that the incommensurate short- and long-range phases are due to spin-dimensionality crossover from a continuous to the discrete Ising state. These observations explain the anomalous first-order transition seen in the magnetoelectric effect of this system.

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