Low temperature spin reorientation in dysprosium iron garnet

Abstract

The spin reorientation (SR) phase transition in dysprosium iron garnet (Dy3Fe5O12 or DyIG) have been studied by specific heat Cp(T) and high field magnetisation measurements MT(H) and MH(T) on single crystals at low temperature. A first order SR is observed with a sharp jump at TSR = 14.5±0.5 K in the Cp(T) curve which corresponds to a spontaneous change from the high temperature (HT) easy direction ⟨111⟩ to an ⟨uuw⟩ angular low temperature (LT) phases. Above TSR, the magnetic structure is described by the irreducible representation (IR) A2g of the rhombohedral space group R 3 c. Below TSR, the magnetic structure changes in the monoclinic the space group C2/c with the IR Ag. When the field H is kept aligned along the hard symmetry directions ⟨100⟩ and ⟨110⟩, we obtain respectively the variation of the angular positions θ(T) and θ'(T) from the total spontaneous magnetisation down to 1.5 K (θ = 39.23° and θ' = 30.14°) and the results are in good agreement with the previous observations in low fields. When the sample is allowed to rotate freely on itself, the critical field Hc(T) between the HT⟨111⟩ and the LT⟨uuw⟩ angular phases permits us to precise the transition line up to 15 T and 40 K between the so called canted field induced (FI) and the associated collinear magnetic phases. The experimental magnetic phase diagram (MPD) is precisely determined in the (Hc-T) plane and the domains of the existence and the stability of the two magnetic phases are specified.