Linear magnetic birefringence analysis of the transverse field induced phase transition in hematite

Abstract

The evolutions of the magnetic structure in both pure and manganese-doped single-crystals of hematite have been analyzed near the Morin transition from the use of the linear magnetic birefringence (LMB) at 1.15 micron wavelenght. In pure hematite the LMB shows a very sharp increase over a temperature range ΔT = ±0.1 K around the critical temperature T c. The critical temperature decreases from the Morin temperature T M = 265 K at zero magnetic field to lower temperatures by increasing a transverse field up to 20 kOe applied along a direction perpendicular to the |111| axis. The transverse field induced phase transition is analyzed in detail for temperatures near and lower than the Morin temperature in the pure and doped hematite and is discussed from a theoretical model which accounts for the second and fourth order terms of the anisotropy field.