Proceedings of the International Conference on Magnetism

J. Phys. Colloques 49 (1988) C8-1221-C8-1222
DOI: 10.1051/jphyscol:19888553

THE PHASE DIAGRAM OF Rb₂Mn_0.7Mg_0.3F₄ IN A MAGNETIC FIELD

R. A. Cowley^{1, 2}, R. J. Birgeneau³, T. Thurston³ et G. Shirane<sup>4

1</sup>  Department of Physics, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, Scotland
²  Now at Clarendon Laboratory, University of Oxford, Oxford, OX1 3P4, G.B.
³  Department of Physics, Massachusetts Institute of Technology, Cambridge, Mass 02139, U.S.A.
⁴  Department of Physics, Brookhaven National Laboratory, Upton, NY 11973, U.S.A.

Abstract
The phase diagram of the quasi-two-dimensional disordered antiferromagnet, Rb₂Mn_0.7Mg_0.3F₄ in a uniform magnetic field along the unique c-axis has been measured using neutron scattering techniques. There are three distinct phases ; at high temperatures the material is paramagnetic, and on cooling in fields above 1.7 T, it undergoes a transition to a spin-flopped phase with long range order perpendicular to the c-axis. The transition temperature decreases with decreasing magnetic field and is below 2 K at 1.75 T. At lower fields there is a phase in which different domain sizes are metastable and the metastability boundary decreases in temperature with increasing field and appears to meet the phase boundary for the spin-flopped phase at T = 0.